Induction motor control device and induction motor system

Abstract

To provide an induction motor control device capable of automatically controlling an induction motor by controlling a secondary resistance value of the induction motor on the basis of a control signal, and an induction motor system including the same.SOLUTION: An induction motor system 1000a according to the present invention is a device for controlling an induction motor IM having a primary winding and a secondary winding, and includes a secondary resistance unit RN having a plurality of resistance elements connected in series to the secondary winding for each phase, a switch unit SW having a first electronic switch element for switching whether one of the plurality of resistance elements is effective as a resistance element of the secondary resistance unit RN, and a rounding processing unit RP which is an example of a secondary resistance control unit that controls the resistance value of the secondary resistance unit RN by controlling the on / off of the first electronic switch element on the basis of a predetermined control command.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an induction motor control device that controls an induction motor by controlling the resistance value of a secondary resistance portion in a secondary winding, and an induction motor system including the same.

Background Art

[0002] Induction motors are used, for example, as power sources for various devices such as overhead traveling cranes and pumps. In this induction motor, generally, since the torque of the induction motor is proportional to the square of the primary voltage, an inverter is provided on the primary side of the induction motor, and the voltage of the inverter is controlled based on a control signal, whereby the induction motor is automatically controlled (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, since the torque of the induction motor decreases as the resistance value on the secondary side increases, a plurality of resistance elements are connected in series in multiple stages on the secondary side of the induction motor, and among the plurality of stages of resistance elements, the resistance element of the stage connected to the secondary side of the induction motor is switched by a contact relay (mechanical relay), whereby the induction motor can be controlled. However, the torque fluctuation in the low-speed region is large, and since the contact relay is manually operated, the controllability deteriorates.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an induction motor control device that can automatically control the induction motor by controlling the secondary resistance value of the induction motor based on a control signal, and an induction motor system including the same.

Means for Solving the Problems

[0006] As a result of various studies, the present inventor has found that the above object is achieved by the following present invention. That is, an induction motor control device according to an aspect of the present invention is a device for controlling an induction motor including a primary winding and a secondary winding, and includes a secondary resistor unit including a plurality of resistor elements connected to each phase of the secondary winding and connected in series, a switch unit including a first electronic switch element for switching whether or not each of the plurality of resistor elements is effective as a resistor element of the secondary resistor unit, and a secondary resistor control unit for controlling the resistance value of the secondary resistor unit by controlling on / off of the first electronic switch element based on a predetermined control command. Preferably, in the above-described induction motor control device, the induction motor is a three-phase induction motor, and the first electronic switch element of the switch unit is provided to open or short-circuit the phase between the secondary winding sides of the resistor elements corresponding to the plurality of resistor elements, and switches whether or not each resistor element is effective as a resistor element of the secondary resistor unit by opening or short-circuiting the phase between the phases.

[0007] Such an induction motor control device includes a first electronic switch element for switching whether or not each of the plurality of resistor elements is effective as a resistor element of the secondary resistor unit. Therefore, the resistance value of the secondary resistor unit can be controlled by controlling on / off of the first electronic switch element based on a predetermined control command, and thus the induction motor can be automatically controlled.

[0008] In another aspect, in the above-described induction motor automatic control device, the control command is a notch command representing the number of notches indicating the resistor elements that are effective as the resistor elements of the secondary resistor unit among the plurality of resistor elements, and the secondary resistor control unit rounds the command value of the notch command to an integer and controls the resistance value of the secondary resistor unit by controlling on / off of the first electronic switch element based on the integerized command value.

[0009] Even when the command value of the notch command has a numerical value after the decimal point, such an induction motor control device rounds it up, so that the resistance value of the secondary resistance section can be controlled, and thus the induction motor can be automatically controlled.

[0010] In another aspect, in the above-described induction motor automatic control device, the control command is a notch command representing the number of notches indicating the resistance elements that are valid as the resistance elements of the secondary resistance section among the plurality of resistance elements. The secondary resistance control section obtains first A and first B integers so as to sandwich the command value of the notch command, and determines the first A coefficient and the first B coefficient such that the sum of the first A multiplication result obtained by multiplying the first A coefficient by the first A integer and the first B multiplication result obtained by multiplying the first B coefficient by the first B integer becomes the command value of the notch command. The first on-time obtained by controlling the on / off of the first electronic switch element so that the first A resistance element corresponding to the first A integer among the plurality of resistance elements is valid as the resistance element of the secondary resistance section, and the first B on-time obtained by controlling the on / off of the first electronic switch element so that the first B resistance element corresponding to the first B integer among the plurality of resistance elements is valid as the resistance element of the secondary resistance section, the resistance value of the secondary resistance section is controlled by controlling the on / off of the first electronic switch element so that the ratio becomes the first duty ratio which is the ratio of the obtained first A coefficient and first B coefficient.

[0011] Since such an induction motor control device controls the on / off of the first electronic switch element at the first duty ratio based on the command value of the notch command to control the resistance value of the secondary resistance section, when the command value of the notch command has a numerical value after the decimal point, the resistance value of the secondary resistance section can be controlled with higher accuracy compared to the case of the above-described rounding up, and thus the induction motor can be automatically controlled with higher accuracy.

[0012] In another aspect, in the induction motor automatic control device described above, the control command is a torque command, and when the switching time for switching whether or not it is effective is less than the maximum value of the real part of the eigenvalue of the induction motor, from the plurality of resistance elements, the second A and second B resistance elements are selected so as to sandwich a resistance value corresponding to the command value of the torque command, and the second A multiplication result obtained by multiplying the second A coefficient by the second A resistance value of the second A resistance element and the second B multiplication result obtained by multiplying the second B coefficient by the second B resistance value of the second B resistance element are calculated. The second A and second B coefficients are obtained such that the sum is equal to the resistance value corresponding to the command value of the torque command. Among the plurality of resistance elements, the on / off of the first electronic switch element is controlled so that the second A resistance element is made effective as the resistance element of the secondary resistance part, thereby obtaining a second A on-time, and among the plurality of resistance elements, the on / off of the first electronic switch element is controlled so that the second B resistance element is made effective as the resistance element of the secondary resistance part, thereby obtaining a second B on-time. The on / off of the first electronic switch element is controlled so that the second duty ratio, which is the ratio of the obtained second A coefficient to the second B coefficient, is obtained, thereby controlling the resistance value of the secondary resistance part. Preferably, in the induction motor control device described above, the secondary resistance control unit selects the second A and second B resistance elements so that there is no resistance value of another resistance element between the second A resistance value of the second A resistance element and the second B resistance value of the second B resistance element. Preferably, in the induction motor control device described above, the induction motor further includes a predetermined mechanical mechanism having the induction motor as a power source, and the natural vibration of the induction motor and the mechanical mechanism is 1 / 3 or less of the power supply frequency of the induction motor. Preferably, in the induction motor control device described above, the induction motor further includes a predetermined mechanical mechanism having the induction motor as a power source, and the natural vibration of the induction motor and the mechanical mechanism is 1 / 4 or less of the power supply frequency of the induction motor. Preferably, the natural vibration of the induction motor and the mechanical mechanism is 10 Hz or less. Preferably, in the induction motor control device described above, the induction motor is a three-phase induction motor, and the switch unit connects the first electronic switch so that the secondary resistance part is star-connected.

[0013] Such an induction motor control device controls the on / off of the first electronic switch element at a second duty ratio based on a resistance value corresponding to a command value of a torque command to control the resistance value of the secondary resistance unit, so that the induction motor can be automatically controlled over the entire outputtable torque range in the induction motor.

[0014] In another aspect, in these above-described induction motor automatic control devices, the control command is a torque command, and when the switching time for switching whether or not it is effective is greater than or equal to the maximum value of the real part of the eigenvalue of the induction motor, from the plurality of resistance elements, the third A and third B resistance elements are selected so that the command value of the torque command is sandwiched between the third A output torque of the third A resistance element and the third B output torque of the third B resistance element, the third A and third B coefficients are obtained such that the sum of the third A multiplication result obtained by multiplying the third A coefficient by the third A output torque and the third B multiplication result obtained by multiplying the third B coefficient by the third B output torque becomes the command value of the torque command, and the on / off of the first electronic switch element is controlled so that, among the plurality of resistance elements, the third A resistance element is made effective as the resistance element of the secondary resistance unit, and the third A on-time obtained thereby, and the on / off of the first electronic switch element is controlled so that, among the plurality of resistance elements, the third B resistance element is made effective as the resistance element of the secondary resistance unit, and the third B on-time obtained thereby, are set to a third duty ratio that is the ratio of the obtained third A coefficient to the third B coefficient, and the resistance value of the secondary resistance unit is controlled by controlling the on / off of the first electronic switch element. Preferably, in the above-described induction motor control device, the secondary resistance control unit selects the third A and third B resistance elements so that there is no resistance value of another resistance element between the third A resistance value of the third A resistance element and the third B resistance value of the third B resistance element. Preferably, in the above-described induction motor control device, the induction motor is a three-phase induction motor, and the switch unit connects the first electronic switch so that the secondary resistance unit is in a star connection.

[0015] Such an induction motor control device controls the on / off of the first electronic switch element at a third duty ratio based on the command value of the torque command to control the resistance value of the secondary resistance section, so that the induction motor can be automatically controlled over the entire outputtable torque range in the induction motor.

[0016] In another aspect, in the above-described induction motor automatic control device, a second electronic switch element for opening or short-circuiting the phases of the secondary winding is provided, and an insulation state forming section for opening the phases of the secondary winding by turning off the second electronic switch element to make the phases of the secondary winding in an insulated state is further provided.

[0017] Such an induction motor control device further includes an insulation state forming section, so that it can output at low torque in the low-speed region and can improve controllability in the low-speed region.

[0018] In another aspect, in the above-described induction motor automatic control device, the second electronic switch element is a thyristor.

[0019] Such an induction motor control device can suppress the surge voltage (current) that may occur when opening the phases of the secondary winding to make the phases of the secondary winding in an insulated state and can reduce noise by using a thyristor for the second electronic switch element.

[0020] In another aspect, in the above-described induction motor automatic control device, the first electronic switch element is a thyristor.

[0021] Such an induction motor control device can further suppress the surge voltage (current) and reduce the noise by using a thyristor for the first electronic switch element.

[0022] In another aspect, in the induction motor automatic control device described above, the induction motor is a three-phase induction motor, and the secondary resistance control unit sets the on-off cycle of each thyristor of the first and second electronic switch elements to any value within a range of 3 [Hz] or more and 10 [Hz] or less in terms of frequency, or sets the on-off cycle of each thyristor of the first and second electronic switch elements to a value that is an odd multiple of a half cycle of the primary side power supply frequency that supplies power to the primary winding.

[0023] Such an induction motor control device can suppress the offset of each phase current and suppress the deviation between the command value of the torque command and the output torque.

[0024] In another aspect, in the induction motor automatic control device described above, the induction motor is a three-phase induction motor, and the secondary resistance control unit makes the on-time of each thyristor of the first and second electronic switch elements shorter than the target on-time.

[0025] Although a thyristor may have a delayed off-timing because it turns off at a current of 0, the above induction motor control device can compensate for the delay in the off-timing and improve the controllability by making it shorter than the target on-time based on the control command.

[0026] In another aspect, in the induction motor automatic control device described above, a second electronic switch element for opening or short-circuiting the phases of the secondary winding is provided, and an insulation state forming unit for opening the phases of the secondary winding and making the phases of the secondary winding in an insulated state by turning off the second electronic switch element is further provided.

[0027] If the insulation state and the effective state having the resistance element are controlled by a second duty ratio based on the resistance value corresponding to the command value of the torque command, the resistance value of the secondary resistance unit will become infinite, and thus the induction motor cannot be automatically controlled. However, the above induction motor control device controls the insulation state and the effective state having the resistance element by a third duty ratio based on the command value of the torque command, so the induction motor can be automatically controlled.

[0028] In another aspect, in the above-described induction motor automatic control device, the induction motor is a three-phase induction motor having U-phase, V-phase, and W-phase, and a first connection state in which each of the U-phase and V-phase of the power supply is connected to each of the U-phase and V-phase in the primary winding of the induction motor, and a second connection state in which each of the U-phase and V-phase of the power supply is connected to each of the V-phase and U-phase in the primary winding of the induction motor. A forward-reverse switch unit for switching, and a hold unit for holding a switching command for switching the connection state of the forward-reverse switch unit for a time longer than the switching required time required for switching the connection state in the forward-reverse switch unit. The forward-reverse switch unit is input with the switching command via the hold unit.

[0029] Even when it takes time to switch the connection state in the forward-reverse switch unit, such an induction motor control device holds the switching command in the hold unit, so that the connection state in the forward-reverse switch unit can be surely switched.

[0030] An induction motor system according to another aspect of the present invention is a system including an induction motor having a primary winding and a secondary winding, and an induction motor control device for controlling the induction motor, wherein the induction motor control device is any of the above-described induction motor control devices.

[0031] According to this, an induction motor system including any of the above-described induction motor control devices can be provided.

Advantages of the Invention

[0032] The induction motor control device according to the present invention can automatically control the induction motor by controlling the secondary resistance value of the induction motor based on a control signal. According to the present invention, an induction motor system including such an induction motor control device can be provided.

Brief Description of the Drawings

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[0034] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted as appropriate. In this specification, when referring to components in general, reference numerals without subscripts are used, and when referring to individual components, reference numerals with subscripts are used.

[0035] The induction motor system in the embodiment includes an induction motor having a primary winding and a secondary winding, and an induction motor control device for controlling the induction motor. This induction motor control device includes a secondary resistance unit having a plurality of resistance elements connected to the secondary winding for each phase and connected in series, and a first electronic switch element for switching whether or not the resistance element of the secondary resistance unit is effective among the plurality of resistance elements. And a secondary resistance control unit that controls the resistance value of the secondary resistance unit by controlling the on / off of the first electronic switch element based on a predetermined control command. Hereinafter, such an induction motor system and an induction motor control device will be described more specifically by the first to third embodiments.

[0036] First, the induction motor system and the induction motor control device in the first embodiment will be described.

[0037] FIG. 1 is a block diagram showing the configuration of an induction motor system according to the first embodiment. FIG. 2 is a circuit diagram mainly of an induction motor and a secondary resistance part and a switch part in the induction motor control device in the induction motor system. Note that FIG. 2 is also a circuit diagram mainly of an induction motor and a secondary resistance part and a switch part in each induction motor system of the second and third embodiments described later, not only the first embodiment. FIG. 3 is a graph for showing the torque-speed characteristics in the induction motor system of the first embodiment as an example. The horizontal axis of FIG. 3 is the electrical angular velocity [rad / s], and the vertical axis thereof is the torque [Nm].

[0038] The induction motor system 1000a in the first embodiment includes, for example, as shown in FIG. 1, a position velocity FB control unit PVC, a notch forward / reverse control unit NRC, a rounding processing unit RP, an induction motor unit IMU, and a position velocity sensor PVS, and drives a mechanical system MS such as an overhead traveling crane or a pump, for example.

[0039] The induction motor unit IMU includes, for example, as shown in FIG. 2, an induction motor IM, a secondary resistance part RN (RN1 to RN3), a switch part SW (SW1 to SW3), and a forward / reverse switch part RS, and is powered from a primary power supply Vcc which is a primary side power supply.

[0040] The induction motor IM may be a single-phase induction motor, but in the example shown in FIG. 2, it is a three-phase induction motor having U-phase, V-phase, and W-phase. For this reason, in the example shown in FIG. 2, the primary power supply Vcc is, for example, a commercial power supply that supplies three-phase AC power. The induction motor IM includes first to third coils L1a, R1a; L1b, R1b; L1c, R1c corresponding to each phase, which serve as the primary winding, and first to third coils L2a, R2a; L2b, R2b; L2c, R2c corresponding to each phase, which serve as the secondary winding. In FIG. 2, the first coil L1a, R1a is illustrated as a model of a series connection of an inductor L1a representing its inductance component and a resistor element R1a representing its impedance component. The second and third coils L1b, R1b; L1c, R1c are also illustrated in a similar model, and the first to third coils L2a, R2a; L2b, R2b; L2c, R2c are also illustrated in a similar model. The primary winding is provided in a stator, and the secondary winding is provided in a rotor. In the induction motor IM, a rotating magnetic field is formed by the three-phase AC power supplied to the primary winding of the stator, and the rotor rotates due to the interaction between the magnetic field generated by the induced electromotive force generated in the secondary winding of the rotor by this rotating magnetic field and the rotating magnetic field.

[0041] The secondary resistor section RN is a circuit that is connected to each phase of the secondary winding and includes a plurality of resistor elements connected in series in multiple stages. In the example shown in FIG. 2, as described above, since the induction motor IM is a three-phase induction motor, for each phase, a plurality of resistor elements connected in series in multiple stages are connected. More specifically, one end of each of the first to third coils L1a, R1a; L1b, R1b; L1c, R1c of each phase in the induction motor IM is connected to each other, and the other ends thereof are drawn out via, for example, a slip ring SR and connected to the secondary resistor section RN. The secondary resistor section RN is configured to include three stages of first to third stages RN1 to RN3. The first stage RN1 includes three first to thirteenth resistor elements RN1a, RN1b, RN1c having the same resistance value provided corresponding to each phase. Similarly, the second stage RN2 includes three second to twenty-third resistor elements RN2a, RN2b, RN2c having the same resistance value provided corresponding to each phase, and the third stage RN3 includes three third to thirty-third resistor elements RN3a, RN3b, RN3c having the same resistance value provided corresponding to each phase. One end of the first eleventh resistor element RN1a, the second eleventh resistor element RN2a, and the third eleventh resistor element RN3a connected in series is connected to, for example, the U phase drawn out to the slip ring SR. One end of the first twelfth resistor element RN1b, the second twelfth resistor element RN2b, and the third twelfth resistor element RN3b connected in series is connected to, for example, the V phase drawn out to the slip ring SR. One end of the first thirteenth resistor element RN1c, the second thirteenth resistor element RN2c, and the third thirteenth resistor element RN3c connected in series is connected to, for example, the W phase drawn out to the slip ring SR. The other ends of the first eleventh resistor element RN1a, the second eleventh resistor element RN2a, and the third eleventh resistor element RN3a connected in series, the other ends of the first twelfth resistor element RN1b, the second twelfth resistor element RN2b, and the third twelfth resistor element RN3b connected in series, and one end of the first thirteenth resistor element RN1c, the second thirteenth resistor element RN2c, and the third thirteenth resistor element RN3c connected in series are connected to each other.

[0042] The switch unit SW is a circuit including a first electronic switch element for switching whether or not a resistor element of the secondary resistor unit RN is effective among the plurality of resistor elements. In the example shown in FIG. 2, as described above, since the induction motor IM is a three-phase induction motor, the first electronic switch element of the switch unit SW is provided corresponding to each of the plurality of resistor elements so as to open or short-circuit the phases on the secondary winding side of the resistor element, and switches whether or not the resistor element of the secondary resistor unit is effective by opening or short-circuiting the phases. More specifically, the switch unit SW includes an electronic switch element for opening or short-circuiting the phases for each phase, provided on the secondary winding side of each stage in the multi-stage secondary resistor unit RN. More specifically, in the example shown in FIG. 2, as described above, the secondary resistor unit RN is configured to include three stages, a first to a third stage RN1 to RN3. On the secondary winding side of the first stage RN1, a first switch unit SW1 of the switch unit SW including three first to thirteenth electronic switch elements Tr1a, Tr1b, Tr1c for opening or short-circuiting the phases is provided for each phase. On the secondary winding side of the second stage RN2, a second switch unit SW2 of the switch unit SW including three twenty-first to twenty-third electronic switch elements Tr2a, Tr2b, Tr2c for opening or short-circuiting the phases is provided for each phase. On the secondary winding side of the third stage RN3, a third switch unit SW3 of the switch unit SW including three thirty-first to thirty-third electronic switch elements Tr3a, Tr3b, Tr3c for opening or short-circuiting the phases is provided for each phase. In the first switch unit SW1, the first eleventh electronic switch element Tr1a is provided between the U and V phases and opens or short-circuits the U and V phases. The first twelfth electronic switch element Tr1b is provided between the V and W phases and opens or short-circuits the V and W phases. The first thirteenth electronic switch element Tr1c is provided between the W and U phases and opens or short-circuits the W and U phases. Similarly, in the second switch unit SW2, the second twenty-first electronic switch element Tr2a is provided between the U and V phases and opens or short-circuits the U and V phases. The second twenty-second electronic switch element Tr2b is provided between the V and W phases and opens or short-circuits the V and W phases. The second twenty-third electronic switch element Tr2c is provided between the W and U phases and opens or short-circuits the W and U phases.Similarly, in the third switch section SW3, the 31st electronic switch element Tr3a is provided between the U and V phases, opens or shorts the U and V phases, the 32nd electronic switch element Tr3b is provided between the V and W phases, opens or shorts the V and W phases, and the 33rd electronic switch element Tr3c is provided between the W and U phases, opens or shorts the W and U phases. Each of the electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c is configured to include, for example, two first and second transistors. The collector of the first transistor and the emitter of the second transistor are connected to each other and connected to one phase in the phase where the electronic switch element Tr is provided. The emitter of the first transistor and the collector of the second transistor are connected to each other and connected to the other phase in the phase where the electronic switch element Tr is provided. The bases of the first transistor and the second transistor are connected to each other and drawn out as a control terminal to which an on / off control signal is input, and connected to the rounding processing section RP.

[0043] Here, the notch command, which is an example of a control command, represents the number of notches indicating the resistive elements that are effective as the resistive elements of the secondary resistor section RN among the plurality of resistive elements in the secondary resistor section RN. In other words, it represents the number of notches indicating the stages that are effective as the resistive elements of the secondary resistor section RN among the multiple stages in the secondary resistor section RN. In the example shown in FIG. 2, when the first to third stages RN1 to RN3 are effective as the resistive elements of the secondary resistor section RN, it is called "1 notch". When the notch command is "1" (1 notch), each electronic switch element Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c in the first to third switch sections SW1 to SW3 is turned off. When the first stage RN1 is not effective (invalid) as the resistive element of the secondary resistor section RN and the second and third stages RN2 and RN3 are effective as the resistive elements of the secondary resistor section RN, it is called "2 notches". When the notch command is "2" (2 notches), each electronic switch element Tr1a to Tr1c in the first switch section SW1 is turned on, and each electronic switch element Tr2a to Tr2c; Tr3a to Tr3c in the second and third switch sections SW2 and SW3 is turned off. When the first and second stages RN1 and RN2 are not effective (invalid) as the resistive elements of the secondary resistor section RN and the third stage RN3 is effective as the resistive element of the secondary resistor section RN, it is called "3 notches". When the notch command is "3" (3 notches), each electronic switch element Tr1a to Tr1c; Tr2a to Tr2c in the first and second switch sections SW1 and SW2 is turned on, and each electronic switch element Tr3a to Tr3c in the third switch section SW2 and SW3 is turned off. When the first to third stages RN1 to RN3 are not effective (invalid) as the resistive elements of the secondary resistor section RN, it is called "4 notches". When the notch command is "4" (4 notches), each electronic switch element Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c in the first to third switch sections SW1 to SW3 is turned on. Therefore, in the case of 4 notches, the resistance value of the secondary winding becomes the impedance components R2a; R2b; R2c in the first to third coils L2a, R2a; L2b, R2b; L2c, R2c.

[0044] The resistance value of the 1-notch is greater than that of the 2-notch, the resistance value of the 2-notch is greater than that of the 3-notch, and the resistance value of the 3-notch is greater than that of the 4-notch. If this condition is satisfied, the resistance values of each stage RN1 to RN3 may be the same or different.

[0045] The forward and reverse switch section RS is a switch circuit that switches between forward rotation and reverse rotation in the induction motor IM. More specifically, the forward and reverse switch section RS is provided between the primary power supply Vcc and, for example, the U-phase and V-phase of the primary winding, and connects each of the U-phase and V-phase of the primary power supply Vcc to each of the U-phase and V-phase in the primary winding of the induction motor in a first connection state, and each of the U-phase and V-phase of the primary power supply Vcc to each of the V-phase and U-phase in the primary winding of the induction motor in a second connection state, and switches based on a switching command (switching control signal) from the notch forward and reverse control section NRC. The W-phase of the primary power supply Vcc is connected to the W-phase of the primary winding. The forward and reverse switch section RS is configured to include, for example, a contact relay.

[0046] Returning to FIG. 1, the position and velocity sensor PVS includes a position sensor and an angular velocity sensor, measures the position and angular velocity of the induction motor IM respectively, outputs the measured position and angular velocity to the position velocity FB control section PVC, and outputs the measured angular velocity to the rounding processing section RP.

[0047] The position and velocity feedback control unit PVC compares, for example, the position and velocity commands (target position, target angular velocity) input from a higher-level system, an input device, etc., with the position and angular velocity measured by the position and velocity sensor PVS, generates a control command so as to eliminate these deviations, and outputs the generated control command to the rounding processing unit RP. The position and velocity feedback control unit PVC performs feedback control, for example, by PID control. In the first embodiment, the control command is a notch command. For example, the correspondence between the control command and the notch command is prepared in advance and stored in a storage unit (not shown) of the induction motor system 1000a. The position and velocity feedback control unit PVC converts the control command into a notch command based on this correspondence. The control command (notch command) also includes the rotation direction of the induction motor IM. The position and velocity feedback control unit PVC outputs the notch command to the notch forward and reverse control unit NRC and the rounding processing unit RP, respectively. For example, the rotation direction is represented by the sign of the number of notches. When the command value of the notch command is a positive number of notches, it means forward rotation, and when the command value of the notch command is a negative number of notches, it means reverse rotation.

[0048] The notch forward / reverse control unit NRC is a device (circuit) that generates a switching command based on a control command (notch command) from the position and speed FB control unit PVC and outputs the generated switching command to the forward / reverse switch unit RS. More specifically, the notch forward / reverse control unit NRC stores the current connection state in the forward / reverse switch unit RS, and when the rotation direction according to the stored current connection state is different from the rotation direction according to the control command (notch command) from the position and speed FB control unit PVC, it generates a switching command to switch to the connection state corresponding to the rotation direction according to the control command (notch command) from the position and speed FB control unit PVC, and outputs the generated switching command to the forward / reverse switch unit RS. For example, when the rotation direction according to the stored current connection state is forward rotation and the rotation direction according to the control command (notch command) from the position and speed FB control unit PVC is reverse rotation, the notch forward / reverse control unit NRC generates a switching command to switch to the reverse connection state and outputs the generated switching command to the forward / reverse switch unit RS. On the other hand, when the rotation direction according to the stored current connection state is forward rotation and the rotation direction according to the control command (notch command) from the position and speed FB control unit PVC is forward rotation, the notch forward / reverse control unit NRC does not generate a switching command and does not output it.

[0049] The rounding processing unit RP is a device (circuit) that rounds the command value of a notch command, which is an example of a control command, to an integer, and controls the on / off of the first electronic switching element based on the rounded command value, thereby controlling the resistance value of the secondary resistance unit RN. The rounding processing unit RP is connected to each control terminal of each first electronic switching element in the switch unit SW, and outputs an on / off control signal for controlling the resistance value of the secondary resistance unit RN to each control terminal of each first electronic switching element in the switch unit SW. More specifically, the rounding processing unit RP rounds the absolute value of the command value of the notch command to an integer, and controls the on / off of each first electronic switch in each stage of the secondary resistance unit RN by the on / off control signal so that the rounded command value becomes the number of notches. For example, when the command value of the notch command is "2.4", the command value of the notch command is rounded to "2" (2 notches), and the rounding processing unit RP turns on each first electronic switching element Tr1a~Tr1c in the first switch unit SW1 and turns off each first electronic switching element Tr2a~Tr2c; Tr3a~Tr3c in the second and third switch units SW2, SW3, so as to control the on / off of each first electronic switching element Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c in each stage RN1~RN3. As a result, the resistance value of the secondary resistance unit RN becomes the resistance value of 2 notches, and the induction motor IM is driven according to the torque-speed characteristic in the case of 2 notches. Alternatively, for example, when the command value of the notch command is "2.8", the command value of the notch command is rounded to "3" (3 notches), and the rounding processing unit RP turns on each electronic switching element Tr1a~Tr1c; Tr2a~Tr2c in the first and second switch units SW1, SW2 and turns off each electronic switching element Tr3a~Tr3c in the third switch unit SW2, SW3, so as to control the on / off of each first electronic switching element Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c in each stage RN1~RN3. As a result, the resistance value of the secondary resistance unit RN becomes the resistance value of 3 notches, and the induction motor IM is driven according to the torque-speed characteristic in the case of 3 notches.

[0050] FIG. 3 shows, as an example, a graph of torque-speed characteristics in the induction motor system 1000a of the first embodiment. In the example shown in this FIG. 3, in the electrical angular velocity region below the electrical angular velocity of 170 [rad / s] where the torque-speed characteristic α3 of 3 notches and the torque-speed characteristic α4 of 4 notches intersect, since the output torque at 4 notches is smaller than the output torque at 3 notches, if the induction motor system 1000a is designed on the premise that the output torque of the upper notch is larger than the output torque of the lower notch, in the electrical angular velocity region below the electrical angular velocity of 170 [rad / s], the rounding processing unit RP is designed so as not to use 4 notches. In other words, in the electrical angular velocity region where the output torque of the upper notch is smaller than the output torque of the lower notch, the rounding processing unit RP is designed so as not to use the upper notch.

[0051] Note that the rounding processing unit RP corresponds to another example of a secondary resistance control unit that controls the resistance value of the secondary resistance unit by controlling the on / off of the first electronic switch element based on a predetermined control command.

[0052] As described above, the induction motor system 1000a in the first embodiment and the induction motor control device provided therein include the first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c for switching whether or not to be effective as the resistance elements of the secondary resistance unit RN among the plurality of resistance elements RN1a, RN1b, RN1c; RN2a, RN2b, RN2c; RN3a, RN3b, RN3c in the secondary resistance unit RN. Therefore, the resistance value of the secondary resistance unit RN can be controlled by controlling the on / off of the first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c based on a predetermined control command (here, a notch command), and thus, the induction motor IM can be automatically controlled.

[0053] The above induction motor system 1000a and the induction motor control device can control the resistance value of the secondary resistance part RN because they integerize even when the command value of the notch command has a numerical value below the decimal point. Therefore, the induction motor IM can be automatically controlled.

[0054] FIG. 4 is a graph showing the position-velocity control characteristics in a load state in the induction motor system of the first embodiment as an example. FIG. 5 is a graph showing the position-velocity control characteristics in a load state in the induction motor system of a comparative example as an example. FIG. 6 is a graph showing the position-velocity control characteristics in a no-load state using 1 to 4 notches in the induction motor system of the first embodiment as an example. FIG. 7 is a graph showing the position-velocity control characteristics in a no-load state using 0 to 4 notches in the induction motor system of the first embodiment as an example. FIG. 8 is a graph showing the position-velocity control characteristics in a no-load state in the induction motor system of a comparative example as an example. In FIGS. 4 to 8, FIG. A is a graph of the time change of the position, the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the position. FIG. B is a graph of the time change of each of the command value of the notch command and the actual notch (actual number of notches), the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the notch (number of notches). In FIG. B, the command value of the notch command is represented by a broken line, and the actual notch is represented by a solid line. FIG. 9 is a graph showing the position-velocity control characteristics when a carriage with a large frictional force is driven by the induction motor of the induction motor system of the first embodiment as an example. FIG. 10 is a graph showing the position-velocity control characteristics when a carriage with a large frictional force is driven by the induction motor of the induction motor system of a comparative example as an example. In FIGS. 9 and 10, FIG. A is a graph of the time change of the notch command, the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the notch (number of notches). In FIG. A, PID (output of the position-velocity FB control unit PVC, command value of the notch command before integerization) is represented by a relatively thick solid line, and the notch command (output of the rounding processing unit RP, command value of the notch command after integerization) is represented by a relatively thin solid line. FIG. B is a graph of the time change of the carriage position, the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the carriage position.

[0055] As an example, FIG. 4 shows a graph of the position speed control characteristics in the load state in the induction motor system 1000a of the first embodiment. As an example of this comparative example, FIG. 5 shows a graph of the position speed control characteristics in the load state in the induction motor system of the comparative example. In the induction motor system of this comparative example, a contact relay is used instead of the first electronic switch element. The same applies to FIGS. 8 and 10 described later.

[0056] In the step response of the position in the load state in the induction motor system 1000a of the first embodiment, as shown in FIG. 4, since it is in the load state, 0 notch (output torque is 0) is not used, and 1 notch to 4 notches are used, and the position can be stably stopped at the target position "1". Here, the 0 notch is realized by turning on and off the power supply by the primary power supply Vcc. On the other hand, in the step response of the position in the load state of the comparative example, as shown in FIG. 5, due to the back-and-forth movement between 1 notch and 2 notches, the response is slow, and the position fluctuates around the target position "1".

[0057] Also, as an example, a graph of the position speed control characteristics in the no-load state using 1 notch to 4 notches in the induction motor system 1000a of the first embodiment is shown in FIG. 6, and a graph of the position speed control characteristics in the no-load state using 0 notch to 4 notches in the induction motor system 1000a of the first embodiment is shown in FIG. 7, and a graph of the position speed control characteristics in the no-load state in the induction motor system of the comparative example is shown in FIG. 8.

[0058] In the step response of the position in the no-load state, since it is in the no-load state, the output torque becomes 0, and it is controlled while moving back and forth between ±1 notch. As shown in FIGS. 6 and 8, in each step response of the position in the no-load state of the induction motor system 1000a of the first embodiment and the induction motor system of the comparative example, the position fluctuates around the target position "1". Due to turning on and off the contact relay of the forward and reverse switch section RS, the response is slow.

[0059] Here, instead of realizing zero notch on the primary side, as will be described later, a second electronic switch element is provided to open or short-circuit the phases of the secondary winding in order to realize zero notch on the secondary side. When the second electronic switch element is turned off to open the phases of the secondary winding and make the phases of the secondary winding in an insulated state, as shown in FIG. 7, in each step response of the position in the no-load state in the induction motor system 1000a of the first embodiment, the wobbly position fluctuations as shown in FIG. 6 are improved.

[0060] Also, as an example, a graph of the position-velocity control characteristics when a carriage with a large frictional force is driven by the induction motor IM of the induction motor system 1000a of the first embodiment is shown in FIG. 9, and a graph of the position-velocity control characteristics when a carriage with a large frictional force is driven by the induction motor of the induction motor system of the comparative example is shown in FIG. 10. Note that zero notch is also realized on the secondary side in the case shown in FIG. 9.

[0061] In the induction motor system 1000a of the first embodiment, as shown in FIG. 9, the carriage position smoothly converges to the target carriage position without losing to the frictional force. On the other hand, in the induction motor system of the comparative example, as shown in FIG. 10, the carriage position repeatedly moves back and forth near the target carriage position due to the frictional force, and the carriage position cannot stop at the target carriage position.

[0062] Next, the induction motor system and the induction motor control device in the second embodiment will be described.

[0063] FIG. 11 is a block diagram showing the configuration of the induction motor system in the second embodiment.

[0064] In the first embodiment, the command value of the notch command is integerized, and the resistance value of the secondary resistor RN is controlled at the notch corresponding to the integerized number of notches. However, in the second embodiment, consecutive first and second integers are obtained so as to sandwich the command value of the notch command, and the resistance value of the secondary resistor RN is controlled by moving back and forth between two notches corresponding to the obtained first and second integers at a first duty ratio based on the command value of the notch command.

[0065] The induction motor system 1000b in this second embodiment includes, for example, as shown in FIG. 11, a position velocity FB control unit PVC, a notch forward / reverse control unit NRC, a hold unit HL, a duty ratio control unit DTCb, an induction motor unit IMU, and a position velocity sensor PVS, and drives a mechanical system MS such as an overhead traveling crane or a pump. The induction motor unit IMU of this second embodiment includes a secondary resistor RN, but in the induction motor unit IMU shown in FIG. 11, this secondary resistor RN is omitted for illustration purposes.

[0066] The position velocity FB control unit PVC, the notch forward / reverse control unit NRC, the induction motor unit IMU, and the position velocity sensor PVS in the induction motor system 1000b of this second embodiment are the same as the position velocity FB control unit PVC, the notch forward / reverse control unit NRC, the induction motor unit IMU, and the position velocity sensor PVS in the induction motor system 1000a of the first embodiment, respectively, and thus their descriptions are omitted.

[0067] The holding unit HL is a device (circuit) that holds a switching command (switching control signal) for switching the connection state of the forward / reverse switch unit RS from the notch forward / reverse control unit NRC for a time longer than the switching required time for switching the connection state in the forward / reverse switch unit RS. The switching command is input to the forward / reverse switch unit RS via the holding unit HL. In the forward / reverse switch unit RS, the connection state is surely switched by the switching command from the holding unit HL. In the present embodiment, the holding unit HL also outputs to the switch unit SW, and each first electronic switch element Tr in the switch unit SW maintains the current on / off state while the forward / reverse switch unit RS has the switching command held by the holding unit HL and the connection state is switched. Thereby, while the connection state of the forward / reverse switch unit RS is being switched, the current first duty ratio is maintained, and the switch unit SW can cope with the response delay of the forward / reverse switch unit RS.

[0068] The duty ratio control unit DTCb obtains first A and first B integers n and m so as to sandwich the command value Nd of a notch command as an example of a control command, and the sum DAn×n + DAm×m of a first A multiplication result DAn×n obtained by multiplying the first A coefficient DAn by the first A integer n and a first B multiplication result DAm×m obtained by multiplying the first B coefficient DAm by the first B integer m becomes the command value Nd (= DAn×n + DAm×m) of the notch command, and obtains the first A and first B coefficients DAn and DAm (DAn = (m - Nd) / (m - n) = 1 - DAm, DAm = (Nd - n) / (m - n) = 1 - DAn, provided that n < m). Among the plurality of resistance elements, a first A on-time Tn by controlling the on / off of the first electronic switch element so as to enable a first A resistance element (the notch of the first A integer n (n notch)) corresponding to the first A integer n as a resistance element of the secondary resistance unit, and a first B on-time Tm by controlling the on / off of the first electronic switch element so as to enable a first B resistance element (the notch of the first B integer m (m notch)) corresponding to the first B integer m as a resistance element of the secondary resistance unit are controlled such that the on / off of the first electronic switch element is controlled so that the first duty ratio DAn:DAm (= Tn:Tm), which is the ratio of the obtained first A coefficient DAn and first B coefficient DAm, becomes the resistance value of the secondary resistance unit.

[0069] Therefore, the duty ratio control unit DTCb first obtains the first A and first B integers n and m so as to sandwich the command value Nd of the notch command. For example, when the command value of the notch command is 2.4, the duty ratio control unit DTCb selects, for example, 2 notches and 3 notches. Alternatively, for example, the duty ratio control unit DTCb may select 2 notches and 4 notches, or for example, may select 1 notch and 3 notches, or for example, may select 1 notch and 4 notches. When there are a plurality of selectable combinations, any of the plurality of selectable combinations may be selected. Since the current will flow back and forth between the first A resistor element with n notches and the first B resistor element with m notches at the first duty ratio DAn:DAm, it is preferable that the fluctuation of the resistance value is small. Therefore, it is preferable to select a combination in which the number of notches is continuous. In other words, the duty ratio control unit DTCc preferably selects the first A and first B resistor elements so that there is no resistance value of another resistor element between the first A resistance value Rn of the first A resistor element and the first B resistance value Rm of the first B resistor element.

[0070] Subsequently, the duty ratio control unit DTCb obtains the first A and first B coefficients DAn and DAm according to DAn = (m - Nd) / (m - n) = 1 - DAm, DAm = (Nd - n) / (m - n) = 1 - DAn, and obtains the first duty ratio DAn:DAm.

[0071] Then, the duty ratio control unit DTCb controls the on / off of the first electronic switch element so that, among the plurality of resistance elements in the secondary resistance unit RN, the first A resistance element corresponding to the first A integer n is made effective as the resistance element of the secondary resistance unit RN, thereby obtaining a first A on-time Tn, and controls the on / off of the first electronic switch element so that, among the plurality of resistance elements, the first B resistance element corresponding to the first B integer m is made effective as the resistance element of the secondary resistance unit, thereby obtaining a first B on-time Tm. The resistance value of the secondary resistance unit is controlled by controlling the on / off of the first electronic switch element so that the first duty ratio DAn:DAm (= Tn:Tm), which is the ratio of the obtained first A coefficient DAn to the first B coefficient DAm, is achieved. In other words, the duty ratio control unit DTCb controls the on / off of the first electronic switch element in the secondary resistance unit RN so that the first A on-time Tn with the secondary resistance unit RN having n notches and the first B on-time Tm with the secondary resistance unit RN having m notches result in the first duty ratio DAn:DAm (= Tn:Tm). In the example shown in FIG. 2, the duty ratio control unit DTCb controls the on / off of the first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c of each switch unit SW1 to SW3 corresponding to each stage RN1 to RN3 in the secondary resistance unit RN so that DAn:DAm = Tn:Tm. Thereby, the secondary resistance unit RN is controlled so that the resistance value of the secondary resistance unit RN becomes the command value Nd of the notch command.

[0072] Note that the duty ratio control unit DTCb corresponds to another example of a secondary resistance control unit that controls the resistance value of the secondary resistance unit by controlling the on / off of the first electronic switch element based on a predetermined control command.

[0073] FIG. 12 is a graph showing the position speed control characteristics in the load state in the induction motor system of the second embodiment as an example. FIG. 13 is a graph showing the position speed control characteristics in the no-load state using 0 to 4 notches in the induction motor system of the second embodiment as an example. In FIGS. 12 and 13, FIG. A is a graph of the time change of the position, the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the position. FIG. B is a graph of each time change of the command value of the notch command and the actual notch (actual number of notches), the horizontal axis of which is time (elapsed time) [s], and the vertical axis of which is the notch (number of notches). In FIG. B, the command value of the notch command is represented by a broken line, and the actual notch is represented by a solid line. Here, in the case of 0 notch, 0 notch is realized on the secondary side in the same manner as in FIG. 7 described above.

[0074] In the step response of the position in the load state in the induction motor system 1000b of the second embodiment, as shown in FIG. 12, the notch is continuously and smoothly changed by the control based on the first duty ratio DAn:DAm, and the positioning can be controlled with high precision including the transient response.

[0075] In the step response of the position in the no-load state using 0 to 4 notches in the induction motor system of the second embodiment, 0 notch is realized on the secondary side, and as shown in FIG. 13, a fine output torque can be realized in the low torque region of the low speed region by the control based on the first duty ratio DAn:DAm, and high-precision position and speed control can be realized.

[0076] As described above, the induction motor system 1000b in the second embodiment and the induction motor control device provided therein include first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c for switching whether or not the plurality of resistance elements RN1a, RN1b, RN1c; RN2a, RN2b, RN2c; RN3a, RN3b, RN3c in the secondary resistance unit RN are effective as resistance elements of the secondary resistance unit RN. Therefore, by controlling the on / off of the first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c based on a predetermined control command (here, a notch command), the resistance value of the secondary resistance unit RN can be controlled, and thus, the induction motor IM can be automatically controlled.

[0077] The above induction motor system 1000b and induction motor control device control the on / off of the first electronic switch elements Tr1a to Tr1c; Tr2a to Tr2c; Tr3a to Tr3c with a first duty ratio DAn: DAm based on the command value of the notch command to control the resistance value of the secondary resistance unit RN. Therefore, when the command value of the notch command has a numerical value after the decimal point, the resistance value of the secondary resistance unit RN can be controlled with higher accuracy compared to the case of integerization described above. Thus, the induction motor IM can be automatically controlled with higher accuracy.

[0078] Next, the induction motor system and the induction motor control device in the third embodiment will be described.

[0079] FIG. 14 is a block diagram showing the configuration of the induction motor system according to the third embodiment. FIG. 15 is a graph showing torque-speed characteristics in the case of controlling with a second duty ratio based on a resistance value corresponding to a command value of a torque command in the induction motor system of the third embodiment as an example. FIG. 16 is a graph showing torque-speed characteristics in the case of controlling with a second duty ratio based on a resistance value corresponding to a command value of a torque command in the induction motor system of the third embodiment as another example. FIG. 17 is a graph showing torque-speed characteristics in the case where the command value of the torque command is the maximum output torque in the induction motor system of the third embodiment as an example. In FIGS. 15 to 17, each horizontal axis represents the electrical angular velocity [rad / s], and each vertical axis represents the torque [Nm]. FIG. 18 is a graph showing the response characteristics of each output torque in the case of a step change from 1 notch to 1.5 notches and in the case of a step change from 1.5 notches to 2 notches in the induction motor system of the third embodiment as an example. FIG. 18A shows the case of a step change from 1 notch to 1.5 notches, and FIG. 18B shows the case of a step change from 1.5 notches to 2 notches. FIG. 19 is a graph showing the response characteristics of each output torque in the case of a step change from 2 notches to 2.5 notches and in the case of a step change from 2.5 notches to 3 notches in the induction motor system of the third embodiment as an example. FIG. 19A shows the case of a step change from 2 notches to 2.5 notches, and FIG. 19B shows the case of a step change from 2.5 notches to 3 notches. FIG. 20 is a graph showing the response characteristics of the output torque in the case of a step change from 3 notches to 3.5 notches in the induction motor system of the third embodiment as an example. FIG. 21 is a graph showing the response characteristics of the output torque in the case of a step change from 3 notches to 3.5 notches at an electrical angular velocity of 150 [rad / s] in the induction motor system of the third embodiment as an example. In each of FIGS. 18 to 21, the horizontal axis represents time (elapsed time) [s], and the vertical axis represents torque [Nm]. FIG. 22 is a graph showing torque-speed characteristics when controlling with a third duty ratio based on the command value of a torque command between 3 notches and 4 notches, as an example, in the induction motor system of the third embodiment. FIG. 23 is a graph showing torque-speed characteristics when controlling with a third duty ratio based on the command value of a torque command between 2 notches and 3 notches, as an example, in the induction motor system of the third embodiment. FIG. 24 is a graph showing torque-speed characteristics when controlling with a third duty ratio based on the command value of a torque command between 1 notch and 3 notches, as an example, in the induction motor system of the third embodiment. In FIGS. 22 to 24, the horizontal axis represents electrical angular velocity [rad / s], and the vertical axis represents torque [Nm].

[0080] In the first and second embodiments, the control command was a notch command that commands with the value of a notch (number of notches), but in the third embodiment, the control command is a torque command that commands with the value of torque.

[0081] The induction motor system 1000c in this third embodiment includes, for example, as shown in FIG. 14, a position velocity FB control unit PVC, a model-based FF control unit FFC, an adder SM, a torque forward-reverse control unit TRC, a hold unit HL, a duty ratio control unit DTCc, an induction motor unit IMU, and a position velocity sensor PVS, and drives a mechanical system MS such as an overhead traveling crane or a pump. Note that the induction motor unit IMU of the third embodiment includes a secondary resistance unit RN, but in the induction motor unit IMU shown in FIG. 14, this secondary resistance unit RN is omitted for illustration purposes.

[0082] In the induction motor system 1000c of the third embodiment, the induction motor unit IMU and the position velocity sensor PVS are the same as those in the induction motor system 1000a of the first embodiment, respectively, and thus their descriptions are omitted. The position velocity FB control unit PVC in the induction motor system 1000c of the third embodiment is the same as the position velocity FB control unit PVC in the induction motor system 1000a of the first embodiment, except that it outputs a torque command without converting the torque command into a notch command, and thus its description is omitted.

[0083] The hold unit HL in the induction motor system 1000c of the third embodiment is the same as the hold unit HL in the induction motor system 1000b of the second embodiment, except that it holds the switching command (switching control signal) from the torque forward / reverse control unit TRC, and thus its description is omitted.

[0084] The model-based FF control unit FFC is a feedforward control device (circuit) that generates a control command (torque command) obtained by a model of a mechanical system MS (for example, a dynamic characteristic model of an overhead traveling crane, etc.) prepared in advance based on a position velocity command (target position, target angular velocity) input from, for example, a host system or an input device, etc., and outputs the generated control command to the adder SM. In the third embodiment, the control command is a torque command as an example. The control command (torque command) includes the rotation direction of the induction motor IM. For example, the rotation direction is represented by the sign in the command value of the torque command. When the command value of the torque command is positive, it means forward rotation, and when the command value of the torque command is negative, it means reverse rotation.

[0085] The adder SM is a device (circuit) that adds the command value of the torque command from the model-based FF control unit FFC and the command value of the torque command from the position velocity FB control unit PVC to generate a torque command with the addition result as the command value, and outputs the generated torque command to the torque forward / reverse control unit TRC and the duty ratio control unit DTCc, respectively.

[0086] The torque forward / reverse control unit TRC is a device (circuit) that generates a switching command based on a control command (torque command) from the adder SM and outputs the generated switching command to the forward / reverse switch unit RS. More specifically, the torque forward / reverse control unit TRC stores the current connection state in the forward / reverse switch unit RS in a storage unit (not shown) of the induction motor system 1000b, and when the rotation direction according to the stored current connection state is different from the rotation direction according to the control command (torque command) from the adder SM, it generates a switching command to switch to the connection state corresponding to the rotation direction according to the control command (torque command) from the adder SM, and outputs the generated switching command to the forward / reverse switch unit RS. For example, when the rotation direction according to the stored current connection state is forward rotation and the rotation direction according to the control command (torque command) from the adder SM is reverse rotation, the torque forward / reverse control unit TRC generates a switching command to switch to the reverse connection state and outputs the generated switching command to the forward / reverse switch unit RS. On the other hand, when the rotation direction according to the stored current connection state is forward rotation and the rotation direction according to the control command (torque command) from the adder SM is forward rotation, the torque forward / reverse control unit TRC does not generate or output a switching command.

[0087] The duty ratio control unit DTCc is a device (circuit) that compares the switching time for switching whether a plurality of resistance elements in the secondary resistance unit RN are effective as the resistance elements of the secondary resistance unit RN with the maximum value of the real part of the eigenvalue of the induction motor IM, and controls the resistance value of the secondary resistance unit RN as follows according to the comparison result. The duty ratio control unit DTCc is connected to each control terminal of each first electronic switch element in the switch unit SW and outputs an on / off control signal for controlling the resistance value of the secondary resistance unit RN to each control terminal of each first electronic switch element in the switch unit SW. The maximum value of the real part of the eigenvalue of the induction motor IM corresponds to the time constant of the step response of the output torque in the induction motor IM.

[0088] First, when the switching time ΔT is smaller than the maximum value Amax, the duty ratio control unit DTCc selects, as the second A and second B resistance elements, from among a plurality of resistance elements in the secondary resistance unit RN, resistance values Rd corresponding to the command value (torque value τd) of the torque command, and obtains the second A coefficient DBn and the second B coefficient DBm such that the sum DBn×Rn + DBm×Rm of the second A multiplication result DBn×Rn obtained by multiplying the second A coefficient DBn by the second A resistance value Rn of the second A resistance element and the second B multiplication result DBm×Rm obtained by multiplying the second B coefficient DBm by the second B resistance value Rm of the second B resistance element becomes the resistance value Rd (=DBn×Rn + DBm×Rm) corresponding to the command value τ of the torque command (DBn = (Rm - Rd) / (Rm - Rn) = 1 - DBm, DBm = (Rd - Rn) / (Rm - Rn) = 1 - DBn, provided that Rn < Rm). Then, the on / off of the first electronic switch element is controlled so that, among the plurality of resistance elements, the second A resistance element is made effective as the resistance element of the secondary resistance unit RN, thereby obtaining the second A on-time Tn, and the on / off of the first electronic switch element is controlled so that, among the plurality of resistance elements, the second B resistance element is made effective as the resistance element of the secondary resistance unit RN, thereby obtaining the second B on-time Tm. The resistance value of the secondary resistance unit RN is controlled by controlling the on / off of the first electronic switch element such that the second duty ratio DBn:DBm (=Tn:Tm) is the ratio of the obtained second A coefficient DBn to the second B coefficient DBm.

[0089] The state equations of the induction motor IM are generally given by the following equations 1a to 1e, and the real part of the eigenvalue is the real part of the eigenvalue in the matrix A given by equation 1c.

[0090]

Equation

[0091] Here, ẋ is the differential value of the state vector x. In Equation 1a, a dot is placed above x, but for the sake of description, the dot is described following "x". The state vector x and the output vector y are such that when the induction motor IM is represented in the γ-δ coordinate system with the stator currents being iγs and iδs and the rotor currents being iγr and iδr, x = y = the vertical vector [iγs, iδs, iγr, iδr], V is the primary side power supply voltage in the γ-δ coordinate system, ω is the primary side power supply angular velocity, ωs is the slip angular velocity (ωs = ω - ωe, ωe; electrical angular velocity), Ls is the stator inductance in the γ-δ coordinate system, Lr is the rotor inductance in the γ-δ coordinate system, and M is the mutual inductance in the γ-δ coordinate system.

[0092] The resistance value Rd corresponding to the command value τ of the torque command is generally given by the following Equations 2a to 2d.

[0093]

Equation

[0094] Therefore, the duty ratio control unit DTCc first obtains the resistance value Rd corresponding to the command value τd of the torque command by using Equations 2a to 2d, and selects the second A and second B resistance elements from among the plurality of resistance elements in the secondary resistance unit RN so as to sandwich the obtained resistance value Rd. Among the plurality of resistance elements in the secondary resistance unit RN, the resistance elements that are effective as the resistance elements of the secondary resistance unit RN are indicated by the number of notches, so the second A and second B resistance elements can be represented by the number of notches. Assuming that the second A resistance element having the second A resistance value Rn is n notches and the second B resistance element having the second B resistance value Rm is m notches, the duty ratio control unit DTCc will select n notches and m notches by the above selection. For example, in the example shown in FIG. 2, the fourth resistance value R4 of 4 notches < the third resistance value R3 of 3 notches < the second resistance value R2 of 2 notches < the first resistance value R1 of 1 notch, and assuming that the resistance value Rd corresponding to the command value τ of the torque command is a value between the third resistance value R3 and the second resistance value R2, the duty ratio control unit DTCc will select, for example, 3 notches and 2 notches by the above selection. Alternatively, for example, the duty ratio control unit DTCc may select 4 notches and 2 notches, or for example, may select 3 notches and 1 notch, or for example, may select 4 notches and 1 notch. When there are a plurality of selectable combinations, any of the plurality of selectable combinations may be selected. Since there will be reciprocation between the second A resistance element Rn of n notches and the second B resistance element Rm of m notches at the second duty ratio DBn:DBm, it is preferable that the variation in the resistance value is small, so it is preferable to select a combination in which the number of notches is continuous. In other words, it is preferable that the duty ratio control unit DTCc selects the second A and second B resistance elements so that there is no resistance value of other resistance elements between the second A resistance value Rn of the second A resistance element and the second B resistance value Rm of the second B resistance element.

[0095] Subsequently, the duty ratio control unit DTCc obtains the second A and second B coefficients DBn and DBm according to DBn = (Rm - Rd) / (Rm - Rn) = 1 - DBm and DBm = (Rd - Rn) / (Rm - Rn) = 1 - DBn, and obtains the second duty ratio DBn:DBm.

[0096] Then, among the plurality of resistance elements in the secondary resistance unit RN, the duty ratio control unit DTCc controls the on / off of the first electronic switch element so that the first resistance element is valid as the resistance element of the secondary resistance unit RN, thereby obtaining the second A on-time Tn. And among the plurality of resistance elements, the duty ratio control unit DTCc controls the on / off of the first electronic switch element so that the second resistance element is valid as the resistance element of the secondary resistance unit RN, thereby obtaining the second B on-time Tm. The duty ratio control unit DTCc controls the on / off of the first electronic switch element so that the second duty ratio DBn:DBm (= Tn:Tm), which is the ratio of the obtained second A coefficient DBn to the second B coefficient DBm, is achieved, thereby controlling the resistance value of the secondary resistance unit RN. In other words, the duty ratio control unit DTCc controls the on / off of the first electronic switch element in the secondary resistance unit RN so that the second A on-time Tn with the secondary resistance unit RN having n notches and the second B on-time Tm with the secondary resistance unit RN having m notches satisfy the second duty ratio DBn:DBm (= Tn:Tm). In the example shown in FIG. 2, the duty ratio control unit DTCc controls the on / off of the first electronic switch elements Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c of each switch unit SW1~SW3 corresponding to each stage RN1~RN3 in the secondary resistance unit RN so that DBn:DBm = Tn:Tm. Thereby, the secondary resistance unit RN is controlled so that the resistance value of the secondary resistance unit RN becomes the resistance value Rd corresponding to the command value τd of the torque command. Since the second duty ratio DBn:DBm can be continuously changed, the resistance value Rd can be continuously changed, so the command value τ of the torque command can also be continuously specified, and the output torque of the induction motor IM can be continuously changed.

[0097] Note that the electrical angular velocity ωe (= (mechanical angular velocity) × (number of poles)) corresponding to the angular velocity (mechanical angular velocity) measured by the position velocity sensor PVS is obtained, and two notches are selected so that the output torque of the target torque is obtained at this electrical angular velocity ωe. In the control based on the second duty ratio, the switch unit SW is controlled at the second duty ratio.

[0098] For example, when the current electrical angular velocity ωe is 150 [rad / s] and the command value τd of the torque command is 200 [Nm], from Equation 1a, there are usually two resistance values Rd corresponding to the command value τd. In FIG. 15, the speed-torque characteristics β1 and β2 corresponding to these two resistance values -Rd and +Rd are shown. Here, among the two resistance values Rd, the smaller resistance value is -Rd, and its speed-torque characteristic is β1. Among the two resistance values Rd, the larger resistance value is +Rd, and its speed-torque characteristic is β2. In this case, for example, n = 4, m = 3 or 2 or 1 is selected. Generally, in the vicinity of the command value τ of the torque command, since the smaller resistance value -Rd has a negative slope and the larger resistance value +Rd has a positive slope, it is preferable to select the smaller resistance value -Rd having a negative slope for stable control.

[0099] Also, for example, when the current electrical angular velocity ωe is 150 [rad / s] and the command value τd of the torque command is 155 [Nm], the speed-torque characteristics β1 and β2 corresponding to the two resistance values -Rd and +Rd are shown in FIG. 16. In the example shown in FIG. 16, since the fourth resistance value R4 of the 4 notches < the smaller resistance value Rd- < the third resistance value R3 of the 3 notches < the larger resistance value Rd+ < the second resistance value R2 of the 2 notches < the first resistance value R1 of the 1 notch, the combinations of the notch numbers of the first and second resistance elements that become the larger resistance value Rd+ are the combination of 1 notch and 3 notches, the combination of 2 notches and 3 notches, and the combination of 2 notches and 4 notches. Since the travel between the two n notches and m notches is performed at the second duty ratio DBn:DBm, it is preferable that the variation in the resistance value is smaller. In this case, the combination of 2 notches and 3 notches is preferable.

[0100] On the other hand, from Equation 2a, the resistance value Rd corresponding to the command value τd of the torque command may have a double root. The resistance value Rd in the case of this double root is given by the following Equation 3 and becomes the maximum torque that can be output at the current slip angular velocity ωs (= ω - ωe). The second duty ratios DBn:DBm in this case are given by DBn = (Rm - Rd) / (Rm - Rn) and DBm = (Rd - Rn) / (Rm - Rn), similar to the above. The speed-torque characteristics in this case are shown in FIG. 17.

[0101]

Equation

[0102] During the stop with the electrical angular velocity ωe = 0 [rad / s], the step responses of the output torque when the notch is step-changed are illustrated in FIGS. 18 to 20. For example, when changing stepwise from 1 notch to 1.5 notches as shown in FIG. 18A, the secondary resistance section RN moves back and forth between 1 notch and 2 notches with a second duty ratio of 0.5:0.5. As can be seen from FIGS. 18 to 20, the output torque has a very fast step response in about 1 [ms] to 2 [ms], and good torque characteristics are obtained. On the other hand, in the movement to and from a notch with a large number of notches, a transient response around the commercial frequency 60 [Hz] of the primary power supply Vcc can be seen in the step response. Therefore, it is preferable that the mechanical system MS of the induction motor system 1000c is a device that is insensitive to this transient response. For example, it is preferable that the natural frequencies of the induction motor IM and the mechanical system MS are 10 [Hz] or less.

[0103] As can be seen from the state equations shown in Formula 1a to Formula 1e, since the slip angular velocity ωs is included in the formula, the response of the output torque also changes depending on the rotational speed of the induction motor IM. As an example, when the electrical angular velocity ωe is 150 [rad / s] and a step change is made from 3 notches to 3.5 notches during rotation, the step response of the output torque is illustrated in FIG. 21. The step response of the output torque during rotation shown in this FIG. 21 has a reduced transient response around 60 [Hz] as described above compared to the step response of the output torque during stop shown in FIGS. 18 to 20, which is preferable. It can be seen that the time constant in the output torque and the step response of the output torque varies depending on the speed range.

[0104] On the other hand, when the switching time ΔT is equal to or greater than the maximum value Amax, the duty ratio control unit DTCc selects the third A and third B resistance elements from among a plurality of resistance elements in the secondary resistance unit RN so that the command value τd of the torque command is sandwiched between the third A output torque τn(ωe) at the third A resistance element and the third B output torque τm(ωe) at the third B resistance element, and the sum DCn×τn(ωe)+DCm×τm(ωe) of the third A multiplication result DCn×τn(ωe) obtained by multiplying the third A coefficient DCn by the third A output torque τn(ωe) and the third B multiplication result DCm×τm(ωe) obtained by multiplying the third B coefficient DCm by the third B output torque τm(ωe) is equal to the command value τd of the torque command (=DCn×τn(ωe)+DCm×τm(ωe)). The third A and third B coefficients DCn and DCm (DCn=(τm(ωe)-τd) / (τm(ωe)-τn(ωe))=1-DCm, DCm=(τd-τn(ωe)) / (τm(ωe)-τn(ωe))=1-DCn, provided that τn(ωe)<τm(ωe)) are obtained, and the on / off of the first electronic switch element is controlled so that the third A resistance element among the plurality of resistance elements is made effective as the resistance element of the secondary resistance unit RN, thereby obtaining the third A on-time Tn, and the on / off of the first electronic switch element is controlled so that the third B resistance element among the plurality of resistance elements is made effective as the resistance element of the secondary resistance unit, thereby obtaining the third B on-time Tm. The resistance value of the secondary resistance unit RN is controlled by controlling the on / off of the first electronic switch element so that the third duty ratio DCn:DCm (=Tn:Tm) is the ratio of the obtained third A coefficient DCn to the third B coefficient DCm.

[0105] More specifically, the duty ratio control unit DTCc first selects the 3A and 3B resistance elements from among the plurality of resistance elements in the secondary resistance unit RN such that the command value τd of the torque command is sandwiched between the 3A output torque τn(ωe) at the 3A resistance element and the 3B output torque τm(ωe) at the 3B resistance element. In other words, if the 3A resistance element that results in the 3A output torque τn(ωe) is the n-th notch and the 3B resistance element that results in the 3B output torque τm(ωe) is the m-th notch, the duty ratio control unit DTCc will select the n-th notch and the m-th notch by the above selection. When there are a plurality of selectable combinations, any of the plurality of selectable combinations may be selected, but since it is preferable that the fluctuation of the resistance value is small because the 3A and 3B duty ratios DCn:DCm will go back and forth between the n-th notch 3A resistance element and the m-th notch 3B resistance element, it is preferable to select a combination in which the number of notches is continuous.

[0106] Subsequently, the duty ratio control unit DTCc obtains the 3A and 3B coefficients DCn, DCm according to DCn = (τm(ωe) - τd) / (τm(ωe) - τn(ωe)) = 1 - DCm, DCm = (τd - τn(ωe)) / (τm(ωe) - τn(ωe)) = 1 - DCn, and obtains the 3B duty ratio DCn:DCm.

[0107] Then, the duty ratio control unit DTCc controls the on / off of the first electronic switch element so that, among the plurality of resistance elements in the secondary resistance unit RN, the third A resistance element is made effective as the resistance element of the secondary resistance unit RN, and the third A on-time Tn is obtained. Also, among the plurality of resistance elements, the third B resistance element is made effective as the resistance element of the secondary resistance unit RN, and the third B on-time Tm is obtained by controlling the on / off of the first electronic switch element. The duty ratio control unit DTCc controls the on / off of the first electronic switch element so that the third duty ratio DCn:DCm (= Tn:Tm), which is the ratio of the obtained third A coefficient DCn and third B coefficient DCm, is achieved, thereby controlling the resistance value of the secondary resistance unit RN. In other words, the duty ratio control unit DTCc controls the on / off of the first electronic switch element in the secondary resistance unit RN so that the third A on-time Tn with the secondary resistance unit RN having n notches and the third B on-time Tm with the secondary resistance unit RN having m notches result in the third duty ratio DCn:DCm (= Tn:Tm). In the example shown in FIG. 2, the duty ratio control unit DTCc controls the on / off of each first electronic switch element Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c of each switch unit SW1~SW3 corresponding to each stage RN1~RN3 in the secondary resistance unit RN so that DCn:DCm = Tn:Tm. As a result, the secondary resistance unit RN is controlled so that the resistance value of the secondary resistance unit RN becomes the command value τd of the torque command. Since the third duty ratio DCn:DCm can be continuously changed, the command value τd of the torque command can also be continuously specified, and the output torque of the induction motor IM can be continuously changed.

[0108] Note that the electrical angular velocity ωe (= (mechanical angular velocity) × (number of poles)) corresponding to the angular velocity (mechanical angular velocity) measured by the position velocity sensor PVS is obtained, and two notches are selected so that the output torque of the target torque can be obtained at this electrical angular velocity ωe. In the control based on the third duty ratio, the switch unit SW is controlled by the third duty ratio.

[0109] For example, when the current electrical angular velocity ωe is 150 [rad / s] and the command value τd of the torque command is 155 [Nm], the speed-torque characteristics when the secondary resistance section RN is controlled with a third duty ratio DCn:DCm between the 3rd notch and the 4th notch are shown in Fig. 22, and the speed-torque characteristics when the secondary resistance section RN is controlled with a third duty ratio DCn:DCm between the 2nd notch and the 3rd notch are shown in Fig. 23, and the speed-torque characteristics when the secondary resistance section RN is controlled with a third duty ratio DCn:DCm between the 1st notch and the 3rd notch are shown in Fig. 24. When there are multiple combinations of notches, it is preferable that the variation in the resistance value is small, so it is preferable to select a combination in which the notch numbers are consecutive. In other words, the duty ratio control unit DTCc preferably selects the 3A and 3B resistance elements so that there is no resistance value of other resistance elements between the 3A resistance value of the 3A resistance element and the 3B resistance value of the 3B resistance element. In the examples shown in Figs. 22 to 24, the speed-torque characteristics of the 4th notch have a positive slope that results in unstable control in the region of 320 [rad / s] or less, so a combination of notches that does not include the 4th notch is preferable. From these, in the examples shown in Figs. 22 to 24, a combination of the 2nd notch and the 3rd notch is preferable.

[0110] Note that the switching time ΔT is stored in the induction motor system 1000c in advance. The duty ratio control unit DTCc obtains the maximum value Amax of the real part of the eigenvalue of the induction motor IM from Equation 1c, compares the switching time ΔT with the maximum value Amax, and selects either the control method based on the above-described second duty ratio Dn:Dm or the control method based on the third duty ratio Dn:Dm according to the result of the comparison. However, due to the design of the induction motor system 1000c or the completion of the actual machine of the induction motor system 1000c, the switching time ΔT can be measured or estimated from the specifications (switching time) of the first electronic switch element, and the maximum value Amax of the real part of the eigenvalue of the induction motor IM can be obtained from Equation 1c. Therefore, the switching time ΔT and the maximum value Amax are compared in advance, and either one of the control method based on the above-described second duty ratio Dn:Dm and the control method based on the third duty ratio Dn:Dm is selected according to the result of the comparison, and a duty ratio control unit DTCc incorporating the selected control method may be created (mounted on the actual machine).

[0111] Note that the duty ratio control unit DTCc corresponds to another example of a secondary resistance control unit that controls the resistance value of the secondary resistance unit by controlling the on / off of the first electronic switch element based on a predetermined control command.

[0112] As described above, the induction motor system 1000c in the third embodiment and the induction motor control device provided therein include first electronic switch elements Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c for switching whether or not the plurality of resistance elements RN1a, RN1b, RN1c; RN2a, RN2b, RN2c; RN3a, RN3b, RN3c in the secondary resistance unit RN are effective as the resistance elements of the secondary resistance unit RN. Therefore, the resistance value of the secondary resistance unit RN can be controlled by controlling the on / off of the first electronic switch elements Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c based on a predetermined control command (here, a torque command), and thus, the induction motor IM can be automatically controlled.

[0113] The above-described induction motor system 1000c and the induction motor control device control the on / off of the first electronic switch elements Tr1a to Tr1c, Tr2a to Tr2c, and Tr3a to Tr3c with a second duty ratio DBn:DBm based on the resistance value Rd corresponding to the command value τd of the torque command, thereby controlling the resistance value of the secondary resistance section RN. Therefore, the induction motor IM can be automatically controlled over the entire outputtable torque range of the induction motor IM. Since the above-described induction motor system 1000c and the induction motor control device can continuously change the second duty ratio DBn:DBm, the output torque can be continuously changed to automatically control the induction motor IM.

[0114] The above-described induction motor system 1000c and the induction motor control device control the on / off of the first electronic switch elements Tr1a to Tr1c, Tr2a to Tr2c, and Tr3a to Tr3c with a third duty ratio DCn:DCm based on the command value τd of the torque command, thereby controlling the resistance value of the secondary resistance section RN. Therefore, the induction motor IM can be automatically controlled over the entire outputtable torque range of the induction motor IM. Since the above-described induction motor system 1000c and the induction motor control device can continuously change the third duty ratio DCn:DCm, the output torque can be continuously changed to automatically control the induction motor IM.

[0115] In addition, in the above-described first to third embodiments, the induction motor systems 1000a to 1000c and their induction motor control devices may further include a second electronic switch element for opening or short-circuiting the phases of the secondary winding, and an insulation state forming section for opening the phases of the secondary winding by turning off the second electronic switch element to bring the phases of the secondary winding into an insulated state (first modified form).

[0116] FIG. 25 is a circuit diagram mainly of an induction motor and a secondary resistance section and a switch section in an induction motor control device in the induction motor system of the first modified form. FIG. 26 is a diagram for explaining the line voltage between the secondary sides (the line voltage between the U phase and the V phase) in the induction motor system of the first modified form. FIG. 26A shows the case where a thyristor is used for the second electronic switch element, and FIG. 26B shows the case where a transistor is used for the second electronic switch element. The horizontal axis of each figure is time (elapsed time) [s], and the vertical axis of each of these is the line voltage of the secondary winding [V]. FIG. 27 is a graph for showing, as an example, the torque speed characteristics in the case of controlling with a third duty ratio based on the command value of the torque command between 0 notch and 1 notch in the induction motor system of the first modified form. In FIG. 27, the horizontal axis is the electrical angular velocity [rad / s], and the vertical axis is the torque [Nm].

[0117] The secondary resistance part RN shown in FIG. 2 above is connected to the other ends of the first 11th resistor element RN1a, the 21st resistor element RN2a, and the 31st resistor element RN3a connected in series, the other ends of the first 12th resistor element RN1b, the 22nd resistor element RN2b, and the 32nd resistor element RN3b connected in series, and the one ends of the first 13th resistor element RN1c, the 23rd resistor element RN2c, and the 33rd resistor element RN3c connected in series. They are connected to each other. However, in this first deformation mode, as shown in FIG. 25, the other ends of the first 11th resistor element RN1a, the 21st resistor element RN2a, and the 31st resistor element RN3a connected in series and the other ends of the first 12th resistor element RN1b, the 22nd resistor element RN2b, and the 32nd resistor element RN3b connected in series are connected via the first thyristor SCRa of the second electronic switch element. The other ends of the first 12th resistor element RN1b, the 22nd resistor element RN2b, and the 32nd resistor element RN3b connected in series and the one ends of the first 13th resistor element RN1c, the 23rd resistor element RN2c, and the 33rd resistor element RN3c connected in series are connected via the second thyristor SCRb of the second electronic switch element. The one ends of the first 13th resistor element RN1c, the 23rd resistor element RN2c, and the 33rd resistor element RN3c connected in series and the other ends of the first 11th resistor element RN1a, the 21st resistor element RN2a, and the 31st resistor element RN3a connected in series are connected via the third thyristor SCRc of the second electronic switch element. Then, all of the first electronic switch elements Tr1a~Tr1c; Tr2a~Tr2c; Tr3a~Tr3c in the switch part SW are turned off, and the first to third thyristors of the second electronic switch element are turned off. As a result, the phases of the secondary winding are opened and the phases of the secondary winding are in an insulated state. Each control terminal for turning on and off in these first to third thyristors SCRa~SCRc receives, for example, from the rounding processing part RP in the first embodiment, from the duty ratio control part DTCb in the second embodiment, and from the duty ratio control part DTCb in the third embodiment, each on-off control signal, and each on-off is controlled. This insulated state becomes the 0 notch where the resistance value of the secondary resistance part RN becomes infinite, and the 0 notch can be realized on the secondary side.As an example, these first to third thyristors SCRa to SCRc constitute an insulation state forming section SWa.

[0118] Instead of the first to third thyristors SCRa to SCRc, a transistor having a surge current withstand may be used as the second electronic switching element. However, when a transistor is used as the second electronic switching element, as shown in FIG. 26B, noise is generated in the line voltage of the secondary winding due to the surge current. On the other hand, when a thyristor is used as the second electronic switching element, as shown in FIG. 26A, the surge current can be suppressed and the noise can be reduced.

[0119] Such an induction motor system and an induction motor control device in the first modified form further include first to third thyristors SCRa to SCRc as an example of the insulation state forming section. Therefore, a 0 notch can be realized on the secondary side, low torque can be output in the low speed region, and controllability can be improved in the low speed region.

[0120] The induction motor system and the induction motor control device can suppress the surge voltage (current) that may occur when the phases of the secondary winding are opened and the phases of the secondary winding are insulated by using the first to third thyristors SCRa to SCRc as the second electronic switching element, and can reduce noise.

[0121] Further, in the configuration including this 0 notch, when the switch section SW is controlled by the second duty ratio based on the resistance value Rd corresponding to the command value τd of the torque command, and when the 0 notch and other notches are used, no matter what the second duty ratio (any second duty ratio) is, the resistance value of the secondary resistance section RN becomes infinite. Therefore, when the 0 notch and other notches are used, the duty ratio control section DTCc controls the switch section SW by the third duty ratio based on the command value τd of the torque command. FIG. 27 shows, as an example, the torque speed characteristics in the case of controlling by the third duty ratio based on the command value of the torque command between the 0 notch and the 1 notch.

[0122] Also, in the above-described first to third embodiments and their first modified forms, a thyristor may also be used for the first electronic switch element of the switch unit SW (second modified form). FIG. 28 is a circuit diagram mainly of the induction motor and the secondary resistance unit and the switch unit in the induction motor control device in the case of delta connection in the induction motor system of the second modified form. FIG. 29 is a circuit diagram mainly of the induction motor and the secondary resistance unit and the switch unit in the induction motor control device in the case of star connection in the induction motor system of the second modified form. As an example, FIG. 28 shows an example in which a thyristor is used for the first electronic switch element of the switch unit SW in the circuit shown in FIG. 25. In the above description, a so-called delta connection has been used, but a so-called star connection may also be used. As an example, FIG. 29 shows an example in which a star connection is used in the circuit shown in FIG. 28. By using a star connection, the withstand voltage can be improved.

[0123] In the induction motor system and the induction motor control device in such a second modified form, by using a thyristor for the first electronic switch element, the surge voltage (current) can be further suppressed and the noise can be reduced.

[0124] Also, in the above-described third embodiment, its first modified form and its second modified form, when a thyristor is used, the duty ratio control unit DTCc, which is an example of the secondary resistance control unit, sets the on-off period of each thyristor of the first and second electronic switch elements to any value in the range of 3 [Hz] or more and 10 [Hz] or less in terms of frequency, or sets the on-off period of each thyristor of the first and second electronic switch elements to a value that is an odd multiple of half the period of the primary side power supply frequency that supplies power to the primary winding (third modified form).

[0125] FIG. 30 is a diagram for explaining the U-phase current and the output torque in the induction motor system of the third modified form as an example when the switching period is 6 [Hz]. FIG. 31 is a diagram for explaining the U-phase current and the output torque in the induction motor system of the third modified form as a comparative example when the switching period is 60 [Hz]. FIGS. 30A and 31A show the time change of the output torque, the horizontal axis thereof is time (elapsed time) [s], and the vertical axis thereof is torque [Nm]. FIGS. 30B and 31B show the time change of the U-phase current, the horizontal axis thereof is time (elapsed time) [s], and the vertical axis thereof is the U-phase current [A].

[0126] Since the zero crossing at which the current value becomes 0 is the off-timing for the thyristor, when the switch unit SW is controlled with the second and third duty ratios, the thyristor does not turn off until the zero crossing. That is, a time lag may occur between the off-timing in the on-off control signal and the actual off-timing. Since the secondary-side current frequency is twice the primary-side power supply frequency (for example, commercial frequency 60 [HZ] or 50 [Hz]), the on-off switching period is set to a period slower than the period corresponding to the frequency twice the primary-side power supply frequency (for example, 120 (= commercial frequency 60 × 2) [HZ] or 100 (= commercial frequency 50 × 2 [Hz])).

[0127] On the other hand, for example, when the switching period is set to the period of the frequency 60 [Hz], an offset component occurs in each phase current (an example of the U-phase current is shown in FIG. 31B), and as shown in FIG. 31A for example, the output torque may deviate (shift) from the target torque.

[0128] Therefore, for example, when using thyristors, the duty ratio control unit DTCc sets the on-off cycle of each thyristor of the first and second electronic switch elements to any value within the range of 3 [Hz] or more and 10 [Hz] or less in terms of frequency. Alternatively, for example, when using thyristors, the duty ratio control unit DTCc sets the on-off cycle of each thyristor of the first and second electronic switch elements to a value that is an odd multiple of the half-cycle of the primary side power supply frequency that supplies power to the primary winding.

[0129] In the former case, for example, when the mechanical system is an overhead traveling crane, if the rope length is 1 [m], its natural frequency is about 1.5 [Hz]. Therefore, the switching period is set to a period corresponding to a frequency of 3 to 5 [Hz] or more, which is 2 to 3 times that value. In addition, the torque offset in Fig. 31A is due to the offset voltage caused by the off-timing of each phase being shifted by about half the cycle of the primary side power supply frequency. If the switching period is not set to an odd multiple of that value, the shorter the switching period, the larger the offset voltage, and it will be greatly affected. Therefore, it is necessary to make the switching period 10 times or more longer than the half-cycle, and 10 to 12 [HZ] (12 [HZ] for commercial frequency 60 [HZ], 10 [HZ] for 50 [Hz]) or less. That is, the switching period needs to be 3 to 5 [HZ] or more and 10 to 12 [HZ] or less. For example, if it is set to 6 [Hz], the example shown in Fig. 31 is improved as shown in Fig. 30. The offset component in each phase current is suppressed, and the output torque stabilizes with its average value falling to 0 and is improved.

[0130] In the latter case, since the offset component in each phase current significantly occurs by switching at an even multiple of the half-wave period, by making it an odd multiple, the offset components generated for each switching period are inverted. As a result, they cancel each other out alternately, and the offset component in each phase current is suppressed. For example, when the primary side power supply frequency is 60 [Hz], the half-cycle is 8.333 [ms]. Therefore, as the odd multiple of the half-wave period, 1 times 8.333 [ms], 3 times 25 [ms], 5 times 41.667 [ms], etc. are used.

[0131] In such a third modified form, the induction motor system and the induction motor control device can suppress the offset of each phase current and can suppress the deviation between the command value of the torque command and the output torque.

[0132] Also, in these above-described third embodiment, its first modified form, its second modified form, and its third modified form, when using a thyristor, the duty ratio control unit DTCc, which is an example of the secondary resistance control unit, may shorten the on-time in each thyristor of the first and second electronic switch elements by a predetermined time (for example, 30 [degrees] or 45 [degrees] in phase with respect to the power supply frequency on the primary side) set in advance from the target on-time (fourth modified form).

[0133] FIG. 32 is a diagram for explaining the on-time in the induction motor system of the fourth modified form. FIG. 32A shows the phase current, where the horizontal axis is the phase [degrees] and the vertical axis is the phase current, and the dashed line shows the virtual phase current. FIG. 32B shows the effective current, where the horizontal axis is the phase [degrees] and the vertical axis is the effective current, and the dashed line shows the virtual phase.

[0134] When using a thyristor, as described above, since the turn-off timing of the thyristor lags behind the turn-off timing in the on-off control signal, the on-time of the thyristor can be longer than the on-time (target on-time) in the on-off control signal. As a result, the actual duty ratio can deviate from the duty ratio (target duty ratio) in the on-off control signal. This is illustrated in Fig. 32. In Fig. 32, if the timing when one phase of the phase current is turned off by the thyristor is set as phase 0 degrees, in order for one phase to be turned off at 0 degrees, the off command from the upper system needs to come at a timing of phase -60 to 0 [degrees]. Now, when the switching period is not an integer multiple of half the power frequency, the expected value of the delay from the off command from the upper system until one phase is actually turned off is -30 [degrees], which is the average value of -60 to 0 [degrees]. On the other hand, when the switching period is an integer multiple of half the power frequency, the turn-off timing from the upper system always has a constant phase. Here, by detecting each phase current on the secondary side, it is possible to synchronize with 0 [degrees] and make the phase shift of the turn-off timing 0 [degrees].

[0135] Next, focusing on the behavior after one phase is turned off, its effective current gradually decreases after one phase is turned off and becomes 0 at phase 90 [degrees]. From Fig. 32, the expected value from 0 [degrees] until the effective current becomes 0 is equivalent to 45 degrees in the state where three phases are energized. From the above, when the switching period is an integer multiple of half a wave and is synchronized with phase 0 [degrees], it is 45 [degrees]. When not synchronized and the turn-off timing cannot be measured at phase 0 [degrees], or when the switching period is not an integer multiple, the turn-off timing is expected to be delayed by 45 [degrees] + 30 [degrees]. Therefore, by shortening the on-time in advance by the amount of this delay, control can be achieved with a closer target duty ratio. Note that this phase 45 [degrees] is a value with respect to the power frequency on the primary side. In the case of 60 [Hz], it corresponds to (1 / 60)×(45 / 360) = 2.0833 [ms], and the phase 30 [degrees] corresponds to (1 / 60)×(30 / 360) = 1.3889 [ms].

[0136] In such a fourth modified form, the induction motor system and the induction motor control device can compensate for the delay of the off timing and improve the controllability by making it shorter than the target on-time based on the control command.

[0137] In order to represent the present invention, the present invention has been appropriately and sufficiently described through embodiments while referring to the drawings above. However, it should be recognized that those skilled in the art can easily make changes and / or improvements to the above-described embodiments. Therefore, as long as the modified forms or improved forms implemented by those skilled in the art do not depart from the scope of the claims described in the claims, such modified forms or such improved forms are construed to be included in the scope of the claims of the claims.

Explanation of Signs

[0138] 1000a, 1000b, 1000c Induction motor system PVC Position velocity FB control unit NRC Notch forward / reverse control unit RP Rounding processing unit IMU Induction motor unit PVS Position velocity sensor HL Hold unit TDCb, TDCc Duty ratio control unit FFC Model-based FF control unit SM Adder IM Induction motor RN Secondary resistance unit SW Switch unit RS Forward / reverse switch unit

Claims

1. An induction motor control device for controlling an induction motor having a primary winding and a secondary winding, a secondary resistance section including a plurality of resistance elements connected to each phase of the secondary winding and connected in series, a switch section including a first electronic switch element for switching whether or not each of the plurality of resistance elements is effective as a resistance element of the secondary resistance section, and a secondary resistance control section for controlling the resistance value of the secondary resistance section by controlling on / off of the first electronic switch element based on a predetermined control command. Induction motor control device.

2. The control command is a notch command representing the number of notches indicating the resistance elements effective as the resistance elements of the secondary resistance section among the plurality of resistance elements, and the secondary resistance control section rounds off the command value of the notch command to an integer, and controls the on / off of the first electronic switch element based on the rounded-off command value to control the resistance value of the secondary resistance section. The induction motor control device according to Claim 1.

3. The control command is a notch command representing the number of notches indicating the resistance elements effective as the resistance elements of the secondary resistance section among the plurality of resistance elements, The secondary resistance control unit obtains first A and first B integers so as to sandwich the command value of the notch command, and obtains the first A and first B coefficients such that the sum of a first A multiplication result obtained by multiplying the first A coefficient by the first A integer and a first B multiplication result obtained by multiplying the first B coefficient by the first B integer is equal to the command value of the notch command. Among the plurality of resistance elements, the first A on-time obtained by controlling the on / off of the first electronic switch element so that the first A resistance element corresponding to the first A integer is valid as the resistance element of the secondary resistance unit, and the first B on-time obtained by controlling the on / off of the first electronic switch element so that the first B resistance element corresponding to the first B integer among the plurality of resistance elements is valid as the resistance element of the secondary resistance unit, the resistance value of the secondary resistance unit is controlled by controlling the on / off of the first electronic switch element so that the ratio of the first A coefficient and the first B coefficient obtained is the first duty ratio. The induction motor control device according to claim 1.

4. The control command is a torque command, When the switching time for switching the effective or not is smaller than the maximum value of the real part of the eigenvalue of the induction motor, the secondary resistance control unit selects, as second A and second B resistance elements, from the plurality of resistance elements, so as to sandwich the resistance value corresponding to the command value of the torque command, and obtains the second A and second B coefficients such that the sum of a second A multiplication result obtained by multiplying the second A coefficient by the second A resistance value of the second A resistance element and a second B multiplication result obtained by multiplying the second B coefficient by the second B resistance value of the second B resistance element is equal to the resistance value corresponding to the command value of the torque command. Among the plurality of resistance elements, the second A on-time obtained by controlling the on / off of the first electronic switch element so that the second A resistance element is valid as the resistance element of the secondary resistance unit, and the second B on-time obtained by controlling the on / off of the first electronic switch element so that the second B resistance element among the plurality of resistance elements is valid as the resistance element of the secondary resistance unit, the resistance value of the secondary resistance unit is controlled by controlling the on / off of the first electronic switch element so that the ratio of the second A coefficient and the second B coefficient obtained is the second duty ratio. The induction motor control device according to claim 1.

5. The control command is a torque command, When the switching time for switching whether or not to be effective is equal to or greater than the maximum value of the real part of the eigenvalue of the induction motor, the secondary resistance control unit selects the third A and third B resistance elements from the plurality of resistance elements so that the command value of the torque command is sandwiched between the third A output torque of the third A resistance element and the third B output torque of the third B resistance element, obtains the third A and third B coefficients such that the sum of the third A multiplication result obtained by multiplying the third A coefficient by the third A output torque and the third B multiplication result obtained by multiplying the third B coefficient by the third B output torque becomes the command value of the torque command, and controls the on / off of the first electronic switch element so that the third A resistance element among the plurality of resistance elements is made effective as the resistance element of the secondary resistance unit to obtain a third A on-time, and controls the on / off of the first electronic switch element so that the third B resistance element among the plurality of resistance elements is made effective as the resistance element of the secondary resistance unit to obtain a third B on-time, and controls the on / off of the first electronic switch element so that the third A on-time and the third B on-time become a third duty ratio that is the ratio of the obtained third A coefficient and third B coefficient, thereby controlling the resistance value of the secondary resistance unit. The induction motor control device according to claim 1.

6. It includes a second electronic switch element for opening or short-circuiting the phases of the secondary winding, and further includes an insulation state forming unit that opens the phases of the secondary winding by turning off the second electronic switch element to put the phases of the secondary winding in an insulated state. The induction motor control device according to claim 1.

7. The second electronic switch element is a thyristor. The induction motor control device according to claim 6.

8. The first electronic switch element is a thyristor. The induction motor control device according to claim 7.

9. The induction motor is a three-phase induction motor, The secondary resistance control unit sets the on-off cycle of each thyristor of the first and second electronic switch elements to any value within a range of 3 [Hz] or more and 10 [Hz] or less in terms of frequency, or sets the on-off cycle of each thyristor of the first and second electronic switch elements to a value that is an odd multiple of half the primary-side power supply frequency that powers the primary winding. The induction motor control device according to claim 8.

10. The induction motor is a three-phase induction motor, The secondary resistance control unit makes the on-time of each thyristor of the first and second electronic switch elements shorter than the target on-time. The induction motor control device according to claim 8.

11. It includes a second electronic switch element for opening or short-circuiting the phases of the secondary winding, and further includes an insulation state forming unit that opens the phases of the secondary winding by turning off the second electronic switch element to put the phases of the secondary winding in an insulated state. The induction motor control device according to claim 5.

12. The induction motor is a three-phase induction motor having U-phase, V-phase, and W-phase, A forward-reverse switch unit that switches between a first connection state in which each of the U-phase and V-phase of the power supply is connected to each of the U-phase and V-phase in the primary winding of the induction motor, and a second connection state in which each of the U-phase and V-phase of the power supply is connected to each of the V-phase and U-phase in the primary winding of the induction motor, It further includes a hold unit that holds a switching command for switching the connection state of the forward-reverse switch unit for a time longer than the switching required time for switching the connection state in the forward-reverse switch unit. The switching command is input to the forward-reverse switch unit via the hold unit. The induction motor control device according to claim 1.

13. An induction motor including a primary winding and a secondary winding, and an induction motor control device for controlling the induction motor, the induction motor system comprising: The induction motor control device is the induction motor control device according to any one of claims 1 to 12, Induction motor system.

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