Pre-charging circuit and motor drive device

Abstract

A pre-charging circuit for pre-charging a smoothing capacitor connected to the DC output side of a rectifier for converting input AC power into DC power and outputting the DC power, the pre-charging circuit comprising: a switching unit having a switching element for switching the DC power; a switching element that electrically connects the three-phase AC power supply and the AC input side of the rectifier when turned on, and electrically disconnects the three-phase AC power supply and the AC input side of the rectifier when turned off; a power supply voltage detection circuit that detects the AC voltage of the three-phase AC power supply; and a control unit that controls the ON / OFF of the switching element of the switching unit on the basis of information relating to the AC voltage detected by the power supply voltage detection circuit.

Description

Technical Field

[0001] The present invention relates to a pre-charging circuit and a motor driving device. Background Art

[0002] In the motor drive device, the AC power input from the AC power source is converted into DC power by a rectifier (rectifier circuit) and output to the DC link, and the DC power in the DC link is converted into AC power by an inverter, and the AC power is supplied as the driving power of the motor. The DC link refers to the circuit part that electrically connects the DC output side of the rectifier (converter) with the DC input side of the inverter, and is sometimes also called "DC link part", "DC link", "DC link part", "DC bus" or "DC intermediate circuit".

[0003] A smoothing capacitor is provided in the DC link, and has the functions of suppressing the pulsation of the DC output of the rectifier and storing DC power. The smoothing capacitor needs to be pre-charged to a voltage of a predetermined magnitude from the time the power supply of the motor drive device is turned on to the time the motor drive starts (i.e., before the power conversion operation of the inverter starts). This charging is also called "preliminary charging" or "initial charging".

[0004] The preparatory charging starts from a state where no energy is stored in the smoothing capacitor. Therefore, after the power supply of the motor drive device is turned on, a large surge current flows from the AC power supply to the DC link via the rectifier. Therefore, a preparatory charging circuit is generally provided in the DC link, which performs preparatory charging of the smoothing capacitor while suppressing the surge current generated after the power supply of the motor drive device is turned on. The preparatory charging circuit is sometimes called an "initial charging circuit" or a "surge current suppression circuit".

[0005] Generally speaking, the pre-charging circuit is composed of a pre-charging resistor for suppressing inrush current and a switching element connected in parallel with the pre-charging resistor. During pre-charging, the switching element is kept in the off state (OFF), and the inrush current is suppressed by the pre-charging resistor. After the pre-charging is completed, the switching element is turned on, thereby bypassing the pre-charging resistor.

[0006] For example, a surge current prevention circuit for a DC power supply circuit is known, which has a rectifier circuit that is powered from an AC power supply via a semiconductor switching element and a smoothing capacitor connected to the output side of the rectifier circuit, and is characterized in that it has: a power supply voltage detection unit that detects the output voltage of the AC power supply; a terminal voltage detection unit that detects the terminal voltage of the smoothing capacitor during an off period of the semiconductor switching element; and a control unit that performs the following switching control: when the DC power supply circuit is started, at each time when the absolute value of the detection voltage of the power supply voltage detection unit decreases to a target level that is a predetermined level higher than the detection voltage of the terminal voltage detection unit after reaching a peak value, the semiconductor switching element is turned on, and the on state is maintained at least until a predetermined period set during the period when the absolute value of the detection voltage of the power supply voltage detection unit rises to the target level, and when the detection voltage of the terminal voltage detection unit rises to a predetermined voltage or more in response to the execution of the switching control, the control unit ends the switching control and maintains the semiconductor switching element in the on state (for example, refer to Patent Document 1).

[0007] For example, a power control device is known, characterized in that it comprises: a semiconductor element that performs a switching action to interrupt the AC output of an AC power supply; a control unit that performs switching control of the semiconductor element based on an input signal from the outside; an output current detection unit that detects the output current intermittently supplied to a load by the semiconductor element, and when the detection value of the output current detection unit exceeds a prescribed reference value, the control unit controls the semiconductor element in an active region so that the output current is lower than the reference value (for example, refer to patent document 2).

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2007-129875

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 09-212245 Summary of the invention

[0012] Problems to be solved by the invention

[0013] When an abnormality such as a short circuit occurs in a motor drive device, an overcurrent flows from the AC input side to the rectifier, which may damage the motor drive device. The present disclosure aims to protect the motor drive device from the overcurrent generated on the AC input side of the rectifier.

[0014] Means for solving problems

[0015] According to one embodiment of the present disclosure, a pre-charging circuit pre-charges a smoothing capacitor connected to a DC output side of a rectifier, wherein the rectifier converts input AC power into DC power and outputs the power, wherein the pre-charging circuit comprises: a switching unit having a switching element, which electrically connects a three-phase AC power supply to the AC input side of the rectifier when turned on, and electrically disconnects the three-phase AC power supply from the AC input side of the rectifier when turned off; a power supply voltage detection circuit, which detects an AC voltage of the three-phase AC power supply; and a control unit, which controls the switching element of the switching unit to be turned on and off based on information related to the AC voltage detected by the power supply voltage detection circuit.

[0016] According to one embodiment of the present disclosure, a motor drive device includes: a rectifier; a smoothing capacitor; the pre-charging circuit; and an inverter that converts DC power into AC power for driving the motor and outputs the converted AC power.

[0017] Effects of the Invention

[0018] According to one aspect of the present disclosure, it is possible to protect a motor drive device from an overcurrent generated on the AC input side of a rectifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a diagram showing a pre-charging circuit and a motor drive device according to the first embodiment of the present disclosure.

[0020] Figure 2 1 is a flowchart showing the operation flow of the pre-charging process performed by the pre-charging circuit according to the first embodiment of the present disclosure.

[0021] Figure 3 This is a flowchart showing the flow of operation of overcurrent protection processing performed by the motor drive device including the pre-charging circuit according to the first to third embodiments of the present disclosure.

[0022] Figure 4 1 is a waveform diagram showing a specific example of the operation of the switch section in the pre-charge process performed by the pre-charge circuit according to the first embodiment of the present disclosure.

[0023] Figure 5 It is a diagram showing a pre-charging circuit and a motor drive device according to a second embodiment of the present disclosure.

[0024] Figure 6 1 is a waveform diagram showing a specific example of the operation of the switch section in the pre-charge process performed by the pre-charge circuit according to the second embodiment of the present disclosure.

[0025] Figure 7 It is a diagram showing a pre-charging circuit and a motor drive device according to a third embodiment of the present disclosure.

[0026] Figure 8 : is a waveform diagram showing a specific example of the operation of the switch section in the pre-charge process performed by the pre-charge circuit according to the third embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] Hereinafter, the pre-charging circuit and the motor drive device according to the embodiment will be described with reference to the drawings. In the following description, the same reference numerals are given to the components having the same or similar functions, and the repeated description of these components may be omitted.

[0028] <First embodiment>

[0029] Figure 1 It is a diagram showing a pre-charging circuit and a motor drive device according to the first embodiment of the present disclosure.

[0030] In the first embodiment and the second and third embodiments described later, an example is shown in which the motor 6 is controlled by a motor drive device 100 connected to a three-phase AC power supply 5. If an example of a three-phase AC power supply 5 is listed, there are three-phase AC 400V power supply, three-phase AC 200V power supply, three-phase AC 600V power supply, etc. In addition, in each embodiment, the type of motor 6 is not particularly limited, for example, it can be an induction motor or a synchronous motor. In addition, the number of phases of the motor 6 is not particularly limited to each embodiment, for example, it can be three-phase or single-phase. Here, as an example, the motor 6 is set to three-phase. In addition, the number of motors 6 is not particularly limited to each embodiment, and it can also be multiple. Here, as an example, the motor 6 is set to one. Machines provided with the motor 6 include, for example, machine tools, robots, forging machines, injection molding machines, industrial machinery, etc.

[0031] like Figure 1 As shown, the motor drive device 100 according to the first embodiment of the present disclosure includes a pre-charging circuit 1, a rectifier 2, a smoothing capacitor 3, and an inverter 4. The pre-charging circuit 1 is sometimes referred to as an "initial charging circuit" or an "inrush current suppression circuit".

[0032] The rectifier 2 converts the input AC power into DC power and outputs the DC power to the DC output side of the rectifier 2, i.e., the DC link. The rectifier 2 is composed of a three-phase bridge circuit. Examples of the rectifier 2 include a PWM switching control rectifier, a diode rectifier, and a 120-degree conduction rectifier. Figure 1In the example shown, the rectifier 2 is composed of a PWM switch control rectifier. For example, when the rectifier 2 is composed of a PWM switch control rectifier or a 120-degree power-on rectifier, it is composed of a bridge circuit of a switching element and a diode connected in reverse parallel thereto, and each switching element is controlled to be turned on and off according to a drive instruction received from an upper control circuit (not shown), and power conversion is performed in both AC and DC directions. At this time, examples of the switching element include FET, IGBT, thyristor, GTO (Gate Turn-OFF thyristor), transistor, etc., and other switching elements may also be used.

[0033] The smoothing capacitor 3 is provided in a DC link between the DC output side of the rectifier 2 and the DC input side of the inverter 4. The smoothing capacitor 3 is sometimes referred to as a DC link capacitor. The smoothing capacitor 3 has a function of suppressing the pulsation amount of the DC output of the rectifier 2 and a function of storing the DC power used by the inverter 4 to generate AC power. Examples of the smoothing capacitor 3 include an electrolytic capacitor, a film capacitor, and the like.

[0034] The inverter 4 is connected to the DC output side of the rectifier 2 via the smoothing capacitor 3, converts the DC power in the DC link into AC power for driving the motor and outputs it to the AC output side of the inverter 4. The inverter 4 is composed of a bridge circuit of switching elements and diodes connected in antiparallel thereto. When the motor 6 is a three-phase AC motor, the inverter 4 is composed of a three-phase bridge circuit, and when the motor 6 is a single-phase AC motor, the inverter 4 is composed of a single-phase bridge circuit. Figure 1 In the example shown, the motor 6 is set as a three-phase AC motor, and therefore the inverter 4 is composed of a three-phase bridge circuit. Examples of switching elements include FET, IGBT, thyristor, GTO, transistor, etc., and other switching elements may also be used. The inverter 4 controls its power conversion operation, for example, by PWM switching control. That is, the inverter 4 receives a drive instruction (PWM switching instruction) from a higher-level control circuit (not shown), converts the DC power in the DC link into AC power for driving the motor, and outputs it to the motor 6. In addition, when the motor is regenerated, the inverter 4 receives a drive instruction (PWM switching instruction) from a higher-level control circuit (not shown), converts the AC power regenerated by the motor 6 into DC power, and outputs it to the DC link.

[0035] As with a general motor drive device, the power conversion operation of the inverter 4 is controlled according to the drive command generated by the upper control circuit. The upper control circuit generates a drive command for controlling the speed, torque or rotor position of the motor 6 according to the speed of the motor 6 (speed feedback), the current flowing through the winding of the motor 6 (current feedback), the specified torque command, and the operation program of the motor 6. In addition, the structure of the upper control circuit defined here is only an example. For example, the structure of the upper control circuit can be defined by terms such as a position command generation unit, a torque command generation unit, and a switch command generation unit. In addition, for example, when the rectifier 2 is composed of a PWM switch control rectifier or a 120-degree power-on rectifier, the power conversion operation of the rectifier 2 is controlled according to the drive command generated by the upper control circuit.

[0036] The pre-charging circuit 1 is provided between the three-phase AC power source 5 and the AC input side of the rectifier 2. The pre-charging circuit 1 includes a switch unit 11, a power source voltage detection circuit 12, a control unit 13, a current detection circuit 14, and a capacitor voltage detection circuit 15.

[0037] The switch unit 11 includes a switch element that electrically connects the three-phase AC power supply 5 to the AC input side of the rectifier 2 when turned on, and electrically disconnects the three-phase AC power supply 5 from the AC input side of the rectifier 2 when turned off. R , S-phase switching element S S And the T-phase switching element S T In the three-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2, an R-phase switching element S is provided in the R-phase power line. R , an S-phase switching element S is set on the S-phase power line S , set T-phase switching element S on the T-phase power line T .

[0038] R phase switching element S R , S-phase switching element S S And the T-phase switching element S T When turned on, the current flowing from the three-phase AC power supply 5 to the AC input side of the rectifier 2 is conducted, and when turned off, the three-phase AC power supply 5 and the AC input side of the rectifier 2 are electrically disconnected. R , S-phase switching element S S And the T-phase switching element S T Examples include IGBT, MOSFET, etc. For the R phase switching element S R , S-phase switching element S S And the T-phase switching element S T The diodes are connected in anti-parallel.

[0039] The power supply voltage detection circuit 12 detects the AC voltage (phase voltage or line voltage) of the three-phase AC power supply 5. Data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12 is transmitted to the control unit 13. The data related to the AC voltage value of the three-phase AC power supply 5 includes information related to the amplitude and phase of the AC voltage of the three-phase AC power supply 5. In addition, the data related to the AC voltage detected by the power supply voltage detection circuit 12 can also be used by the upper control circuit to control the power conversion operation of the rectifier 2.

[0040] The current detection circuit 14 detects the current of each phase flowing from the three-phase AC power supply 5 to the AC input side of the rectifier 2. Data related to the current value of each phase detected by the current detection circuit 14 is transmitted to the control unit 13. The data related to the current value of each phase includes information related to the amplitude and phase of the current. In addition, the data related to the current of each phase detected by the current detection circuit 14 can also be used by the upper control circuit to control the power conversion operation of the rectifier 2.

[0041] The capacitor voltage detection circuit 15 detects the voltage applied between the positive and negative terminals of the smoothing capacitor 3, that is, the capacitor voltage. In addition, the capacitor voltage detection circuit 15 can also detect the voltage between the terminals of the DC link, that is, the DC output side of the rectifier 2 (the potential difference between the positive potential on the DC output side of the rectifier 2 and the negative potential on the DC output side of the rectifier 2) as the capacitor voltage. Data related to the capacitor voltage value detected by the capacitor voltage detection circuit 15 is transmitted to the control unit 13. In addition, the data related to the capacitor voltage value detected by the capacitor voltage detection circuit 15 can also be used by the upper control circuit to control the power conversion operation of the inverter 4 and the power conversion operation of the rectifier 2.

[0042] The control unit 13 controls the switching element in the switch unit 11 to turn on and off based on the information related to the AC voltage detected by the power supply voltage detection circuit 12, thereby controlling the preparatory charging of the smoothing capacitor 3. When the control unit 13 controls the switching unit 11 to turn on and off for the preparatory charging of the smoothing capacitor 3, the data related to the current value of each phase detected by the current detection circuit 14 and the data related to the capacitor voltage value detected by the capacitor voltage detection circuit 15 may be used.

[0043] In addition, when the current detected by the current detection circuit 14 is an overcurrent, the control unit 13 controls all the switch elements of the switch unit 11 to be turned off, thereby electrically disconnecting the three-phase AC power supply 5 from the AC input side of the rectifier 2. As a result, the motor drive device can be protected from the overcurrent generated on the AC input side of the rectifier. In addition, when the switch unit 11 cuts off the overcurrent, a surge voltage may be generated. Therefore, the R-phase switch element S R , S-phase switching element S S And the T-phase switching element S T Connect surge absorption circuits such as varistors in parallel.

[0044] The control unit 13 performs the on / off control of the switch elements in the switch unit 11 for pre-charging as follows. In addition, when the rectifier 2 is composed of a PWM switching control type rectifier or a 120-degree conduction type rectifier, during the pre-charging period, all the switch elements in the rectifier 2 are turned off, and the rectifier 2 functions only as a diode rectifier.

[0045] First, during the preparatory charging period, the control unit 13 switches the R-phase switching element S to the R-phase switching element S according to the magnitude of the phase voltage of the AC voltage detected by the power supply voltage detection circuit 12. R , S-phase switching element S S And the T-phase switching element S T The switching element of the phase to be turned on is determined. The phase of the switching element to be turned on is called a "conduction phase". The control unit 13 determines the phase having the second largest phase voltage among the three-phase phase voltages detected by the power supply voltage detection circuit 12 as the conduction phase.

[0046] Then, the control unit 13 controls the switch element of the conducting phase to switch from off to on at the moment when the switch-on condition is satisfied. The moment when the switch-on condition is satisfied can be obtained by referring to data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. As the moment when the switch-on condition is satisfied, for example, one of the following is set. A first example of the moment when the switch-on condition is satisfied is a moment that is a first predetermined time τ1 earlier than the moment when the magnitude relationship between the phase voltage of the conducting phase and the phase voltage of the smallest phase is reversed. In addition, a second example of the moment when the switch-on condition is satisfied is a moment when the line voltage between the conducting phase and the smallest phase is a predetermined voltage threshold value V th At the following moment. By the switching element of the conducting phase turned on at the moment when the switch-on condition is satisfied, AC power flows from the three-phase AC power supply 5 to the AC input side of the rectifier 2. Then, the DC power flowing out from the AC output side of the rectifier 2 through the diode of the rectifier 2 flows into the smoothing capacitor 3, and the smoothing capacitor 3 is charged.

[0047] In addition, after the switch element of the conducting phase is turned on, the control unit 13 controls the switch element of the conducting phase to switch from on to off at the moment when the switch off condition is satisfied. The moment when the switch off condition is satisfied can be obtained by referring to the data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. Alternatively, the moment when the switch off condition is satisfied can be obtained by referring to the data related to the current value of each phase detected by the current detection circuit 14. As the moment when the switch off condition is satisfied, for example, one of the following is set. As a first example of the moment when the switch off condition is satisfied, it is the moment when the current flowing through the switch element of the conducting phase is approximately zero. The current flowing through the switch element of the conducting phase is detected by the current detection circuit 14. As a second example of the moment when the switch off condition is satisfied, it is the moment when the second specified time τ2 has passed since the magnitude of the phase voltage of the conducting phase is the smallest among the three-phase phase voltages.

[0048] An operation processing device (processor) is provided in the motor drive device 100 or in the pre-charging circuit 1. Examples of the operation processing device include IC, LSI, CPU, MPU, DSP, etc. In addition, the control unit 13 and the upper control circuit (not shown) may be composed of a combination of an analog circuit and an operation processing device, or may be composed of only an operation processing device, or may be composed of only an analog circuit. For example, in the case where the control unit 13 and the upper control circuit are constructed in the form of a software program, the functions of the control unit 13 and the upper control circuit can be realized by causing the operation processing device to operate according to the software program. Alternatively, the control unit 13 and the upper control circuit may be implemented as a semiconductor integrated circuit in which a software program for realizing the functions of each unit is written. Alternatively, the control unit 13 and the upper control circuit may be implemented as a recording medium in which a software program for realizing the functions of each unit is written. In addition, the control unit 13 may be provided in the upper control circuit.

[0049] Figure 2 1 is a flowchart showing the operation flow of the pre-charging process performed by the pre-charging circuit according to the first embodiment of the present disclosure. R , S-phase switching element S S And the T-phase switching element S T Execute All Figure 2 Steps S101 to S107.

[0050] Before the power supply of the motor drive device 100 is turned on, the R-phase switching element S in the switch unit 11 R , S-phase switching element S S And the T-phase switching element S TAll are disconnected. Therefore, the three-phase AC power supply 5 and the AC input side of the rectifier 2 are all electrically disconnected in the three-phase power line. In addition, the smoothing capacitor 3 is not charged. In addition, especially when the rectifier 2 is composed of a PWM switching control rectifier or a 120-degree power-on rectifier, during the preparatory charging period, all the switching elements in the rectifier 2 are disconnected, and the rectifier 2 functions only as a diode rectifier.

[0051] When the power of the motor drive device 100 is turned on, the pre-charging circuit 1 starts pre-charging the smoothing capacitor 3, and the process proceeds to step S101.

[0052] In step S101 , the control unit 13 determines the phase having the second largest phase voltage among the three-phase voltages detected by the power supply voltage detection circuit 12 as the conducting phase.

[0053] In step S102 , the control unit 13 determines whether the switch-on condition is satisfied. The process of step S102 is repeatedly executed at a cycle shorter than the power frequency of the three-phase AC power source 5 .

[0054] When it is determined in step S102 that the switch-on condition is satisfied, in step S103 , the control unit 13 performs control to switch the switch element of the conducting phase from off to on.

[0055] In step S104 , the control unit 13 determines whether the switch-off condition is satisfied. The process of step S104 is repeatedly executed at a cycle shorter than the power frequency of the three-phase AC power source 5 .

[0056] When it is determined in step S104 that the switch-off condition is satisfied, in step S105 , the control unit 13 performs control to switch the switch element of the conducting phase from on to off.

[0057] In step S106, the control unit 13 determines whether the pre-charging of the smoothing capacitor 3 is completed. When the capacitor voltage detected by the capacitor voltage detection circuit 15 reaches the predetermined charging voltage, the control unit 13 determines that the pre-charging of the smoothing capacitor 3 is completed, and proceeds to step S107. When the capacitor voltage detected by the capacitor voltage detection circuit 15 does not reach the predetermined charging voltage, the control unit 13 determines that the pre-charging of the smoothing capacitor 3 is not completed, and returns to step S101. The process of step S106 is repeatedly performed at a cycle shorter than the power supply frequency of the three-phase AC power supply 5.

[0058] When it is determined in step S106 that the pre-charging of the smoothing capacitor 3 is completed, in step S107, the control unit 13 switches the R-phase switching element S in the switching unit 11 to the ON position. R , S-phase switching element S S And the T-phase switching element ST After the pre-charging of the smoothing capacitor 3 is completed, the R-phase switching element S R , S-phase switching element S S And the T-phase switching element S T The three-phase AC power source 5 is turned on, so AC power flows from the three-phase AC power source 5 to the AC input side of the rectifier 2, and the rectifier 2 is turned on to a state where the motor 6 can be driven. The inverter 4 converts the DC power in the DC link into AC power for driving the motor and outputs it to the AC output side of the inverter 4. The motor 6 is driven by the AC power for driving the motor output from the AC output side of the inverter 4.

[0059] Figure 3 This is a flowchart showing the flow of operation of overcurrent protection processing performed by the motor drive device including the pre-charging circuit according to the first to third embodiments of the present disclosure. Figure 3 The flowchart shown can also be applied to the second and third embodiments described later.

[0060] As reference Figure 1 and Figure 2 As described above, after the pre-charging of the smoothing capacitor 3 is completed, the motor drive device 100 drives the motor 6 using the motor driving AC power output from the AC output side of the inverter 4. During the driving of the motor 6, in step S201, the current detection circuit 14 detects the current of each phase flowing from the three-phase AC power supply 5 to the AC input side of the rectifier 2.

[0061] In step S202, the control unit 13 determines whether an overcurrent has occurred based on the current detected by the current detection circuit 14. For example, the control unit 13 determines that an overcurrent has occurred when the peak value of the current detected by the current detection circuit 14 exceeds a predetermined threshold value within a predetermined period. In step S202, if an overcurrent has been detected, the process proceeds to step S203, and if an overcurrent has not been detected, the process returns to step S201. The process of step S202 is repeatedly performed at a predetermined cycle.

[0062] If it is determined in step S202 that an overcurrent has occurred, in step S203 the control unit 13 switches the R-phase switching element S in the switch unit 11. R , S-phase switching element S S And the T-phase switching element S T Control of all disconnection: Thus, the three-phase AC power source 5 and the AC input side of the rectifier 2 are completely electrically disconnected, and the motor drive device 100 can be protected from overcurrent.

[0063] In addition, the overcurrent protection process performed by the pre-charging circuit 1 may be executed during the pre-charging process performed by the pre-charging circuit 1. In this case, for example, Figure 2 The first stage of each of steps S101 to S107 is executed Figure 3 The overcurrent protection process performed by the preparatory charging circuit 1 shown is sufficient.

[0064] Figure 4 1 is a waveform diagram showing a specific example of the operation of the switch unit in the pre-charging process performed by the pre-charging circuit of the first embodiment of the present disclosure. Figure 4 , the R-phase voltage of the three-phase AC power supply 5 is represented by a bold solid line, the S-phase voltage is represented by a bold dotted line, and the T-phase voltage is represented by a bold single-dot chain line.

[0065] Here, as an example, the R-phase switching element S in the switching unit 11 is described. R Perform on / off control.

[0066] In the interval A1, the R phase voltage is the largest among the three-phase voltages of the three-phase AC power source 5. Therefore, the R-phase-S-phase line voltage (S-phase reference) V RS And the line voltage between R phase and T phase (T phase reference) V RT Assume that the R-phase switching element S is turned on in interval A1. R , then from the three-phase AC power supply 5 through the R phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the S-phase switching element S S There is a risk that a large current will flow through the path of the diode connected in anti-parallel to the three-phase AC power supply 5. Therefore, in the interval A1, the R-phase switching element S is kept turned on. R Disconnected state.

[0067] In the interval A2, the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, and the R-phase voltage is the second largest phase voltage. In the interval A2, the R-phase-S-phase line voltage (S-phase reference) V RS Therefore, even if the R-phase switching element S is turned on in interval A2 R , from the three-phase AC power supply 5 through the R phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the S-phase switching element S S The current does not flow in the path to the three-phase AC power supply 5 through the diode connected in antiparallel. R When connected, the line voltage between R phase and T phase (T phase reference) V RTThe current corresponding to the magnitude is transmitted from the three-phase AC power supply 5 through the R phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase switching element S T The voltage flows through the antiparallel-connected diodes and reaches the three-phase AC power supply 5. In section A2, the R-phase-T-phase line voltage (T-phase reference) V RT Therefore, if the R-phase switching element S is turned on at the end of interval A2, R , a large current will not flow. Therefore, in the first embodiment, the R phase having the second largest phase voltage among the three-phase voltages is determined to be the conducting phase. And, at a time earlier than the time when the magnitude relationship between the R phase voltage of the conducting phase and the T phase voltage of the smallest phase is reversed (the time when the interval A2 is switched to the interval A3) by the first predetermined time τ1, the R phase switching element S as the conducting phase is switched to the conducting phase. R Alternatively, the line voltage (T phase reference) V between the R phase, which is the conducting phase, and the T phase, which has the smallest magnitude, is switched from off to on. RT The voltage threshold V th At the following moment, the R-phase switching element S is turned on. R Switching from off to on. The shorter the first predetermined time τ1 is, or the voltage threshold V th The smaller the R-phase-T-phase line voltage (T-phase reference) V RT Therefore, even if the R-phase switching element S is turned on R , from the three-phase AC power supply 5 through the R phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase switching element S T A large current does not flow in the path through the diodes connected in anti-parallel to the three-phase AC power supply 5 .

[0068] In the section A3, the R phase voltage is the smallest among the three-phase voltages of the three-phase AC power supply 5. Therefore, in the section A3, the R-S phase line voltage (S phase reference) V RS Therefore, even if the R phase switching element S R In the on state, the three-phase AC power supply 5 is connected via the R-phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the S-phase switching element S SNo current flows in the path to the three-phase AC power supply 5 through the diodes connected in antiparallel. Similarly, the line voltage (T-phase reference) V RT Therefore, even if the R phase switching element S R In the on state, the three-phase AC power supply 5 is connected via the R-phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase switching element S T In the path from the diode connected in antiparallel to the three-phase AC power supply 5, no current flows. That is, in the interval A3, the R-phase switching element S R No current flows in the R phase switching element S R When switching from on to off, no surge voltage is generated and no switching loss is generated. Therefore, in the first embodiment, when the R phase switching element S of the conducting phase flows, R When the current is substantially zero, or when the R-phase voltage of the conducting phase becomes the minimum of the three-phase voltages and a second predetermined time τ2 has passed, the R-phase switching element S is switched to R Switches from on to off.

[0069] In the interval A4, the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, and the R-phase voltage is the second largest phase voltage. R When the three-phase AC power source 5 is connected via the R-phase switching element S R , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the S-phase switching element S S There is a risk that a large current will flow through the path of the diode connected in antiparallel to the three-phase AC power supply 5. R Switching from on to off generates a surge voltage and increases the switching loss. Therefore, as described above, in the stage of interval A3 before entering interval A4, the R phase switching element S R The R-phase switching element S is switched from on to off. R Disconnected state.

[0070] Above, refer to Figure 4 The R-phase switching element S in the switching unit 11 is R The above description can also be applied to the on-off control of the S-phase switching element S SThe on / off control of the T-phase switching element S T When the above description is applied to the S-phase switching element S S In the case of on / off control, the R-phase switching element S described above is R Replaced with S-phase switching element S S , the S-phase switching element S described above S Replaced with T-phase switching element S T , the T-phase switching element S described above T Replaced with R phase switching element S S In addition, when the above description is applied to the T-phase switching element S T In the case of on / off control, the R-phase switching element S described above is R Replaced with T-phase switching element S T , the S-phase switching element S described above S Replaced with R phase switching element S R , the T-phase switching element S described above T Replaced with S-phase switching element S S That is, during the pre-charging process of the pre-charging circuit 1, the control unit 13 controls the R-phase switching element S in the switch unit 11. R , S-phase switching element S S And the T-phase switching element S T On and off control is performed appropriately respectively.

[0071] As described above, the motor drive device 100 having the pre-charging circuit 1 of the first embodiment of the present disclosure has both a pre-charging function and a power supply cut-off function when an overcurrent occurs. According to the first embodiment of the present disclosure, a pre-charging circuit capable of cutting off the power supply when an overcurrent occurs on the AC input side of the rectifier 2 can be realized.

[0072] In the past, in order to protect the motor drive device from overcurrent, a circuit breaker or a fuse was set on the AC input side of the rectifier. However, in order to prevent the circuit breaker or the fuse from malfunctioning during the normal operation of the motor, it is necessary to select a circuit breaker or a fuse with a large rating with a margin. In addition, the circuit breaker or the fuse is a mechanical on-off switch, so the opening and closing action is slow, and the power supply is cut off slowly when an overcurrent occurs, and sometimes the motor drive device cannot be protected. In contrast, in the preparatory charging circuit of the first embodiment of the present disclosure, a semiconductor switching element is set as a switch unit 11 that electrically connects the three-phase AC power supply 5 and the AC input side of the rectifier 2 when connected and electrically cuts off the three-phase AC power supply 5 and the AC input side of the rectifier 2 when disconnected, so that the power supply can be quickly cut off when an overcurrent occurs, and the motor drive device can be protected more reliably. In addition, there is no need to set a circuit breaker or a fuse as in the past, so it is helpful to miniaturize and reduce the cost of the motor drive device.

[0073] In addition, the conventional pre-charging circuit includes a resistor and a switch connected in parallel with the resistor. In contrast, the pre-charging circuit of the first embodiment of the present disclosure does not include a charging resistor, thereby making it possible to reduce the size and cost of the motor drive device.

[0074] <Second embodiment>

[0075] Figure 5 It is a diagram showing a pre-charging circuit and a motor drive device according to a second embodiment of the present disclosure.

[0076] like Figure 5 As shown, the pre-charging circuit 1 of the second embodiment of the present disclosure has the following switching elements as the switching section 11 in two phases of the three-phase power line between the three-phase AC power source and the AC input side of the rectifier: the switching elements can be turned on and off in both directions from the three-phase AC power source 5 to the AC input side of the rectifier 2 and from the AC input side of the rectifier 2 to the three-phase AC power source 5. Each switching element can selectively switch the following states: conduction of current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power source 5 toward the AC input side of the rectifier 2 when it is turned on; conduction of current flowing in a second conduction direction, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power source 5 when it is turned on; and electrical disconnection between the three-phase AC power source 5 and the AC input side of the rectifier 2 when it is turned off.

[0077] Regarding the rectifier 2, the smoothing capacitor 3, the inverter 4, the three-phase AC power supply 5, the motor 6, the power supply voltage detection circuit 12, the current detection circuit 14 and the capacitor voltage detection circuit 15, as shown in FIG. Figure 1 to Figure 4 As described.

[0078] exist Figure 5 In the example shown, as an example, the switch unit 11 in the pre-charging circuit 1 includes a first R-phase switching element S provided on the R-phase power line. R1 and the second R-phase switching element S R2 , and a first S-phase switching element S provided on the S-phase power line S1 and the second S-phase switching element S S2 .

[0079] A first R-phase switching element S is provided on the R-phase power line of the three-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2. R1 and the second R-phase switching element S R2 The first R-phase switching element S R1 and the second R-phase switching element S R2 The first R-phase switching element S is connected in anti-parallel so that the conducting direction when turned on is opposite to that when turned on. R1 When turned on, the second R-phase switching element S conducts a current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power supply 5 toward the AC input side of the rectifier 2. R2 When turned on, the current flowing in the second conduction direction is conducted, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power supply 5. R1 and the second R-phase switching element S R2 When both are disconnected, the three-phase AC power source 5 and the AC input side of the rectifier 2 are electrically disconnected in the R-phase power line.

[0080] The first S-phase switching element S is provided on the S-phase power line of the three-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2. S1 and the second S-phase switching element S S2 The first S-phase switching element S S1 and the second S-phase switching element S S2 The first S-phase switching element S is connected in anti-parallel so that the conducting direction when turned on is opposite to that when turned on. S1 When turned on, the second S-phase switching element S conducts a current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power supply 5 toward the AC input side of the rectifier 2. S2 When turned on, the current flowing in the second conduction direction is conducted, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power supply 5. S1 and the second S-phase switching element S S2 When both are disconnected, the three-phase AC power source 5 and the AC input side of the rectifier 2 are electrically cut off in the S-phase power line.

[0081] The control unit 13 controls the switching element in the switch unit 11 to turn on and off based on information on the AC voltage detected by the power supply voltage detection circuit 12 , thereby controlling the pre-charging of the smoothing capacitor 3 .

[0082] In addition, when the current detected by the current detection circuit 14 is an overcurrent, the control unit 13 controls all the switch elements in the switch unit 11 to be turned off, thereby electrically disconnecting the three-phase AC power supply 5 from the AC input side of the rectifier 2. In the overcurrent protection process of the second embodiment, Figure 3 Flowchart shown.

[0083] The on / off control of the switch unit 11 for pre-charging by the control unit 13 is performed as follows. When the rectifier 2 is a PWM switching control rectifier or a 120-degree conduction rectifier, during the pre-charging period, all the switching elements in the rectifier 2 are turned off, and the rectifier 2 functions only as a diode rectifier.

[0084] The control unit 13 controls the switch element to switch from off to on at the moment when the switch-on condition is satisfied. The moment when the switch-on condition is satisfied can be obtained by referring to data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. As the moment when the switch-on condition is satisfied, for example, one of the following is set. A first example of the moment when the switch-on condition is satisfied is a moment that is a first specified time τ1 earlier than the moment when the magnitude relationship between the phase with the switch element and the phase without the switch element in the three-phase phase voltage detected by the power supply voltage detection circuit 12 is reversed. Figure 5 In the example shown, the timing is a first predetermined time τ1 before the timing when the magnitude relationship between the T-phase voltage and the R-phase or S-phase voltage is reversed as detected by the power supply voltage detection circuit 12. A second example of the timing that satisfies the switch-on condition is when the three-phase line voltage detected by the power supply voltage detection circuit 12 reaches a predetermined voltage threshold value V th The following moment. Figure 5 In the example shown, the absolute value of the R-phase-T-phase line voltage or the absolute value of the S-phase-T-phase line voltage detected by the power supply voltage detection circuit 12 is the predetermined voltage threshold value V th At the moment when the switch-on condition is satisfied, the control unit 13 controls the switching element of the phase where the line voltage of the T-phase reference switches from positive to negative detected by the power supply voltage detection circuit 12 to switch from off to on so as to conduct the current flowing in the first conduction direction. Alternatively, at this moment, the control unit 13 controls the switching element of the phase where the line voltage of the T-phase reference switches from negative to positive detected by the power supply voltage detection circuit 12 to switch from off to on so as to conduct the current flowing in the second conduction direction.

[0085] In addition, after the switch element (i.e., the switch element that is the control object of switching from disconnection to connection as described above) is turned on, the control unit 13 controls the switch element to switch from on to off at the moment when the switch disconnection condition is satisfied. The moment when the switch disconnection condition is satisfied can be obtained by referring to data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. Alternatively, the moment when the switch disconnection condition is satisfied can be obtained by referring to data related to the current values ​​of each phase detected by the current detection circuit 14. As the moment when the switch disconnection condition is satisfied, for example, one of the following is set. As a first example of the moment when the switch disconnection condition is satisfied, it is the moment when the current flowing through the switched-on switch element is substantially zero. As a second example of the moment when the switch disconnection condition is satisfied, it is the moment when the second prescribed time τ2 has passed since the moment when the line voltage switches from positive to negative and from negative to positive.

[0086] Figure 6 : is a waveform diagram showing a specific example of the operation of the switch unit in the pre-charging process performed by the pre-charging circuit of the second embodiment of the present disclosure. Figure 6 , the R-phase voltage of the three-phase AC power supply 5 is represented by a bold solid line, the S-phase voltage is represented by a bold dotted line, and the T-phase voltage is represented by a bold single-dot chain line.

[0087] Here, as an example, a first R-phase switching element S is provided on the R-phase power line. R1 and the second R-phase switching element S R2 , a first S-phase switching element S is provided on the S-phase power line S1 and the second S-phase switching element S S2 In the case of the first R-phase switching element S R1 and the second R-phase switching element S R2 Perform on / off control.

[0088] In the interval A1, the R phase voltage is the largest among the three-phase voltages of the three-phase AC power supply 5. Therefore, the R-phase-T-phase line voltage (T-phase reference) V is based on the T-phase directly connected to the power supply. RT Assume that the first R-phase switching element S is turned on in interval A1. R1 When the three-phase AC power source 5 is connected to the first R-phase switching element S R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase power line to reach the three-phase AC power source 5, there is a risk of a large current flowing. Therefore, in the interval A1, the first R-phase switching element S is maintained R1In addition, in the interval A1, as described later, the second R-phase switching element S R2 Continue to connect from section A4.

[0089] In the section A2, the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, and the R-phase voltage becomes the second largest phase voltage.

[0090] Assume that in the interval A2, the second R-phase switching element S R2 When the on state is maintained, the three-phase AC power source 5 is connected via the first S-phase switching element S S1 , diode D of the upper arm of the S phase of rectifier 2 SU , smoothing capacitor 3, diode D of the R-phase lower arm of rectifier 2 RL , and the second R-phase switching element S R2 Therefore, in the second embodiment, the current flows through the second R-phase switching element S which is turned on. R2 When the current is approximately zero, or when the voltage between the R phase and the T phase (T phase reference) V RT When the second predetermined time τ2 has elapsed from the time of switching from negative to positive (the time of switching from interval A4 to interval A1 for the R phase), the second R phase switching element S R2 Performs control from on to off.

[0091] On the other hand, in section A2, the R-phase-T-phase line voltage (T-phase reference) V RT Assume that in interval A2, the first R-phase switching element S R1 When the three-phase AC power source 5 is switched on, the first R-phase switching element S R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase power line to the three-phase AC power source 5. If the first R-phase switching element S is switched off at the end of the interval A2, the current flows through the path of the R-phase power line and the T-phase power line to the three-phase AC power source 5. R1 Therefore, in the second embodiment, at a time τ1 earlier than the time when the magnitude relationship between the T-phase voltage and the R-phase or S-phase voltage is reversed (the time when the R-phase switches from the interval A2 to the interval A3), or at a time when the line voltage (T-phase reference) V between the R-phase and the smallest T-phase is reversed, the voltage is turned on. RT The voltage threshold V th At the following time, for the R-phase-T-phase line voltage (T-phase reference) V RT The first R-phase switching element S switched from positive to negative R1, control is performed to switch from off to on so as to conduct the current flowing in the first conduction direction.

[0092] In the section A3, the R-phase voltage among the three-phase voltages of the three-phase AC power source 5 is the smallest. R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase power line to reach the three-phase AC power supply 5. In the interval A3, the R-phase-T-phase line voltage (T-phase reference) V RT is negative, and the second R phase switching element S R2 Therefore, in the second embodiment, the current flows through the first R-phase switching element S which is turned on. R1 The R-phase-T-phase line voltage (T-phase reference) V RT The first R-phase switching element S switched from positive to negative R1 , and perform control from on to off.

[0093] In the section A4 , the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, and the R-phase voltage becomes the second largest phase voltage.

[0094] Assume that in the interval A4, the first R-phase switching element S R1 and the second S-phase switching element S S2 When the three-phase AC power source 5 is switched on, the first R-phase switching element S R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the S-phase power line to reach the three-phase AC power supply 5, there is a risk of a large current flowing. R1 and the second S-phase switching element S S2 Maintain disconnection.

[0095] On the other hand, the R-phase-T-phase line voltage (T-phase reference) V RT The absolute value of gradually decreases. In the interval A4, the second R-phase switching element S R2 When the power is turned on, the three-phase AC power source 5 passes through the T-phase power line and the diode D of the T-phase upper arm of the rectifier 2. TU , smoothing capacitor 3, diode D of the R-phase lower arm of rectifier 2RL , the second R-phase switching element S R2 The current flows through the path to the three-phase AC power supply 5. R2 Therefore, in the second embodiment, at a time τ1 earlier than the time when the magnitude relationship between the T-phase voltage and the R-phase or S-phase voltage is reversed (the time when the R-phase switches from the interval A3 to the interval A4), or at a time when the line voltage (T-phase reference) V between the R-phase and the smallest T-phase is reversed, the voltage is turned on. RT The absolute value of the voltage becomes the specified threshold value V th At the following time, for the R-phase-T-phase line voltage (T-phase reference) V RT The second R-phase switching element S switched from negative to positive R2 , control is performed to switch from off to on so that the current flowing in the second conduction direction is conducted.

[0096] The interval A4 is followed by the interval A1, and the above-mentioned on / off control is performed again.

[0097] Above, refer to Figure 6 The first R-phase switching element S in the switching unit 11 is described. R1 and the second R-phase switching element S R2 The above description can also be applied to the first S-phase switching element S S1 and the second S-phase switching element S S2 During the pre-charging process of the pre-charging circuit 1, the control unit 13 controls the first R-phase switching element S in the switch unit 11. R1 , the second R-phase switching element S R2 , the first S-phase switching element S S1 and the second S-phase switching element S S2 On and off control is performed appropriately respectively.

[0098] In addition, Figure 6 In the embodiment, a first R-phase switching element S is provided on the R-phase power line. R1 and the second R-phase switching element S R2 , a first S-phase switching element S is provided on the S-phase power line S1 and the second S-phase switching element S S2 The above description can also be applied to the case where the first S-phase switching element S is provided in the S-phase power line. S1 and the second S-phase switching element S S2 , a first T-phase switching element S is provided on the T-phase power line T1 and the second T-phase switching element S T2Similarly, the above description can also be applied to the case where the first R-phase switching element S is provided in the R-phase power line. R1 and the second R-phase switching element S R2 , a first T-phase switching element S is provided on the T-phase power line T1 and the second T-phase switching element S T2 Example.

[0099] In addition to the effects of the first embodiment, the second embodiment of the present disclosure has the advantage of being able to reduce the diode provided in the pre-charging circuit in the first embodiment. In addition, the second embodiment of the present disclosure has an advantage of being able to shorten the time required to complete pre-charging because the conduction frequency is increased compared to the first embodiment.

[0100] <Third Embodiment>

[0101] Figure 7 It is a diagram showing a pre-charging circuit and a motor drive device according to a third embodiment of the present disclosure.

[0102] like Figure 7 As shown, the pre-charging circuit 1 of the third embodiment of the present disclosure has the following switching elements as the switching section 11 in the three-phase power line between the three-phase AC power source and the AC input side of the rectifier: the switching element can be turned on and off in both directions from the three-phase AC power source 5 to the AC input side of the rectifier 2 and from the AC input side of the rectifier 2 to the three-phase AC power source 5. Each switching element can selectively switch the following states: conduction of current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power source 5 toward the AC input side of the rectifier 2 when it is turned on; conduction of current flowing in a second conduction direction, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power source 5 when it is turned on; and electrical disconnection between the three-phase AC power source 5 and the AC input side of the rectifier 2 when it is turned off.

[0103] Regarding the rectifier 2, the smoothing capacitor 3, the inverter 4, the three-phase AC power supply 5, the motor 6, the power supply voltage detection circuit 12, the current detection circuit 14 and the capacitor voltage detection circuit 15, as shown in FIG. Figure 1 to Figure 4 As described.

[0104] A first R-phase switching element S is provided on the R-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2. R1 and the second R-phase switching element S R2 The first R-phase switching element S R1 and the second R-phase switching element S R2 The first R-phase switching element S is connected in anti-parallel so that the conducting direction when turned on becomes the opposite direction. R1When turned on, the second R-phase switching element S conducts a current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power supply 5 toward the AC input side of the rectifier 2. R2 When turned on, the current flowing in the second conduction direction is conducted, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power supply 5. R1 and the second R-phase switching element S R2 When both are disconnected, the three-phase AC power source 5 and the AC input side of the rectifier 2 are electrically disconnected in the R-phase power line.

[0105] A first S-phase switching element S is provided on the S-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2. S1 and the second S-phase switching element S S2 The first S-phase switching element S S1 and the second S-phase switching element S S2 The first S-phase switching element S is connected in antiparallel so that the conducting direction when turned on becomes the opposite direction. S1 When turned on, the second S-phase switching element S conducts a current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power supply 5 toward the AC input side of the rectifier 2. S2 When turned on, the current flowing in the second conduction direction is conducted, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power supply 5. S1 and the second S-phase switching element S S2 When both are disconnected, the three-phase AC power source 5 and the AC input side of the rectifier 2 are electrically cut off in the S-phase power line.

[0106] A first T-phase switching element S is provided on the T-phase power line between the three-phase AC power source 5 and the AC input side of the rectifier 2. T1 and the second T-phase switching element S T2 The first T-phase switching element S T1 and the second T-phase switching element S T2 The first T-phase switching element S is connected in anti-parallel so that the conducting direction when turned on is opposite to that when turned on. T1 When turned on, the second T-phase switching element S conducts a current flowing in a first conduction direction, wherein the first conduction direction is from the three-phase AC power supply 5 toward the AC input side of the rectifier 2. T2 When turned on, the current flowing in the second conduction direction is conducted, wherein the second conduction direction is from the AC input side of the rectifier 2 toward the three-phase AC power supply 5. T1 and the second T-phase switching element S T2When both are disconnected, the three-phase AC power source 5 and the AC input side of the rectifier 2 are electrically cut off in the T-phase power line.

[0107] The control unit 13 controls the switching unit 11 to turn on and off based on information on the AC voltage detected by the power supply voltage detection circuit 12 , thereby controlling the pre-charging of the smoothing capacitor 3 .

[0108] In addition, when the current detected by the current detection circuit 14 is an overcurrent, the control unit 13 controls all the switch elements in the switch unit 11 to be turned off, thereby electrically disconnecting the three-phase AC power supply 5 from the AC input side of the rectifier 2. Figure 3 Flowchart shown.

[0109] The on / off control of the switch unit 11 for pre-charging by the control unit 13 is performed as follows. When the rectifier 2 is a PWM switching control rectifier or a 120-degree conduction rectifier, during the pre-charging period, all the switching elements in the rectifier 2 are turned off, and the rectifier 2 functions only as a diode rectifier.

[0110] The control unit 13 controls the switch element to switch from off to on at the moment when the switch-on condition is satisfied. The moment when the switch-on condition is satisfied can be obtained by referring to data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. As the moment when the switch-on condition is satisfied, for example, one of the following is set. A first example of the moment when the switch-on condition is satisfied is a moment that is a first predetermined time τ1 earlier than the moment when the magnitude relationship of the three-phase phase voltage detected by the power supply voltage detection circuit 12 is reversed. A second example of the moment when the switch-on condition is satisfied is a moment when the three-phase line voltage detected by the power supply voltage detection circuit 12 becomes a predetermined voltage threshold value V th At the moment when the switch-on condition is satisfied, the control unit 13 controls the switching element of the phase where the three-phase line voltage detected by the power supply voltage detection circuit 12 switches from positive to negative, from off to on, so that the current flowing in the first conduction direction is conducted. At this moment, the switching element of the phase where the three-phase line voltage detected by the power supply voltage detection circuit 12 switches from negative to positive is controlled to switch from off to on, so that the current flowing in the second conduction direction is conducted.

[0111] In addition, after the switch element (i.e., the switch element that is the control object of switching from disconnection to connection as described above) is turned on, the control unit 13 controls the switch element to switch from on to off at the moment when the switch disconnection condition is satisfied. The moment when the switch disconnection condition is satisfied can be obtained by referring to data related to the AC voltage value of the three-phase AC power supply 5 detected by the power supply voltage detection circuit 12. Alternatively, the moment when the switch disconnection condition is satisfied can be obtained by referring to data related to the current values ​​of each phase detected by the current detection circuit 14. As the moment when the switch disconnection condition is satisfied, for example, one of the following is set. As a first example of the moment when the switch disconnection condition is satisfied, it is the moment when the current flowing through the switched-on switch element is substantially zero. As a second example of the moment when the switch disconnection condition is satisfied, it is the moment when the second prescribed time τ2 has passed since the moment when the line voltage switches from positive to negative and from negative to positive.

[0112] Figure 8 : is a waveform diagram showing a specific example of the operation of the switch unit in the pre-charging process performed by the pre-charging circuit of the third embodiment of the present disclosure. Figure 8 , the R-phase voltage of the three-phase AC power supply 5 is represented by a bold solid line, the S-phase voltage is represented by a bold dotted line, and the T-phase voltage is represented by a bold single-dot chain line.

[0113] Here, as an example, the first R-phase switching element S R1 , the second S-phase switching element S S2 and the second T-phase switching element S T2 Perform on / off control.

[0114] In the section A1, the R phase voltage is the largest among the three-phase voltages of the three-phase AC power source 5. R-phase-S-phase line voltage (S-phase reference) V RS Gradually decreases, but the R-phase-T-phase line voltage (T-phase reference) V RT If the first R-phase switching element S is switched to R1 and the second S-phase switching element S S2 Therefore, in the third embodiment, at a time τ1 earlier than the time when the magnitude relationship of the three-phase voltage detected by the power supply voltage detection circuit 12 is reversed (the time when the R phase and the S phase switch from the interval A1 to the interval A2), or at a time when the line voltage between the R phase and the S phase (S phase reference) V RS The voltage threshold V th At the following time, for the R-phase-S-phase line voltage (S-phase reference) V RS The first R-phase switching element S switched from positive to negative R1, switching from off to on is performed to conduct the current flowing in the first conduction direction, and the S-phase-R-phase line voltage (R-phase reference) V SR The second S-phase switching element S switched from negative to positive S2 , the control is switched from off to on so that the current flowing in the second conduction direction is conducted. R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the S-phase lower arm of rectifier 2 SL , and the second S-phase switching element S S1 Then, current flows through the path to the three-phase AC power supply 5 .

[0115] In section A2, the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, and the R-phase voltage becomes the second largest phase voltage. The line voltage between the R-phase and S-phase (S-phase reference) V RS Therefore, in the third embodiment, when the first R-phase switching element S is turned on, R1 and the second S-phase switching element S S1 When the current is approximately zero, or when the R-S line voltage (S-phase reference) V RS At the time when the second predetermined time τ2 has passed since the time of switching from positive to negative (the time of switching from section A1 to section A2), the R-phase-S-phase line voltage (S-phase reference) V RS The first R-phase switching element S switched from positive to negative R1 , and S-phase-R-phase line voltage (S-phase reference) V SR The second S-phase switching element S switched from negative to positive S1 , and perform control from on to off.

[0116] In the section A2, the S phase voltage is the largest among the three phase voltages of the three phase AC power source 5. RS Gradually increases, but the R-T phase line voltage (T phase reference) V RT If the first R-phase switching element S is switched off at the end of interval A2 R1 and the second T-phase switching element S T2 Therefore, in the third embodiment, at a time τ1 earlier than the time when the magnitude relationship of the three-phase voltage detected by the power supply voltage detection circuit 12 is reversed (the time when the R phase and the T phase switch from the interval A2 to the interval A3), or at a time when the line voltage between the R phase and the T phase (T phase reference) V RT The voltage threshold V thAt the following time, for the R-phase-T-phase line voltage (T-phase reference) V RT The first R-phase switching element S switched from positive to negative R1 , switching from off to on is controlled so that the current flowing in the first conduction direction is conducted, and the T-phase-R-phase line voltage (R-phase reference) V TR The second T-phase switching element S switched from negative to positive T2 , the control is switched from off to on so that the current flowing in the second conduction direction is conducted. R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the second T-phase switching element S T1 Then, current flows through the path to the three-phase AC power supply 5 .

[0117] In the section A3, the R-phase voltage among the three-phase voltages of the three-phase AC power source 5 is the smallest. R1 , diode D of the upper arm of the R phase of rectifier 2 RU , smoothing capacitor 3, diode D of the lower arm of the T phase of rectifier 2 TL , and the T-phase power line to reach the three-phase AC power supply 5. In the interval A3, the R-phase-T-phase line voltage (T-phase reference) V RT is negative, so the current does not flow. Therefore, in the third embodiment, when the current flows through the first R-phase switching element S R1 and the second T-phase switching element S T2 When the current is approximately zero, or when the voltage between the R phase and the T phase (T phase reference) V RT Switching from positive to negative and T-phase-R-phase line voltage (R-phase reference) V TR At the time when the second predetermined time τ2 has passed since the time of switching from negative to positive (the time of switching from section A2 to section A3 for R phase and T phase), the R phase-T phase line voltage (T phase reference) V RT The first R-phase switching element S switched from positive to negative R1 , and the T-phase-R-phase line voltage (R-phase reference) V TR The second T-phase switching element S switched from negative to positive T2 , and perform control from on to off.

[0118] In section A4, the magnitude relationship between the R-phase voltage and the S-phase voltage is reversed, but the R-phase-S-phase line voltage (S-phase reference) V RSTherefore, for the first R-phase switching element S R1 and the second S-phase switching element S S2 Maintain disconnection.

[0119] After the section A4 , the section A1 continues, and the above-mentioned on / off control is performed again.

[0120] Above, refer to Figure 8 The first R-phase switching element S in the switching unit 11 is described. R1 , the second S-phase switching element S S2 and the second T-phase switching element S T2 The above description can also be applied to the first S-phase switching element S S1 , the second T-phase switching element S T2 and the second R-phase switching element S R2 The on / off control of the first T-phase switching element S T1 , the second R-phase switching element S R2 and the second S-phase switching element S S2 During the pre-charging process of the pre-charging circuit 1, the control unit 13 controls the first R-phase switching element S in the switch unit 11. R1 , the second R-phase switching element S R2 , the first S-phase switching element S S1 and the second S-phase switching element S S2 , the first T-phase switching element S T1 and the second T-phase switching element S T2 On and off control is performed appropriately respectively.

[0121] In addition to the effects of the first and second embodiments, the third embodiment of the present disclosure has the advantage that the phase of the switching element to be turned on does not need to be limited to the phase having the second phase voltage among the three-phase voltage. In addition, the third embodiment of the present disclosure has an advantage that the conduction frequency is increased compared to the first and second embodiments, and therefore, the time required to complete the preparatory charging can be shortened.

[0122] <Matters commonly applied to the first to third embodiments>

[0123] When the smoothing capacitor 3 is charged by the pre-charging circuit 1 of the first to third embodiments of the present disclosure, the voltage of the smoothing capacitor 3 gradually increases. Therefore, if the first predetermined time τ1 or the voltage threshold V thIf the pre-charging of the pre-charging circuit 1 is continued while maintaining a fixed value, the difference between the voltage of the smoothing capacitor 3 and the line voltage of the three-phase AC power supply 5 gradually decreases. When the difference between the voltage of the smoothing capacitor 3 and the line voltage of the three-phase AC power supply 5 gradually decreases, the power flowing from the three-phase AC power supply 5 via the rectifier 2 to the smoothing capacitor 3 gradually decreases, and the charging function of the pre-charging circuit 1 for the smoothing capacitor 3 gradually decreases.

[0124] Therefore, in the first to third embodiments of the present disclosure, during the pre-charging period of the pre-charging circuit 1, the first predetermined time τ1 or the voltage threshold V used when the control unit 13 switches the switching element in the switch unit 11 from off to on is gradually changed. th The first specified time τ1 or voltage threshold V th For example, it is stored in a rewritable storage unit (not shown) in the pre-charging circuit 1. The storage unit may be composed of an electrically erasable / recordable nonvolatile memory such as EEPROM (registered trademark) or a high-speed readable and writable random access memory such as DRAM or SRAM.

[0125] Below, several first specified time τ1 or voltage threshold V are listed. th method of changing.

[0126] In the first changing method, the first predetermined time τ1 or the voltage threshold value V used when the switching element in the switching unit 11 is switched from off to on by the control unit 13 is changed according to the voltage of the smoothing capacitor 3 detected by the capacitor voltage detection circuit 15. th That is, the larger the voltage of the smoothing capacitor 3 detected by the capacitor voltage detection circuit 15 is, the longer the first predetermined time τ1 is made, or the voltage threshold V th As a result, the larger the voltage of the smoothing capacitor 3 is, the longer the on-time of the switching element in the switch unit 11 is. Therefore, it is possible to suppress the gradual reduction of the power flowing from the three-phase AC power supply 5 via the rectifier 2 into the smoothing capacitor 3, and to maintain the charging function of the pre-charging circuit 1 for the smoothing capacitor 3.

[0127] In the second changing method, the first predetermined time τ1 or the voltage threshold V used when the control unit 13 switches the switching element in the switch unit 11 from off to on is changed according to the elapsed time since the pre-charging circuit 1 starts pre-charging the smoothing capacitor 3. th That is, the longer the time elapsed from the start of the preliminary charging of the smoothing capacitor 3, the longer the first predetermined time τ1 is made, or the voltage threshold V thAs a result, the longer the time elapsed from the start of the pre-charging of the smoothing capacitor 3, the longer the on-time of the switching element in the switch unit 11, so that the power flowing from the three-phase AC power supply 5 via the rectifier 2 to the smoothing capacitor 3 can be suppressed from gradually decreasing, and the charging function of the pre-charging circuit 1 for the smoothing capacitor 3 can be maintained.

[0128] In the third changing method, the first predetermined time τ1 or the voltage threshold value V used when the switching element in the switch section 11 is switched from off to on by the control section 13 is changed according to the peak value of each phase current flowing from the three-phase AC power supply 5 to the rectifier during the pre-charging period of the smoothing capacitor 3 of the pre-charging circuit 1. th If the voltage threshold V th If the pre-charging circuit 1 continues to pre-charge while maintaining a fixed value, the difference between the voltage of the smoothing capacitor 3 and the line voltage of the three-phase AC power supply 5 gradually decreases. The peak value of each phase current flowing from the three-phase AC power supply 5 to the rectifier becomes smaller. Therefore, in the third modification method, the peak value of each phase current flowing from the three-phase AC power supply 5 to the rectifier is detected by the current detection circuit 14, and the first predetermined time τ1 is gradually extended or the voltage threshold V is gradually increased. th , in order to maintain the peak value of the detected current.

[0129] In the fourth changing method, the first predetermined time τ1 or the voltage threshold V used when the control unit 13 switches the switch element in the switch unit 11 from off to on is changed at a predetermined fixed increase rate. th That is, the first predetermined time τ1 is extended at a fixed increase rate, or the voltage threshold V is increased at a fixed increase rate. th .

[0130] The embodiments of the present disclosure are described in detail, but the present disclosure is not limited to the above-mentioned embodiments. These embodiments may be subjected to various additions, substitutions, changes, partial deletions, etc. without departing from the scope of the spirit of the invention, or without departing from the scope of the spirit of the invention derived from the contents recorded in the claims and their equivalents. For example, in the above-mentioned embodiments, the order of each action and the order of each processing are shown as an example, but are not limited to this. In addition, the same is true for the case where numerical values ​​or mathematical formulas are used in the description of the above-mentioned embodiments.

[0131] Explanation of symbols

[0132] 1. Prepare charging circuit

[0133] 2 Rectifier

[0134] 3 Smoothing capacitor

[0135] 4 Inverter

[0136] 5 Three-phase AC power supply

[0137] 6 Electric Motor

[0138] 11 Switch

[0139] 12 Power supply voltage detection circuit

[0140] 13. Control Unit

[0141] 14 Current detection circuit

[0142] 15 Capacitor voltage detection circuit

[0143] 100 Motor drive device

[0144] D RL The diode of the lower arm of the R phase

[0145] D SL The diode of the lower arm of the S phase

[0146] D TL The diode of the lower arm of the T phase

[0147] D RU The diode on the upper arm of the R phase

[0148] D SU The diode on the upper arm of the S phase

[0149] D TU The diode on the upper arm of the T phase

[0150] S R R phase switching element

[0151] S S S-phase switching element

[0152] S T T-phase switching element

[0153] S R1 The first R-phase switching element

[0154] S R2 The second R-phase switching element

[0155] S S1 The first S-phase switching element

[0156] S S2 The second S-phase switching element

[0157] S T1 The first T-phase switching element

[0158] S T2The second T-phase switching element.

Claims

1. A pre-charging circuit for pre-charging a smoothing capacitor connected to a DC output side of a rectifier, wherein the rectifier converts input AC power into DC power and outputs the DC power, characterized in that: The preparatory charging circuit comprises: a switch unit having a switch element, which electrically connects the three-phase AC power supply to the AC input side of the rectifier when turned on, and electrically disconnects the three-phase AC power supply from the AC input side of the rectifier when turned off; a power supply voltage detection circuit, which detects the AC voltage of the three-phase AC power supply; and A control unit controls the on and off of the switching element of the switching unit based on information related to the AC voltage detected by the power supply voltage detection circuit.

2. The pre-charging circuit according to claim 1, characterized in that: The pre-charging circuit includes: a current detection circuit that detects each phase current flowing from the three-phase AC power supply to the AC input side of the rectifier; When the current detected by the current detection circuit is an overcurrent, the control unit controls the switching element of the switch unit to turn off, thereby electrically disconnecting the three-phase AC power supply from the AC input side of the rectifier.

3. The preparatory charging circuit according to claim 1 or 2, characterized in that: The switch unit has, for each phase of the three-phase power line between the three-phase AC power supply and the AC input side of the rectifier, a group consisting of a switching element and a diode connected in anti-parallel to the switching element, wherein the switching element conducts the current flowing from the three-phase AC power supply to the AC input side of the rectifier when turned on, and electrically cuts off the connection between the three-phase AC power supply and the AC input side of the rectifier when turned off.

4. The preparatory charging circuit according to claim 3, characterized in that: The control unit determines the phase having the second largest phase voltage among the three-phase phase voltages detected by the power supply voltage detection circuit as the conduction phase, and controls the switching element of the conduction phase to switch from off to on at the following time: a time before the first predetermined time when the magnitude relationship between the phase voltage of the conduction phase and the phase voltage of the smallest phase is reversed; or a time when the line voltage between the conduction phase and the smallest phase becomes less than a predetermined voltage threshold, After the switching element of the conducting phase is turned on, the control unit controls the switching element of the conducting phase to switch from on to off at the following moments: the moment when the current flowing through the switching element of the conducting phase is approximately zero; or the moment when a second specified time has passed since the phase voltage of the conducting phase became the minimum among the three-phase phase voltages.

5. The preparatory charging circuit according to claim 1 or 2, characterized in that: The switch unit has switch elements in two phases of the three-phase power line between the three-phase AC power source and the AC input side of the rectifier, and the switch elements can selectively switch between the following states: Conducting of current flowing in a first conducting direction, wherein the first conducting direction is from the three-phase AC power source when turned on toward the AC input side of the rectifier; Conducting of current flowing in a second conducting direction, wherein the second conducting direction is from the AC input side of the rectifier when turned on toward the three-phase AC power supply; and When disconnected, the electricity between the three-phase AC power supply and the AC input side of the rectifier is cut off.

6. The preparatory charging circuit according to claim 5, characterized in that: The control unit controls the switching element of the phase where the line voltage switches from positive to negative to switch from off to on so that the first conduction direction is turned on, and controls the switching element of the phase where the line voltage switches from negative to positive to switch from off to on so that the second conduction direction is turned on, wherein: The time is: a time before the first predetermined time when the magnitude relationship between the phase with the switching element and the phase without the switching element in the three-phase phase voltage detected by the power supply voltage detection circuit is reversed; or a time when the line voltage between the three phases detected by the power supply voltage detection circuit becomes less than a predetermined voltage threshold, The line voltage is a voltage between a phase having the switching element and a phase not having the switching element, detected by the power supply voltage detection circuit. After the switching element is turned on, the control unit controls the switching element to switch from on to off at the following moments: the moment when the current flowing through the turned-on switching element is substantially zero; or the moment when a second prescribed time has passed since the line voltage switched from positive to negative and from negative to positive.

7. The preparatory charging circuit according to claim 1 or 2, characterized in that: The switch unit has a switch element on the three-phase power line between the three-phase AC power source and the AC input side of the rectifier, and the switch element can selectively switch the following states: Conducting of current flowing in a first conducting direction, wherein the first conducting direction is from the three-phase AC power source when turned on toward the AC input side of the rectifier; Conducting of current flowing in a second conducting direction, wherein the second conducting direction is from the AC input side of the rectifier when turned on toward the three-phase AC power supply; and When disconnected, the electricity between the three-phase AC power supply and the AC input side of the rectifier is cut off.

8. The preparatory charging circuit according to claim 7, characterized in that: The control unit controls the switching element of the phase where the three-phase line voltage detected by the power supply voltage detection circuit switches from positive to negative to switch from off to on so as to conduct the current flowing in the first conduction direction, and controls the switching element of the phase where the three-phase line voltage detected by the power supply voltage detection circuit switches from negative to positive to switch from off to on so as to conduct the current flowing in the second conduction direction, wherein: The time is: a time that is a first predetermined time earlier than the time when the magnitude relationship of the three-phase phase voltage detected by the power supply voltage detection circuit is reversed; or a time when the three-phase line voltage detected by the power supply voltage detection circuit becomes less than a predetermined voltage threshold, After the switching element is turned on, the control unit controls the switching element to switch from on to off at the following moments: the moment when the current flowing through the turned-on switching element is substantially zero; or the moment when a second prescribed time has passed since the line voltage switched from positive to negative and from negative to positive.

9. The preparatory charging circuit according to claim 4 or 8, characterized in that: The first predetermined time or the voltage threshold used when the control unit switches the switching element from off to on is changed according to the voltage of the smoothing capacitor.

10. The preparatory charging circuit according to claim 9, characterized in that: As the voltage of the smoothing capacitor increases, the first predetermined time used when the control unit switches the switching element from off to on is lengthened or the voltage threshold is increased.

11. The preparatory charging circuit according to claim 4 or 8, characterized in that: The first predetermined time or the voltage threshold used when the control unit switches the switching element from off to on is changed according to an elapsed time from the start of pre-charging of the smoothing capacitor.

12. The preparatory charging circuit according to claim 11, characterized in that: The longer the elapsed time from the start of pre-charging of the smoothing capacitor, the longer the first predetermined time used when the control unit switches the switching element from off to on is or the larger the voltage threshold is.

13. The preparatory charging circuit according to claim 4 or 8, characterized in that: The first predetermined time or the voltage threshold used when the control unit switches the switching element from off to on is changed according to the peak value of each phase current flowing from the three-phase AC power supply to the AC input side of the rectifier during the preparatory charging period of the smoothing capacitor.

14. The preparatory charging circuit according to claim 4 or 8, characterized in that: The first predetermined time used when the control unit switches the switching element from off to on is gradually increased at a fixed increase rate, or the voltage threshold is gradually increased at a fixed increase rate.

15. A motor driving device, characterized in that: have: The preparatory charging circuit according to any one of claims 1 to 14; the rectifier; the smoothing capacitor; and The inverter converts the DC power into AC power for driving the motor and outputs the AC power.

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