Drive unit and air conditioning device

Abstract

A drive device (100) includes: a converter (3) that rectifies AC voltage supplied from an AC power supply (2); an inverter (4) that generates, from the rectified voltage obtained by the converter (3) AC voltage corresponding to a set rotational speed, and supplies said AV voltage to an electric motor (1); a connection switching device (20) that switches a connection state of a wiring of the electric motor (1) in accordance with a switching command; and a control unit (30). The control unit (30): estimates, after a first connection is selected by the connection switching device (30), secondary magnetic flux before switching; determines a demagnetization level by comparing the estimated value of the secondary magnetic flux before switching and a predetermined induced voltage constant in a first connection state; estimates, after switching to a second connection by the connection switching device (20) is performed, a secondary magnetic flux after switching; and performs a determination of connection switching success or failure by comparing the estimated value of the secondary magnetic flux after switching and a value obtained by correcting on the basis of the demagnetization level a predetermined induced voltage constant in a second connection state.

Description

[Technical field]

[0001] The present disclosure relates to a drive device that drives an electric motor whose connection state can be switched by an inverter, and an air conditioner having the drive device. [Background technology]

[0002] Conventionally, there is known a driving device having a connection switching device that switches the stator windings of an electric motor to one of a plurality of different connection states, and that is capable of switching the winding connections while the electric motor is in operation. For example, there is known a driving device that switches the windings of an electric motor when the current is zero, and determines whether to switch the windings by comparing the values ​​of the induced voltage and the speed before and after the switching (see, for example, Patent Document 1). Patent Document 2 discloses a method of estimating magnetic flux information including the induced voltage and secondary magnetic flux using an adaptive observer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-148490 A [Patent Document 2] International Publication No. 2002 / 091558 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, in order to check whether the connection switching was performed correctly, the success or failure of the connection switching is judged by comparing the values ​​equivalent to the induced voltage constant before and after the connection switching. If the compressor motor is a permanent magnet type motor and the motor is demagnetized, the conventional technology has a problem in that it is difficult to judge the switching because the induced voltage constant becomes a value smaller than the expected value.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide a drive device that can appropriately determine whether connection switching has been successful, regardless of the demagnetization level of the motor. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the object, a drive device according to the present disclosure includes a converter that rectifies an AC voltage supplied from an AC power source, an inverter that generates an AC voltage corresponding to a set rotation speed from the rectified voltage obtained by the converter and supplies the AC voltage to an electric motor, a connection switching device that switches the connection state of the windings of the electric motor according to a switching command, a detection unit that detects a load current of the electric motor, and a control unit that controls the inverter and the connection switching device. After the connection switching device selects a first connection, the control unit estimates a secondary magnetic flux before switching and determines a demagnetization level by comparing an estimated value of the secondary magnetic flux before switching with a preset induced voltage constant in the first connection state, and after the connection switching device switches to the second connection, the control unit estimates a secondary magnetic flux after switching and determines whether the connection switching has been successful by comparing an estimated value of the secondary magnetic flux after switching with a value obtained by correcting the preset induced voltage constant in the second connection state based on the demagnetization level. Effect of the Invention

[0007] The drive device according to the present disclosure has the advantage of being able to appropriately determine whether or not connection switching has been successful, regardless of the demagnetization level of the motor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of a drive device according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing in detail the windings of a stator of an electric motor and a connection switching device according to a first embodiment. [Diagram 3] A wiring diagram showing details of a switch of a connection switching device included in a drive device according to the first embodiment. [Figure 4] A conceptual diagram showing the connection of the stator windings when the motor is connected in Y-connection [Diagram 5] A diagram conceptually showing the connection state of the stator windings when the motor is connected in delta connection. [Figure 6] FIG. 1 is a diagram showing a configuration of a control unit included in a drive device according to a first embodiment; [Figure 7] FIG. 1 is a diagram for explaining a control sequence when switching wiring in the first embodiment. [Figure 8] FIG. 13 is a diagram showing the configuration of an air conditioning device according to a second embodiment. [Figure 9] FIG. 1 is a diagram showing a processor in a case where a part or all of a control unit included in a drive device according to a first embodiment is realized by a processor. [Figure 10] FIG. 1 is a diagram showing a processing circuit in the case where a part or all of a control unit included in a driving device according to a first embodiment is realized by the processing circuit; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A drive device and an air conditioner according to an embodiment will be described in detail below with reference to the drawings.

[0010] Embodiment 1 Fig. 1 is a diagram showing the configuration of a driving device 100 according to embodiment 1. The driving device 100 is a device that drives an electric motor 1 connected to a load 5, and includes a converter 3, an inverter 4, a connection switching device 20, and a control unit 30. Fig. 1 also shows the electric motor 1, an AC power source 2, and the load 5.

[0011] The converter 3 receives an AC voltage supplied from the AC power source 2, rectifies the AC voltage, and outputs a DC voltage. Hereinafter, the DC voltage output from the converter 3 may be referred to as a "bus voltage." The converter 3 may be a converter that performs rectification using a diode bridge, or may be a boost converter that can increase the bus voltage using a reactor and a switching element controlled by the control unit 30.

[0012] The inverter 4 is controlled by the control unit 30, and generates an AC voltage corresponding to a set rotation speed from the rectified voltage obtained by the converter 3, and supplies the AC voltage to the electric motor 1. More specifically, the inverter 4 converts the DC voltage output from the converter 3 into an AC voltage whose voltage and frequency are variable, and drives the electric motor 1. The control unit 30 controls the inverter 4 based on the load current to the electric motor 1 output by the inverter 4. The driving device 100 further includes detection units 6a and 6b that detect the load current of the electric motor 1. The detection units 6a and 6b may be current sensors such as a known ACCT (Alternating Current Transformer) or DCCT (Direct Current Transformer) that directly detect the load current of the electric motor 1 as shown in FIG. 1, or may be components that detect a bus current flowing between the converter 3 and the inverter 4 and estimate the load current of the electric motor 1 as shown in FIG. 6 described later. The detection method or estimation method performed by the detection units 6a and 6b is not limited. The control unit 30 receives information on the load current detected by the detection units 6a and 6b.

[0013] The motor 1 is a three-phase synchronous motor, and the ends of the stator windings are pulled out to the outside of the motor 1. The windings of the motor 1 can be either Y-connected or Δ-connected. The Y-connection is a star connection, and the Δ-connection is a delta connection. The connection switching device 20 switches the connection state of the windings of the motor 1 according to a switching command. In other words, the connection switching device 20 selects the connection of the motor 1. The connection switching device 20 has switches 21, 22, and 23. The control unit 30 controls whether the motor 1 is driven with the Y-connection or the Δ-connection.

[0014] 2 is a diagram showing in detail the windings of the stator of the electric motor 1 and the connection switching device 20 according to the first embodiment. As shown in FIG. 2, the first ends 41a, 42a, 43a of the three-phase windings 41, 42, 43 consisting of the U-phase, V-phase, and W-phase of the electric motor 1 are connected to the external terminals 41c, 42c, 43c of the drive device 100. Specifically, the first end 41a is connected to the external terminal 41c of the drive device 100, the first end 42a is connected to the external terminal 42c of the drive device 100, and the first end 43a is connected to the external terminal 43c of the drive device 100. The first ends 41a, 42a, 43a are also connected to the U-phase, V-phase, and W-phase outputs of the inverter 4.

[0015] The second ends 41b, 42b, 43b of the three phase windings 41, 42, 43 of the electric motor 1 are connected to external terminals 41d, 42d, 43d of the drive device 100. Specifically, the second end 41b is connected to the external terminal 41d of the drive device 100, the second end 42b is connected to the external terminal 42d of the drive device 100, and the second end 43b is connected to the external terminal 43d of the drive device 100. The external terminals 41c, 42c, 43c, 41d, 42d, 43d are connected to the connection switching device 20.

[0016] The connection switching device 20 has the switches 21, 22, and 23 as described above. The switch 21 receives a current flowing through the winding 41, the switch 22 receives a current flowing through the winding 42, and the switch 23 receives a current flowing through the winding 43. The switch 21 has a function of switching the path of the current flowing through the winding 41, the switch 22 has a function of switching the path of the current flowing through the winding 42, and the switch 23 has a function of switching the path of the current flowing through the winding 43. The switches 21, 22, and 23 are electromagnetic contactors whose contacts are electromagnetically opened and closed. The electromagnetic contactors include components called relays and contactors. The configuration of the electromagnetic contactors is, for example, as shown in FIG. 3, and the electromagnetic contactors are in different connection states when a current is flowing through the exciting coils 211, 221, and 231 and when a current is not flowing through them.

[0017] 3 is a wiring diagram showing the details of the switches 21, 22, and 23 of the connection switching device 20 of the driving device 100 according to the first embodiment. For the excitation coils 211, 221, and 231, the connection state between the excitation coils 211, 221, and 231 and the power source 25 is switched by the semiconductor switch 204 controlled by the connection selection signal Sc output from the control unit 30, and the presence or absence of a current is also switched. For example, when the connection selection signal Sc indicates a first value, the semiconductor switch 204 is turned off, and no current flows through the excitation coils 211, 221, and 231, and when the connection selection signal Sc indicates a second value, the semiconductor switch 204 is turned on, and a current flows through the excitation coils 211, 221, and 231. The first value is, for example, Low, and the second value is, for example, High. When the connection selection signal Sc is output from a circuit having a sufficient current capacity, the exciting coils 211, 221, and 231 may be driven directly by the connection selection signal Sc without going through the semiconductor switch 204.

[0018] With respect to the switch 21, the common contact 21c is connected to an external terminal 41d via a lead wire, the normally closed contact 21b is connected to the neutral node 24, and the normally open contact 21a is connected to the W-phase output of the inverter 4. With respect to the switch 22, the common contact 22c is connected to an external terminal 42d via a lead wire, the normally closed contact 22b is connected to the neutral node 24, and the normally open contact 22a is connected to the V-phase output of the inverter 4. With respect to the switch 23, the common contact 23c is connected to an external terminal 43d via a lead wire, the normally closed contact 23b is connected to the neutral node 24, and the normally open contact 23a is connected to the U-phase output of the inverter 4.

[0019] When no current flows through the excitation coils 211, 221, 231, the switches 21, 22, 23 are switched to the normally closed contacts 21b, 22b, 23b, i.e., the common contacts 21c, 22c, 23c are connected to the normally closed contacts 21b, 22b, 23b, as shown in Fig. 3. In this state, the second ends 41b, 42b, 43b of the windings 41, 42, 43 are connected at the neutral node 24 via the switches 21, 22, 23. Therefore, the connection state of the motor 1 is a Y connection state.

[0020] When current flows through the excitation coils 211, 221, and 231, the switches 21, 22, and 23 are switched to the normally open contacts 21a, 22a, and 23a, i.e., the common contacts 21c, 22c, and 23c are connected to the normally open contacts 21a, 22a, and 23a, in contrast to the case shown in Fig. 3. In this state, the second ends 41b, 42b, and 43b of the windings 41, 42, and 43 are connected to the first ends 42a, 43a, and 41a of the windings 43, 42, and 41 through the switches 21, 22, and 23. Therefore, the connection state of the electric motor 1 is a Δ connection state.

[0021] As described above, when the connection selection signal Sc indicates a first value, for example, Low, the motor 1 is in a Y-connection state, and when the connection selection signal Sc indicates a second value, for example, High, the motor 1 is in a Δ-connection state.

[0022] The advantages of the configuration in which the electric motor 1 can be switched between Y-connection and Δ-connection will be described below with reference to Fig. 4 and Fig. 5. Fig. 4 is a conceptual diagram showing the connection state of the stator windings when the electric motor 1 is connected in Y-connection. Fig. 5 is a conceptual diagram showing the connection state of the stator windings when the electric motor 1 is connected in Δ-connection.

[0023] The line voltage in Y connection is V Y , the current flowing in is I Y The line voltage in the Δ connection is V Δ , the current flowing in is I Δ If we assume that the voltage applied to each phase winding is equal, then V Δ=V Y / √3 ···(1) The following relationship holds: I Δ =√3×I Y (2) It is well known that the following relationship can be obtained.

[0024] Voltage V when wired in Y-connection Y and current I Y and the voltage V when connected in delta Δ and current I Δ When the relationship between equations (1) and (2) is satisfied, the power supplied to the motor 1 is equal between Y-connection and Δ-connection. In other words, when the power supplied to the motor 1 is equal between Y-connection and Δ-connection, the current is larger and the voltage required to drive it is lower in the Δ-connection. The difference between Y-connection and Δ-connection is also reflected in the motor constants; when the motor 1 is a three-phase synchronous motor, the induced voltage constant φa is the effective value of the armature flux linkage of the permanent magnet, and ideally the relationship in equation (3) holds. φ aY =√3×φ aΔ (3) φ aY is the induced voltage constant in Y connection, and φ aΔ is the induced voltage constant in the delta connection. The allowable current of the motor 1 also differs between the Y connection and the delta connection, and is larger in the delta connection.

[0025] When a synchronous motor is used, as the rotation speed increases, that is, as the load increases, the back electromotive force increases and the voltage required to drive the motor increases. As mentioned above, this electromotive force is larger in the Y connection than in the Delta connection.

[0026] In order to suppress the back electromotive force at high speeds, it is possible to reduce the magnetic force of the permanent magnets or the number of turns of the stator windings, but doing so would increase the current required to obtain the same output torque, which would increase the current flowing through the motor 1 and inverter 4, reducing the efficiency of driving the motor 1.

[0027] Therefore, it is possible to switch the connections according to the rotation speed. For example, when high speed rotation is required, a delta connection is used. By doing so, the voltage required for driving can be reduced to 1 / √3 of that required for Y connection. Furthermore, there is no need to reduce the number of turns in the windings, so the efficiency of driving the motor 1 does not decrease. Note that high speed rotation corresponds to a large load.

[0028] On the other hand, at low speeds, by using a Y connection for the motor 1, the current value can be reduced to 1 / √3 of that when using a Δ connection. Furthermore, it is possible to design the number of turns with a Y connection to be suitable for driving at low speeds, and since the current value can be reduced compared to when a Y connection is used across the entire speed range, it is possible to increase the efficiency of driving the motor 1. Note that low speeds correspond to small loads.

[0029] From the above, if the wiring can be switched according to the rotation speed, i.e., the load conditions, it is possible to improve efficiency at low loads and also to increase output at high loads.

[0030] The control unit 30 controls the inverter 4 and the connection switching device 20. The control unit 30 controls the inverter 4 to change the frequency and voltage value of the output voltage from the inverter 4. The control unit 30 controls the connection switching device 20 to select the connection of the motor 1. If the converter 3 is a boost converter, the control unit 30 also controls the boost converter to change the bus voltage.

[0031] Fig. 6 is a diagram showing the configuration of the control unit 30 included in the drive device 100 according to the embodiment 1. Fig. 6 shows all the components included in the drive device 100, the electric motor 1, the AC power source 2, and the load 5. As shown in Fig. 6, the control unit 30 has an operation command unit 31 and an inverter control unit 32, and when the converter 3 is a boost converter, it also has a control unit for controlling the boost converter.

[0032] The operation command unit 31 determines a frequency command value ω * , a zero selection signal Sz, and a connection selection signal Sc are output.* The zero selection signal Sz is supplied to the inverter control unit 32. * is set to a value suitable for the operating state. If the converter 3 is a boost converter, the bus voltage command value is set to a value suitable for the operating state, and the bus is boosted to an arbitrary value. The inverter control unit 32 outputs a PWM (Pulse Width Modulation) signal Sm that controls the switching operation of the inverter 4 to the inverter 4, and changes the frequency and voltage value of the output voltage of the inverter 4.

[0033] The connection selection signal Sc indicates a first value, for example, Low, when the Y connection is selected, and indicates a second value, for example, High, when the Δ connection is selected.

[0034] The zero selection signal Sz normally indicates a first value, for example, Low, and indicates a second value, for example, High, during a period of zero current control described later.

[0035] The operation command unit 31 determines, for example, whether the stator winding of the motor 1 is to be Y-connected or Δ-connected, determines the target rotation speed, and judges whether the connection switching has been successful. Based on the determination, the operation command unit 31 outputs a connection selection signal Sc and a frequency command value ω * and outputs an inverter stop signal So. When there is no abnormality in the connection state, the inverter stop signal So normally indicates a first value, for example, Low, and when it is determined that the switching has failed in a connection switching success / failure determination described below, it indicates a second value, for example, High.

[0036] For example, when the load 5 connected to the motor 1 is an air conditioner, the operation command unit 31 determines that the connection of the motor 1 is a Δ connection when the difference between the room temperature and the set temperature is large, sets the connection selection signal Sc to a second value, for example, a signal indicating High, sets the target rotation speed to a relatively high value, and sets a frequency command value ω that gradually increases the frequency to a frequency corresponding to the target rotation speed after startup. *When the frequency reaches a frequency corresponding to the target rotation speed, the operation command unit 31 maintains the state until the room temperature approaches the set temperature, and when the room temperature approaches the set temperature, the operation command unit 31 sets the connection selection signal Sc to a first value, for example, a signal indicating Low, in order to switch the connection of the electric motor 1 to a Y connection, and then performs control to maintain the room temperature close to the set temperature. This control includes adjusting the frequency, and stopping and restarting the electric motor 1, etc.

[0037] When the motor 1 is a three-phase synchronous motor, ideally the induced voltage constant φa and the secondary magnetic flux φdr have the same value, so the connection state can be determined based on the change in the estimated value of the secondary magnetic flux φdr. However, demagnetization or magnetization occurs due to the temperature dependency of the permanent magnet. For example, if the permanent magnet constituting the motor 1 is a magnet that demagnetizes at high temperatures, irreversible demagnetization occurs when the temperature exceeds a certain level, in which the magnetic force does not return to its original state, and the performance of the motor 1 is significantly reduced. In addition, since the value of the induced voltage constant φa changes before and after the connection switching, it is necessary to clearly distinguish between the phenomenon caused by the connection switching and the effect of demagnetization in the change in the estimated value of the secondary magnetic flux φdr before and after the connection switching, and then determine the state of the connection switching.

[0038] To determine whether the connection switching is successful, first, an induced voltage constant φa in a first connection state before the connection switching and an induced voltage constant φa in a second connection state after the connection switching are preset. For example, the set value of the induced voltage constant φa may be a design value used when the motor 1 is designed. The control unit 30 estimates the secondary magnetic flux φdr before the connection switching. As a method for estimating the secondary magnetic flux φdr, as described above, Patent Document 2 discloses a method for estimating magnetic flux information including the induced voltage and the secondary magnetic flux φdr using an adaptive observer. The control unit 30 estimates the secondary magnetic flux φdr by using a method similar to the method.

[0039] The control unit 30 compares the estimated value of the secondary magnetic flux φdr with a preset induced voltage constant φa in the first connection state, thereby calculating the demagnetization level based on the following equation (4). Demagnetization level value (%) = Estimated secondary magnetic flux φdr / Induced voltage constant φa × 100 (4)

[0040] When the control unit 30 determines whether the connection switching has been successful after the connection switching, it estimates the value of the secondary magnetic flux φdr after the connection switching, and when it determines whether the connection switching has been successful by comparing the induced voltage constant φa after the connection switching, i.e., in the second connection state, with the demagnetization level, it makes the determination taking into account the demagnetization level obtained by equation (4).

[0041] After the connection switching operation is performed, the control unit 30 re-estimates the secondary magnetic flux φdr after the connection switching, and compares the estimated value of the secondary magnetic flux φdr with a preset induced voltage constant φa in the second connection state after the connection switching to determine whether the connection switching was successful. Specifically, a determination value K is set, and the control unit 30 compares the correction calculation result of the following correction formula (5) with the determination value K, and determines that the switching is normal if the calculation result falls below the absolute value of the determination value K. (Estimated value of secondary magnetic flux φdr) - (Induced voltage constant φa × Demagnetization level value (%) / 100) (5)

[0042] In determining the judgment value K, the control unit 30 considers variations in control convergence after the switching of the connection that affects the estimated value of the secondary magnetic flux φdr in addition to the influence of demagnetization, and performs the judgment by giving positive and negative likelihood to the judgment value K. More specifically, when the control unit 30 judges whether the connection switching is successful or not, it judges whether the connection switching is successful or not by giving positive and negative likelihood to the judgment value K when comparing the estimated value of the secondary magnetic flux φdr after the switching with a value obtained by correcting the preset induced voltage constant φa in the second connection state based on the demagnetization level. This makes it possible for the drive device 100 to prevent a judgment that the switching has failed even though the switching has been performed normally.

[0043] If the control unit 30 determines that the switching has failed in the connection switching success / failure determination, it sets the inverter stop signal So to a signal indicating a second value, for example, High, to make the PWM signal Sm inactive and stop the motor 1. Furthermore, if the control unit 30 determines that the switching state is abnormal as a result of the connection switching success / failure determination, it performs an operation to stop the motor 1.

[0044] Next, the connection switching operation will be described in detail.

[0045] The operation command unit 31 changes the value of the connection selection signal Sc to switch from one of the Y connection and the Δ connection to the other, and temporarily changes the value of the zero selection signal Sz during the connection switching operation.

[0046] For example, when switching the connection, the operation command unit 31 temporarily changes the zero selection signal Sz, which normally indicates Low, to a signal indicating High. During a period in which the zero selection signal Sz indicates High, the operation command unit 31 switches the connection selection signal Sc from a signal indicating High to a signal indicating Low, or from a signal indicating Low to a signal indicating High.

[0047] In order to control the inverter 4, the inverter control unit 32 generates a PWM signal Sm based on information supplied from a detection unit that detects the load current of the electric motor 1 and supplies the PWM signal Sm to the inverter 4. The inverter 4 to which the PWM signal Sm is supplied changes the output voltage value and frequency in accordance with the PWM signal Sm to drive the electric motor 1. Note that Fig. 6 shows an example in which the load current of the electric motor 1 is estimated from information on the bus current Idc.

[0048] Hereinafter, the operation of the driving device 100 when the connection switching device 20 is operated while the electric motor 1 is in operation will be described.

[0049] When the motor 1 is in operation, that is, when current flows through the switches 21, 22, and 23 constituting the connection switching device 20, if the current flowing through the excitation coils 211, 221, and 231 is manipulated, specifically, when the excitation coils 211, 221, and 231 are switched from off to on or from on to off, the connection of the common contacts 21c, 22c, and 23c is switched to the normally closed contacts 21b, 22b, and 23b or the normally open contacts 21a, 22a, and 23a. If power supply from the inverter 4 to the motor 1 continues when the switching occurs, an arc discharge occurs between the contacts of the switches 21, 22, and 23, which may cause the contacts to weld.

[0050] However, if the rotation speed of the motor 1 is set to zero, the torque required for restarting increases, and the current required for starting the motor 1 increases, or the motor 1 may not be able to restart. For example, if the motor 1 serves as a load for a compressor of an air conditioner, the torque required for restarting increases immediately after the rotation speed of the motor 1 is set to zero to drive the compressor, because the state of the refrigerant is not stable. It is also possible to restart the motor 1 after a period of time has elapsed for the state of the refrigerant to be sufficiently stabilized after the rotation speed of the motor 1 is set to zero. In that case, the compressor will not be able to pressurize the refrigerant, and the cooling or heating capacity will decrease, and the room temperature may deviate significantly from the desired temperature.

[0051] By controlling the current flowing through the connection switching device 20 to zero and having the connection switching device 20 perform switching operation in this state, it is possible to prevent arc discharge from occurring between the contacts of the switches 21, 22, and 23 during switching. In this way, it is no longer necessary to set the rotation speed of the motor 1 to zero for switching.

[0052] In order to make the current flowing through the connection switching device 20 zero, there is a method of detecting the current flowing through the motor 1 and controlling the current to zero by the switching operation of the inverter 4. Alternatively, there is a method of cutting off the current by stopping the switching operation of the inverter 4. Alternatively, by using both of these methods in combination, it is possible to make the current flowing through the connection switching device 20 zero.

[0053] Fig. 7 is a diagram for explaining a control sequence when the connection is switched in the first embodiment. In Fig. 7, switching from Y connection to Δ connection is assumed. Fig. 7(A) shows the current flowing through the connection switching device 20. Fig. 7(B) shows a time chart of the zero selection signal Sz. Fig. 7(C) shows a time chart of the connection selection signal Sc. Fig. 7(D) shows an estimated value of the secondary magnetic flux φdr and an induced voltage constant φa.

[0054] Before the zero selection signal Sz changes from a signal indicating Low to a signal indicating High, the control unit 30 estimates the secondary magnetic flux φdr before switching and calculates the demagnetization level of the motor 1. If the secondary magnetic flux φdr is estimated immediately after the switching of the connections, an erroneous estimation may be performed due to the time constant of the control response until control becomes stable when current is passed through the motor 1 again after the switching of the connections and the convergence speed of the estimation of the secondary magnetic flux φdr. Therefore, after the estimated value of the secondary magnetic flux φdr becomes stable, that is, after a preset time has elapsed since the switching of the connections, the control unit 30 re-estimates the secondary magnetic flux φdr and determines whether the switching of the connections has been successful.

[0055] By doing so, the control unit 30 can prevent determining that the wiring switch has failed even though it was performed normally, or that the switching was performed normally even though it was unsuccessful.

[0056] 7, switching from a Y connection to a Δ connection is assumed, but switching from a Δ connection to a Y connection is also performed in the same way. However, when switching from a Δ connection to a Y connection is performed, the content of the connection selection signal Sc in FIG. 7(C) switches from High to Low, not from Low to High.

[0057] As described above, the control unit 30 of the drive device 100 according to the first embodiment estimates the secondary magnetic flux before switching after the first connection is selected by the connection switching device 20, and judges the demagnetization level by comparing the estimated value of the secondary magnetic flux before switching with the induced voltage constant preset in the state of the first connection, and estimates the secondary magnetic flux after switching after the connection switching device 20 switches to the second connection, and judges whether the connection switching is successful by comparing the estimated value of the secondary magnetic flux after switching with the value obtained by correcting the induced voltage constant preset in the state of the second connection based on the demagnetization level. Therefore, the drive device 100 can appropriately judge whether the connection switching is successful regardless of the demagnetization level of the motor 1 by comparing the estimated value of the secondary magnetic flux φdr after the connection switching with the value obtained by correcting the induced voltage constant φa in the state after the connection switching that is preset based on the demagnetization level.

[0058] Embodiment 2 Fig. 8 is a diagram showing the configuration of an air conditioner 200 according to embodiment 2. The air conditioner 200 has the drive unit 100 described in embodiment 1. In embodiment 2, the drive unit 100 drives the electric motor 1 that drives a compressor 904 included in the air conditioner 200. In other words, the air conditioner 200 has the electric motor 1 that is driven by the drive unit 100. The air conditioner 200 further has a compressor 904 that compresses a refrigerant in a refrigeration cycle 900 using the electric motor 1 as a drive source.

[0059] The refrigeration cycle 900 can perform heating operation or cooling operation by switching the four-way valve 902. During heating operation, as indicated by the solid arrow, the refrigerant is pressurized by the compressor 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910, and the four-way valve 902, and returns to the compressor 904. During cooling operation, as indicated by the dashed arrow, the refrigerant is pressurized by the compressor 904 and sent out, passes through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906, and the four-way valve 902, and returns to the compressor 904.

[0060] A driving device 100 connected to an AC power source 2 performs variable speed control to drive an electric motor 1, and the electric motor 1 drives a compressor 904. During heating operation, the indoor heat exchanger 906 functions as a condenser, and the outdoor heat exchanger 910 functions as an evaporator. During cooling operation, the outdoor heat exchanger 910 functions as a condenser, and the indoor heat exchanger 906 functions as an evaporator to absorb heat. An expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0061] Depending on the degree of indoor temperature adjustment, the pressure ratio of the compressor 904 varies, and when the indoor set temperature and the indoor actual temperature are significantly different, the driving device 100 increases the rotation speed of the motor 1 to create a high compression state.

[0062] As described above, the air conditioning apparatus 200 according to the second embodiment has the drive unit 100 described in the first embodiment, and therefore can switch the connections of the motor 1 in response to the drive status without stopping the compressor 904, and can therefore continue the air conditioning operation. In other words, the air conditioning apparatus 200 can improve the comfort of the user. Furthermore, because the success / failure of the connection switching is correctly determined, the air conditioning apparatus 200 can stop the inverter 4 of the drive unit 100 when an abnormality occurs in the switching of the connection, and can prevent the air conditioning apparatus 200 from continuing operation in a state where the connection is abnormal.

[0063] Fig. 9 is a diagram showing a processor 91 in the case where a part or all of the control unit 30 included in the driving device 100 according to the first embodiment is realized by the processor 91. In other words, a part or all of the functions of the control unit 30 may be realized by the processor 91 that executes a program stored in a memory 92. The processor 91 is a CPU (Central Processing Unit), a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor). The memory 92 is also shown in Fig. 9.

[0064] When some or all of the functions of the control unit 30 are realized by the processor 91, the functions are realized by the processor 91 and software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 92. The processor 91 realizes some or all of the functions of the control unit 30 by reading and executing the program stored in the memory 92.

[0065] When some or all of the functions of the control unit 30 are realized by the processor 91, the drive device 100 has a memory 92 for storing a program that results in some or all of the steps executed by the control unit 30. It can also be said that the program stored in the memory 92 causes a computer to execute at least a portion of the procedure or method executed by the control unit 30.

[0066] The memory 92 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disk).

[0067] 10 is a diagram showing a processing circuit 93 in a case where a part or all of the control unit 30 included in the driving device 100 according to the first embodiment is realized by the processing circuit 93. In other words, a part or all of the control unit 30 may be realized by the processing circuit 93.

[0068] The processing circuit 93 is dedicated hardware, and may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0069] A portion of the control unit 30 may be realized by dedicated hardware separate from the remainder of the control unit 30.

[0070] Some of the functions of the control unit 30 may be realized by software or firmware, and the remaining functions may be realized by dedicated hardware. In this way, the functions of the control unit 30 can be realized by hardware, software, firmware, or a combination of these.

[0071] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0072] 1 electric motor, 2 AC power source, 3 converter, 4 inverter, 5 load, 6a, 6b detection unit, 20 connection switching device, 21, 22, 23 switch, 21a, 22a, 23a normally open contact, 21b, 22b, 23b normally closed contact, 21c, 22c, 23c common contact, 24 neutral node, 25 power source, 30 control unit, 31 operation command unit, 32 inverter control unit, 41, 42, 43 winding, 41a, 42a, 43a first end, 41b, 42b, 43b second end, 41c, 41d, 42c, 42d, 43c, 43d external terminal, 91 processor, 92 memory, 93 processing circuit, 100 drive unit, 200 air conditioning device, 204 Semiconductor switch, 211, 221, 231 Excitation coil, 900 Refrigeration cycle, 902 Four-way valve, 904 Compressor, 906 Indoor heat exchanger, 908 Expansion valve, 910 Outdoor heat exchanger.

Claims

1. A converter that rectifies an AC voltage supplied from an AC power source; an inverter that generates an AC voltage corresponding to a set rotation speed from the rectified voltage obtained by the converter and supplies the AC voltage to an electric motor; a connection switching device that switches a connection state of the windings of the motor in accordance with a switching command; A detection unit that detects a load current of the electric motor; a control unit for controlling the inverter and the connection switching device, The control unit, after the first connection is selected by the connection switching device, estimates a secondary magnetic flux before switching and determines a demagnetization level by comparing the estimated value of the secondary magnetic flux before switching with a preset induced voltage constant in the state of the first connection, and, after switching to the second connection is performed by the connection switching device, estimates a secondary magnetic flux after switching and determines whether the connection switching has been successful by comparing the estimated value of the secondary magnetic flux after switching with a value obtained by correcting the preset induced voltage constant in the state of the second connection based on the demagnetization level. Drive unit.

2. The control unit determines that the switching is normal if the correction calculation result of the following formula is below the absolute value of the judgment value: (Estimated value of secondary magnetic flux) - (Induced voltage constant x Demagnetization level value (%) / 100) The drive device according to claim 1 .

3. When the control unit determines that the switching state is abnormal as a result of the connection switching success / failure determination, the control unit performs an operation to stop the electric motor.

3. A drive device according to claim 1 or 2.

4. The control unit determines whether the wiring connection switching is successful or not after a preset time has elapsed since the wiring connection switching is performed. A drive device according to any one of claims 1 to 3.

5. An electric motor driven by the drive device according to any one of claims 1 to 4; a compressor that compresses a refrigerant in a refrigeration cycle using the electric motor as a drive source; An air conditioning device comprising:

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