Winding switching device and winding switching system

Abstract

According to the present invention, a winding switching device for switching the connection states of a plurality of windings of a motor capable of switching the connection states of the plurality of windings between a first connection state and a second connection state, comprises: a detection unit that detects a zero-crossing point of a measurement value of a current sensor that measures the current flowing through the winding; and a switching unit that switches the connection states of the plurality of windings between the first connection state and the second connection state at a timing when the detection unit detects the zero-crossing point.

Description

Winding switching device and winding switching system

[0001] This application claims priority to Japanese Patent Application No. 2022-109213, filed on July 6, 2022, and incorporates by reference the entire content of that application.

[0002] For example, some motors mounted on electric vehicles can switch between a low-speed, high-torque operating state and a high-speed, low-torque operating state by switching the connections of multiple windings. Patent Document 1 discloses a device that identifies a period during which the AC motor current is below a predetermined value and switches the windings during the identified period in order to prevent surge voltages.

[0003] Japanese Patent Application Laid-Open No. 2020-072632

[0004] A winding switching device according to one aspect of the present disclosure is a winding switching device for switching the connection states of multiple windings of a motor that can switch the connection states of the multiple windings between a first connection state and a second connection state, and includes: a detection unit that detects a zero-cross point of a measurement value of a current sensor that measures a current flowing through the windings; and a switching unit that switches the connection states of the multiple windings between the first connection state and the second connection state at the timing when the detection unit detects the zero-cross point.

[0005] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to a first embodiment. FIG. 2 is a circuit diagram showing an example of the configuration of a winding switching device according to the first embodiment. FIG. 3 is a circuit diagram showing an example of the configuration of a control circuit. FIG. 4 is a timing chart showing an example of transitions in the states of signals in the winding switching device according to the first embodiment. FIG. 5 is a circuit diagram showing an example of the configuration of a winding switching device according to a second embodiment. FIG. 6 is a circuit diagram showing an example of the configuration of a winding switching device according to a third embodiment. FIG. 7 is a circuit diagram showing an example of the configuration of a correction circuit. FIG. 8A is a graph showing waveforms of a voltage signal from a current sensor and a voltage signal from a filter. FIG. 8B is a graph showing a waveform of a voltage signal from a subtraction circuit. FIG. 9 is a circuit diagram showing a modified configuration of the winding switching device according to the third embodiment. FIG. 10 is a circuit diagram showing an example of the configuration of a winding switching device according to a fourth embodiment.

[0006] <Problem to be Solved by the Present Disclosure> The device disclosed in Patent Document 1 identifies a period during which the motor current is below a predetermined value using a processor such as a microcomputer, a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). However, the winding connection switching must be performed within a short period of time, on the order of several microseconds to sub-microseconds, which may be too short for program processing in a microcomputer. On the other hand, while FPGAs and ASICs are capable of high-speed processing, they have the problem of being expensive.

[0007] <Effects of the Present Disclosure> According to the present disclosure, it is possible to suppress the occurrence of surge voltage with an inexpensive configuration.

[0008] <Outline of Embodiments of the Present Disclosure> Below, an outline of embodiments of the present disclosure will be listed and described.

[0009] (1) A winding switching device according to this embodiment is a winding switching device for switching the connection states of multiple windings of a motor capable of switching the connection states of the multiple windings between a first connection state and a second connection state, and includes a detection unit that detects zero-crossing points in measurements of current sensors that measure currents flowing through the windings, and a switching unit that switches the connection states of the multiple windings between the first connection state and the second connection state when the detection unit detects the zero-crossing point. This eliminates the need for complex processing such as identifying periods during which the motor current is below a predetermined value. This allows the detection unit to be simplified, and surge voltages can be suppressed with an inexpensive configuration.

[0010] (2) In the above (1), the motor may be a multi-phase AC motor, the detection unit may detect the zero-crossing point for each phase, and the switching unit may switch the connection state of the plurality of windings between the first connection state and the second connection state for each phase. This allows the connection state of the windings to be switched at the zero-crossing point for each phase, thereby suppressing the occurrence of surge voltage in each phase.

[0011] (3) In the above (1) or (2), the detection unit may compare the output voltage from the current sensor with a reference voltage corresponding to the output voltage of the current sensor when the current flowing through the winding becomes zero, and detect the point in time when the output voltage from the current sensor matches the reference voltage as the zero-crossing point. This allows the detection unit to perform a simple process of comparing the output voltage from the current sensor with the reference voltage, simplifying the configuration of the detection unit.

[0012] (4) In the above (3), the detection unit may be a comparator. This allows the detection unit to be configured using an inexpensive comparator.

[0013] (5) In any one of (1) to (4) above, the detection unit may also share the current sensor with a power converter that converts DC power output from a battery into AC power and supplies the AC power to the motor. This reduces the number of current sensors in the entire system, resulting in a more inexpensive configuration.

[0014] (6) In the above (5), the current sensor may be disposed within the winding switching device, thereby enabling the winding switching device to measure the current flowing through the windings and detect the zero-crossing points by itself.

[0015] (7) In the above (6), the current sensor may be an AC current transformer. If the purpose is only to detect the zero-crossing points of the winding current, an AC current transformer (ACCT) that can measure only the AC component of the current can be used. Therefore, the occurrence of surge voltage can be suppressed with an inexpensive configuration.

[0016] (8) In the above (5), a signal line extending from the current sensor disposed in the power converter may be connected to the detection unit, thereby enabling the current sensor provided in the power converter to be used to detect zero-crossing points of the winding current.

[0017] (9) In the above (8), the winding switching device may further include a correction unit that removes a DC component from the output signal of the current sensor, and the detection unit may detect zero-crossing points of the output signal of the current sensor from which the DC component has been removed by the correction unit. This makes it possible to remove the DC component from the output signal of the current sensor and accurately detect zero-crossing points.

[0018] (10) A winding switching system according to this embodiment includes a motor capable of switching the connection state of multiple windings between a first connection state and a second connection state, a power converter that converts DC power output from a battery into AC power and supplies the AC power to the motor, and a winding switching device for switching the connection state of the multiple windings. The winding switching device includes a detector that detects zero-crossing points in a measurement value of a current sensor that measures current flowing through the windings, and a switching unit that switches the connection state of the multiple windings between the first connection state and the second connection state when the detector detects the zero-crossing point. This eliminates the need for complex processing such as identifying a period during which the motor current is below a predetermined value. This allows the detector to be configured simply, making it possible to suppress surge voltages at low cost.

[0019] The present disclosure can be realized not only as a winding switching device having the above-described characteristic configuration and a winding switching system including the winding switching device, but also as a winding switching method having steps corresponding to characteristic processes in the winding switching device, as a computer program for causing a computer to execute the characteristic processes, or as a semiconductor integrated circuit that realizes part or all of the winding switching device.

[0020] <Details of the embodiments of the present disclosure> Hereinafter, the details of the embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0021] [1. First Embodiment] [1-1. Winding Switching System] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to a first embodiment.

[0022] The winding switching system 10 is mounted on a vehicle (hereinafter referred to as an "electric vehicle") that is propelled by a motor, such as an electric vehicle, a plug-in hybrid vehicle, etc. The winding switching system 10 includes a motor 20, a power converter 30, a battery 40, a control device 50, and a winding switching device 100.

[0023] The motor 20 is a traction motor that generates propulsion power for the electric vehicle. The motor 20 is driven by three-phase AC power. An example of the motor 20 is a permanent magnet synchronous motor.

[0024] The battery 40 is a battery that supplies power to drive the motor 20. The battery 40 is a secondary battery, such as a lithium ion battery.

[0025] The power converter 30 is an inverter that converts DC power supplied from the battery 40 into three-phase AC power. The power converter 30 may have a function of converting three-phase AC power output when the motor 20 functions as a generator into DC power and charging the battery 40.

[0026] The power converter 30 includes U-phase, V-phase, and W-phase legs. The U-phase leg includes switches 31u and 32u, the V-phase leg includes switches 31v and 32v, and the W-phase leg includes switches 31w and 32w. The switches 31u, 32u, 31v, 32v, 31w, and 32w perform switching to convert DC power into three-phase AC power. The switches 31u, 32u, 31v, 32v, 31w, and 32w are, for example, insulated gate bipolar transistors (IGBTs) or power metal oxide semiconductor field-effect transistors (MOSFETs).

[0027] A power line 35u corresponding to the U phase extends from the U-phase leg, a power line 35v corresponding to the V phase extends from the V-phase leg, and a power line 35w corresponding to the W phase extends from the W-phase leg. In the power converter 30, a current sensor 33u is provided on the power line 35u, a current sensor 33v is provided on the power line 35v, and a current sensor 33w is provided on the power line 35w. The current sensor 33u detects the current value of the U-phase current Iu. The current sensor 33v detects the current value of the V-phase current Iv. The current sensor 33w detects the current value of the W-phase current Iw. The current sensors 33u, 33v, and 33w can detect the current values ​​of the currents Iu, Iv, and Iw flowing through the power lines 35u, 35v, and 35w, including DC and AC components. The current sensors 33u, 33v, and 33w are, for example, DCCTs (direct current transformers) or shunt resistors.

[0028] The winding switching device 100 is disposed between the motor 20 and the power converter 30. However, the position of the winding switching device 100 is not limited to between the motor 20 and the power converter 30. The power converter 30 and the winding switching device 100 are connected by power lines 35u, 35v, and 35w, and the winding switching device 100 and the motor 20 are connected by a plurality of power lines 25. The winding switching device 100 switches the connection state of a plurality of windings of the motor 20. The configuration of the winding switching device 100 will be described later. Three-phase AC currents Iu, Iv, and Iw output from the power converter 30 are supplied to the motor 20 via the winding switching device 100.

[0029] The control device 50 controls the power converter 30 and the winding switching device 100. Specifically, signal lines extend from the control device 50 to each of the switches 31u, 32u, 31v, 32v, 31w, and 32w, and the control device 50 controls the on / off timing of the switches 31u, 32u, 31v, 32v, 31w, and 32w. A signal line extends from the control device 50 to the winding switching device 100, and the control device 50 outputs a switching command signal to the winding switching device 100 to command the switching of the connection state of the windings.

[0030] The control device 50 includes a processor, a memory, an input / output interface, a communication interface, etc. (not shown). The processor is, for example, a CPU (Central Processing Unit). However, the processor is not limited to a CPU. The processor may also be a GPU (Graphics Processing Unit). The processor may also be, for example, an ASIC (Application Specific Integrated Circuit) or a programmable logic device such as a gate array or FPGA (Field Programmable Gate Array).

[0031] [1-2. Configuration of the Winding Switching Device] Figure 2 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. The motor 20 includes a plurality of windings 21u, 22u, 21v, 22v, 21w, and 22w. The windings 21u and 22u correspond to the U phase, the windings 21v and 22v correspond to the V phase, and the windings 21w and 22w correspond to the W phase. However, the number of windings for each phase is not limited to two and may be three or more. The windings 22u, 22v, and 22w are connected at a neutral point 23.

[0032] The winding switching device 100 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w for each phase between a series connection state and a parallel connection state. The winding switching device 100 includes current sensors 101u, 101v, and 101w, zero-cross detection circuits 102u, 102v, and 102w, control circuits 103u, 103v, and 103w, and switching circuits 104u, 104v, and 104w.

[0033] The zero-crossing detection circuits 102u, 102v, and 102w detect zero-crossing points of the measured values ​​of the current sensors 101u, 101v, and 101w. In a more specific example, the zero-crossing detection circuits 102u, 102v, and 102w compare the output voltages from the current sensors 101u, 101v, and 101w with zero voltage and detect the zero-crossing points as the points at which the output voltages from the current sensors 101u, 101v, and 101w match zero voltage. The zero voltage is an example of a reference voltage. The reference voltage is a voltage corresponding to the output voltages of the current sensors 101u, 101v, and 101w when the currents flowing through the windings 21u, 22u, 21v, 22v, 21w, and 22w become zero current, and is not limited to zero voltage. The zero-crossing detection circuits 102u, 102v, and 102w are an example of a detection unit.

[0034] The switching circuits 104u, 104v, and 104w switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series connection state and a parallel connection state when the zero-crossing detection circuits 102u, 102v, and 102w detect a zero-crossing point. The switching circuits 104u, 104v, and 104w are an example of a switching unit. The series connection state is an example of a first connection state, and the parallel connection state is an example of a second connection state.

[0035] The following describes the connection relationship between the winding switching device 100, the power line 35u, and the motor 20 for the U phase. The same applies to the V and W phases, so a description thereof will be omitted.

[0036] The power line 35u is connected to one end of the winding 21u. A power line 212u extends from the other end of the winding 21u. A power line 221u extends from one end of the winding 22u, and a power line 222u extends from the other end.

[0037] The switching circuit 104u includes semiconductor relays 111u, 112u, and 113u. The semiconductor relays 111u, 112u, and 113u are, for example, IGBTs or power MOSFETs.

[0038] The power line 35u is drawn into the winding switching device 100. Inside the winding switching device 100, the power line 35u branches off at a midpoint and is connected to a first terminal of a semiconductor relay 111u. A second terminal of the semiconductor relay 111u is connected to a first terminal of a semiconductor relay 112u. A power line 221u extending from the winding 22u is connected to the connection point between the second terminal of the semiconductor relay 111u and the first terminal of the semiconductor relay 112u.

[0039] A second terminal of the semiconductor relay 112u is connected to a first terminal of the semiconductor relay 113u. A power line 212u extending from the winding 21u is connected to the connection point between the second terminal of the semiconductor relay 112u and the first terminal of the semiconductor relay 113u. A power line 222u extending from the winding 22u is connected to a second terminal of the semiconductor relay 113u.

[0040] When the semiconductor relays 111u and 113u are in the OFF state and the semiconductor relay 112u is in the ON state, the windings 21u and 22u are connected in series. When the semiconductor relays 111u and 113u are in the ON state and the semiconductor relay 112u is in the OFF state, the windings 21u and 22u are connected in parallel.

[0041] Signal lines extending from the control circuit 103u are connected to the gate terminals of the semiconductor relays 111u, 112u, and 113u, respectively.

[0042] The power lines 212u, 221u, and 222u extend from the motor 20 and are drawn into the winding switching device 100. A current sensor 101u is attached to the power line 221u. However, the current sensor 101u may be attached to the power lines 35u, 212u, or 222u instead of the power line 221u. The current sensor 101u detects a U-phase current flowing through the power line 221u. The current sensor 101u is, for example, an ACCT that detects only the AC component of the current.

[0043] A signal line extending from the current sensor 101u is connected to the zero-cross detection circuit 102u. A signal line transmitting an output signal of the zero-cross detection circuit 102u (hereinafter referred to as the "zero-cross detection signal") extends from the zero-cross detection circuit 102u to the control circuit 103u. Furthermore, a signal line extending from the control device 50 is connected to the control circuit 103u.

[0044] The zero-crossing detection circuit 102u detects zero-crossing points of the winding current flowing through the power line 221u measured by the current sensor 101u. The zero-crossing detection circuit 102u is a comparator. For example, the inverting input of the comparator is set to a zero reference voltage, and the output signal of the current sensor 101u is applied to the non-inverting input. As a result, the output of the comparator changes from low to high when the AC signal output from the current sensor 101u crosses the zero reference voltage (zero-crossing point).

[0045] 3 is a circuit diagram showing an example of the configuration of the control circuit 103u. The control circuit 103u includes AND circuits 131 and 133, a NOT circuit 132, and a latch circuit 120. A signal line extending from the zero-crossing detection circuit 102u is connected to a first input terminal of the AND circuit 131 and a first input terminal of the AND circuit 133. A signal line extending from the control device 50 is connected to a second input terminal of the AND circuit 131. Furthermore, a signal line from the control device 50 is connected to an input terminal of the NOT circuit 132. A signal line extending from the output terminal of the NOT circuit 132 is connected to a second input terminal of the AND circuit 133.

[0046] The latch circuit 120 is an RS flip-flop. The output terminal of the AND circuit 131 is connected to the input S (set) of the RS flip-flop 120. The output terminal of the AND circuit 133 is connected to the input R (reset) of the RS flip-flop 120. The RS flip-flop 120 includes two NOT circuits 121 and 123 and two NAND circuits 122 and 124. However, the RS flip-flop 120 may also be configured using two NOR circuits.

[0047] The output Q of the RS flip-flop 120 is connected to the gates of the semiconductor relays 111u and 113u, and the output Q bar of the RS flip-flop 120 is connected to the gate of the semiconductor relay 112u.

[0048] The latch circuit 120 may be configured with a D flip-flop instead of the RS flip-flop.

[0049] [1-3. Operation of the Winding Switching Device] Next, the operation of the winding switching device 100 will be described. Note that the following description will be focused on the operation of switching the connection states of the windings 21u, 22u for the U phase. The same applies to the V and W phases, so their description will be omitted.

[0050] FIG. 4 is a timing chart showing an example of transition of the states of the signals of the winding switching device 100 according to the first embodiment.

[0051] The current sensor 101u measures the winding current Iu flowing through the power line 221u. The zero-crossing detection circuit 102u detects zero-crossing points in the measured value of the winding current Iu. That is, the zero-crossing detection signal output from the zero-crossing detection circuit 102u is low when the winding current Iu is not zero and goes high when the winding current Iu becomes zero. In FIG. 4 , the zero-crossing detection signal is low under normal conditions and high at times T1, T2, T3, and T4.

[0052] The control device 50 sets the value of the switching command signal to Low when windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 are connected in series, and sets the value of the switching command signal to High when windings 21u, 22u, 21v, 22v, 21w, and 22w are connected in parallel. In Fig. 4, the switching command signal is Low in the initial state and changes to High at a point in time between times T1 and T2. The switching command signal changes to Low again at a point in time between times T3 and T4.

[0053] The zero-crossing detection signal and the switching command signal are input to an AND circuit 131. The AND circuit 131 outputs a low signal when the zero-crossing detection signal and the switching command signal are a combination of (low, low), (low, high), and (high, low). The AND circuit 131 outputs a high signal when the zero-crossing detection signal and the switching command signal are a combination of (high, high). That is, a low signal is normally input to S of the RS flip-flop 120, and a high signal is input when a zero-crossing point of the winding current Iu is detected and a parallel connection command for the windings 21u, 22u, 21v, 22v, 21w, and 22w is given. In FIG. 4 , the input signal to S is high at times T2 and T3.

[0054] The zero-crossing detection signal and an inverted signal of the switching command signal (the output signal of the NOT circuit 132) are input to the AND circuit 133. The AND circuit 133 outputs a low signal when the zero-crossing detection signal and the switching command signal are combined as (low, low), (high, low), or (high, high). The AND circuit 133 outputs a high signal when the zero-crossing detection signal and the switching command signal are combined as (high, low). That is, a low signal is input to R of the RS flip-flop 120 under normal circumstances, and a high signal is input when a zero-crossing point of the winding current Iu is detected and a command to connect the windings 21u, 22u, 21v, 22v, 21w, and 22w in series is given. In FIG. 4 , the input signal to R is high at times T1 and T4.

[0055] The RS flip-flop 120 holds the previous output values ​​of Q and Q bar when the inputs S and R are Low and Low. The RS flip-flop 120 outputs Low and High for Q and Q bar when the inputs S and R are Low and High, and outputs High and Low for Q and Q bar when the inputs S and R are High and Low. The RS flip-flop 120 prohibits the combination of High and High for the inputs S and R.

[0056] 4, Q is low and Q is high until time T2. Therefore, until time T2, the semiconductor relays 111u and 113u are in the off state and the semiconductor relay 112u is in the on state. Therefore, the windings 21u and 22u are connected in series.

[0057] At time T2, Q changes from low to high and Q changes from high to low. Therefore, the semiconductor relays 111u and 113u change from off to on, and the semiconductor relay 112u changes from on to off. As a result, the connection state of the windings 21u and 22u changes from a series connection state to a parallel connection state.

[0058] From time T2 to T4, Q is high and Q is low. Therefore, from time T2 to T4, the semiconductor relays 111u and 113u are maintained in the on state, and the semiconductor relay 112u is maintained in the off state. As a result, the windings 21u and 22u are maintained in a parallel connection state.

[0059] At time T4, Q changes from high to low, and Q changes from low to high. Therefore, the semiconductor relays 111u and 113u change from on to off, and the semiconductor relay 112u changes from off to on. As a result, the connection state of the windings 21u and 22u switches from a parallel connection state to a series connection state.

[0060] After time T4, Q is low and Q is high. Therefore, until time T2, the semiconductor relays 111u and 113u remain off and the semiconductor relay 112u remains on. As a result, the windings 21u and 22u are maintained in a series connection state.

[0061] As described above, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w can be switched between a series connection state and a parallel connection state at the timing of the zero-crossing points of the winding currents Iu, Iv, and Iw. Therefore, the occurrence of surge voltages is suppressed. Furthermore, complex processing such as identifying the period during which the winding currents Iu, Iv, and Iw are equal to or less than a predetermined value is not required, and the winding switching device 100 can be configured without using a processor such as a CPU, FPGA, or ASIC.

[0062] [2. Second Embodiment] A winding switching device according to a second embodiment switches the connection state of a plurality of windings of a motor between a full connection state in which all of the plurality of windings are connected, and a partial connection state in which some of the plurality of windings are connected.

[0063] 5 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. The motor 20A includes a plurality of windings 24u, 25u, 24v, 25v, 24w, and 25w. The windings 24u and 25u correspond to the U phase, the windings 24v and 25v correspond to the V phase, and the windings 24w and 25w correspond to the W phase. However, the number of windings for each phase is not limited to two and may be three or more.

[0064] The winding switching device 100A switches the connection states of the windings 24u, 25u, 24v, 25v, 24w, and 25w for each phase between a fully connected state and a partially connected state. The winding switching device 100A includes current sensors 131u, 131v, and 131w, zero-crossing detection circuits 102u, 102v, and 102w, control circuits 103u, 103v, and 103w, and switching circuits 140u, 140v, and 140w.

[0065] The zero-cross detection circuits 102u, 102v, and 102w detect zero-cross points of the measured values ​​of the current sensors 131u, 131v, and 131w. The configurations of the zero-cross detection circuits 102u, 102v, and 102w are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0066] The switching circuits 140u, 140v, and 140w switch the connection states of the windings 24u, 25u, 24v, 25v, 24w, and 25w between a fully connected state and a partially connected state when the zero-crossing detection circuits 102u, 102v, and 102w detect a zero-crossing point. The switching circuits 140u, 140v, and 140w are an example of a switching unit. The fully connected state is an example of a first connected state, and the partially connected state is an example of a second connected state.

[0067] The power line 35u is connected to one end of the winding 24u. The other end of the winding 24u and one end of the winding 25u are connected to each other, and a power line 241u extends from the midpoint between the windings 24u and 25u. The power line 241u branches into power lines 242u and 243w. A power line 251u extends from the other end of the winding 25u. The power line 251u branches into power lines 252u and 253w.

[0068] Power line 35v is connected to one end of winding 24v. The other end of winding 24v and one end of winding 25v are connected to each other, and power line 241v extends from the midpoint between windings 24v and 25v. Power line 241v branches into power lines 242v and 243u. Power line 251v extends from the other end of winding 25v. Power line 251v branches into power lines 252v and 253u.

[0069] Power line 35w is connected to one end of winding 24w. The other end of winding 24w and one end of winding 25w are connected to each other, and power line 241w extends from the midpoint between windings 24w and 25w. Power line 241w branches into power lines 242w and 243v. Power line 251w extends from the other end of winding 25w. Power line 251w branches into power lines 252w and 253v.

[0070] The switching circuit 140u includes semiconductor relays 141u and 142u. The switching circuit 140v includes semiconductor relays 141v and 142v. The switching circuit 140w includes semiconductor relays 141w and 142w. The semiconductor relays 141u, 142u, 141v, 142v, 141w, and 142w are, for example, IGBTs or power MOSFETs.

[0071] In the switching circuit 140u, a first terminal of a semiconductor relay 141u is connected to a power line 242u, and a second terminal of the semiconductor relay 142u is connected to a power line 252u, and a second terminal of the semiconductor relay 142u is connected to a power line 253u. The connection relationship between the switching circuits 140v and 140w is the same as that of the switching circuit 140u, and therefore will not be described here.

[0072] When the semiconductor relays 141u, 141v, and 141w are in the OFF state and the semiconductor relays 142u, 142v, and 142w are in the ON state, all of the windings 24u, 25u, 24v, 25v, 24w, and 25w are connected, resulting in a fully connected state. When the semiconductor relays 141u, 141v, and 141w are in the ON state and the semiconductor relays 142u, 142v, and 142w are in the OFF state, only the windings 24u, 24v, and 24w are connected, resulting in a partially connected state.

[0073] The power line 35u is drawn into the winding switching device 100. A current sensor 131u is attached to the power line 35u. The current sensor 131u detects the U-phase current flowing through the power line 35u. The current sensor 131u is, for example, an ACCT that detects only the AC component of the current. A signal line extending from the current sensor 131u is connected to the zero-crossing detection circuit 102u. The same applies to the V-phase and W-phase.

[0074] The output Q of the RS flip-flop 120 of the control circuit 103u is connected to the gate of the semiconductor relay 141u. The output Q bar of the RS flip-flop 120 is connected to the gate of the semiconductor relay 142u. The same applies to the V-phase and W-phase.

[0075] The other configurations of the winding switching device 100A according to the second embodiment are similar to those of the winding switching device 100 according to the first embodiment, so the same components are given the same reference numerals and their description will be omitted.

[0076] In the second embodiment, the control device 50 sets the value of the switching command signal to Low when the windings 24u, 25u, 24v, 25v, 24w, and 25w of the motor 20 are to be fully connected, and sets the value of the switching command signal to High when the windings 24u, 25u, 24v, 25v, 24w, and 25w are to be partially connected.

[0077] When the windings are in the fully connected state, output Q goes low and output Q goes high at the timing when both the zero-crossing detection signal and the switching command signal go high. Therefore, semiconductor relay 141u changes from the on state to the off state, and semiconductor relay 142u changes from the off state to the on state. The same applies to the V-phase and W-phase. Therefore, the connection states of windings 24u, 25u, 24v, 25v, 24w, and 25w change from the fully connected state to the partially connected state.

[0078] When the windings are in the partially connected state, the zero-crossing detection signal goes high and the switching command signal goes low, causing output Q to go high and output Q bar to go low. Therefore, semiconductor relay 141u changes from the off state to the on state, and semiconductor relay 142u changes from the on state to the off state. The same applies to the V-phase and W-phase. Therefore, the connection states of windings 24u, 25u, 24v, 25v, 24w, and 25w are switched from the partially connected state to the fully connected state.

[0079] As described above, the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w can be switched between a fully connected state and a partially connected state at the timing of the zero crossing points of the winding currents Iu, Iv, and Iw.

[0080] 6 is a circuit diagram showing an example of the configuration of a winding switching device according to a third embodiment. In a winding switching device 100B according to the third embodiment, signal lines 331u, 331v, and 331w extending from current sensors 33u, 33v, and 33w arranged in a power converter 30 are connected to zero-crossing detection circuits 102u, 102v, and 102w.

[0081] In a more specific example, the winding switching device 100B includes correction circuits 150u, 150v, and 150w that remove DC components from the output signals of the current sensors 33u, 33v, and 33w. The correction circuits 150u, 150v, and 150w are examples of correction units.

[0082] The following description will be given of the configuration of the correction circuit 150u for the U phase, as a representative example. The V and W phases are similar, so their descriptions will be omitted.

[0083] The signal line 331u extending from the power converter 30 is drawn into the winding switching device 100B. That is, the signal line 331u extending from the current sensor 33u is drawn directly into the winding switching device 100B without passing through a signal processing circuit or the like. Within the winding switching device 100B, the signal line 331u branches, and one signal line is connected to a first input terminal of the subtraction circuit 152u. The other signal line is connected to an input terminal of the filter 151u. A signal line extends from the output terminal of the filter 151u and is connected to a second input terminal of the subtraction circuit 152u. A signal line extends from the output terminal of the subtraction circuit 152u and is connected to the zero-crossing detection circuit 102u.

[0084] 7 is a circuit diagram showing an example of the configuration of the correction circuit. The filter 151u is a low-pass filter including a resistor and a capacitor. The filter 151u removes frequency components equal to or higher than a threshold, which is lower than the frequency of the winding currents Iu, Iv, and Iw at the time when the connection state of the windings of the motor 20 is switched, from the voltage signal Vin output from the current sensor 33u. The filter 151u outputs a voltage Vfilt obtained by removing the above frequency components from the input voltage Vin.

[0085] The subtraction circuit 152u receives the voltage signal Vin from the current sensor 33u and the voltage signal Vfilt from the filter 151u, and outputs a differential voltage Vout between Vin and Vfilt.

[0086] 8A is a graph showing the waveforms of the voltage signal Vin from the current sensor 33u and the voltage signal Vfilt from the filter 151u. In FIG. 8A, the vertical axis represents voltage, and the horizontal axis represents time. The voltage signal Vin output from the current sensor 33u includes an AC component corresponding to the U phase and a DC component. Therefore, the voltage signal Vin exhibits a waveform in which an AC current having the same frequency as the AC current corresponding to the U phase is offset by the DC component. In the example of FIG. 8A, the AC waveform is offset by a DC component of 0.2 V.

[0087] The filter 151u removes AC components from the voltage signal Vin. Therefore, the voltage signal output from the filter 151u has the DC component. That is, in the example of FIG. 8A, Vfilt is a DC voltage of 0.2 V.

[0088] 8B is a graph showing the waveform of the voltage signal from the subtraction circuit 152u. The subtraction circuit 152u subtracts Vfilt from the voltage signal Vin output from the current sensor 33u. Therefore, the voltage signal Vout output from the subtraction circuit 152u is a signal obtained by correcting the offset amount of Vin to zero, i.e., an AC voltage signal that does not contain a DC component.

[0089] With the above configuration, the zero-crossing detection circuit 102u can detect the zero-crossing point in the U-phase winding current Iu without being affected by the DC component contained in the output voltage of the current sensor 33u.

[0090] The configuration of the correction circuit 150u is not limited to the above. Fig. 9 is a circuit diagram showing a modified configuration of the winding switching device according to the third embodiment. In the modified configuration shown in Fig. 9, the correction circuit is made up of filters 153u, 153v, and 153w. The filters 153u, 153v, and 153w are high-pass filters that pass only frequency components equal to or greater than a threshold that is lower than the frequency of the winding currents Iu, Iv, and Iw at the time of switching the winding connection state of the motor 20. Even with this configuration, DC components can be removed from the output signals of the current sensors 33u, 33v, and 33w.

[0091] 10 is a circuit diagram showing an example of the configuration of a winding switching device according to a fourth embodiment. A winding switching device 100C according to the fourth embodiment includes current sensors 101U, 101V, and 101W.

[0092] The current sensor 101U is attached, for example, to the power line 35u drawn into the winding switching device 100C. However, the current sensor 101U may be attached to the power line 211u, 212u, or 222u instead of the power line 35u. The current sensor 101U detects the U-phase current flowing through the power line 35u. Similarly, the current sensors 101V and 101W are attached to the power lines 35v and 35w. The current sensors 101U, 101V, and 101W can detect the current values ​​of the currents flowing through the power lines 35u, 35v, and 35w, including DC and AC components. The current sensor 101U is, for example, a DCCT (direct current transformer) or a shunt resistor.

[0093] Signal lines 331U, 331V, and 331W extending from the current sensors 101U, 101V, and 101W are connected to the zero-cross detection circuits 102u, 102v, and 102w.

[0094] In a more specific example, the winding switching device 100C includes correction circuits 150u, 150v, and 150w that remove DC components from the output signals of the current sensors 101U, 101V, and 101W. The correction circuits 150u, 150v, and 150w are the same as the correction circuits 150u, 150v, and 150w described in the second embodiment.

[0095] Each of the signal lines 331U, 331V, and 331W branches off midway, and the branched ends are connected to the control device 50. Output signals from the current sensors 101U, 101V, and 101W are input to the control device 50. In this embodiment, the current sensors 33u, 33v, and 33w provided in the power converter 30 are omitted.

[0096] The control device 50 performs feedback control of the motor 20 based on the current values ​​detected by the current sensors 101U, 101V, and 101W. That is, the control device 50 determines the voltage values ​​to be applied to the windings 21u, 22u, 21v, 22v, 21w, and 22w based on the current values ​​of the U-phase, V-phase, and W-phase currents input to the motor 20, and turns on and off the switches 31u, 32u, 31v, 32v, 31w, and 32w by PWM control in accordance with the determined voltage values. That is, in this embodiment, the current sensors 101U, 101V, and 101W are also used to control the power converter 30. This allows the number of current sensors in the entire winding switching system to be reduced.

[0097] [4. Supplementary Note] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope thereof.

[0098] 10 Winding switching system 20 Motor 21u, 22u, 21v, 22v, 21w, 22w Winding 23 Neutral point 25 Power line 30 Power converter 31u, 32u, 31v, 32v, 31w, 32w Switch 33u, 33v, 33w Current sensor 35u, 35v, 35w Power line 40 Battery 50 Control device 100 Winding switching device 101u, 101v, 101w Current sensor 102u, 102v, 102w Zero cross detection circuit (detection unit) 103u, 103v, 103w Control circuit 104u, 104v, 104w Switching circuit (switching unit) 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w Semiconductor relays 212u, 221u, 222u, 212v, 221v, 222v, 212w, 221w, 222w Power lines 131, 133 AND circuit 132 NOT circuit 120 Latch circuit (RS flip-flop) 121, 123 NOT circuit 122, 124 NAND circuit 20A Motor 24u, 25u, 24v, 25v, 24w, 25w Winding 100A Winding switching device 131u, 131v, 131w Current sensor 140u, 140v, 140w Switching circuit 141u, 142u, 141v, 142v, 141w, 142w Semiconductor relays 241u, 242u, 243u, 251u, 252u, 253u, 241v, 242v, 243v, 251v, 252v, 253v, 241w, 242w, 243w, 251w, 252w, 253w Power line 100B Winding switching device 150u, 150v, 150w Correction circuit 151u, 151v, 151w Filter 152u, 152v, 152w Subtraction circuit 153u, 153v, 153w Filter 331u, 331v, 331w Signal line 100C Winding switching device 101U, 101V, 101W Current sensor 331U, 331V, 331W Signal line T1, T2, T3, T4 Time

Claims

1. A winding switching device for switching a connection state of a plurality of windings of a motor capable of switching a connection state of the plurality of windings between a first connection state and a second connection state, comprising: a detection unit that detects a zero-cross point of a measurement value of a current sensor that measures a current flowing through the winding and outputs a zero-cross detection signal; a switching unit that switches a connection state of the plurality of windings between the first connection state and the second connection state; a latch circuit that receives input of a switching command signal that commands switching of a connection state of the winding between the first connection state and the second connection state and the zero-cross detection signal output from the detection unit, and starts outputting a control signal to the switching unit at a timing when the switching command signal and the zero-cross detection signal are both input, for switching the plurality of windings in the first connection state to the second connection state, and stops outputting the control signal at a timing when the switching command signal is not input and the zero-cross detection signal is input; Equipped with Winding switching device.

2. the motor is a polyphase AC motor; The detection unit detects the zero crossing point for each phase, the switching unit switches a connection state of the plurality of windings between the first connection state and the second connection state for each phase. The winding switching device according to claim 1 .

3. the detection unit compares the output voltage from the current sensor with a reference voltage corresponding to the output voltage of the current sensor when the current flowing through the winding becomes zero, and detects a time point when the output voltage from the current sensor coincides with the reference voltage as a zero crossing point. The winding switching device according to claim 1 .

4. The detection unit is a comparator. The winding switching device according to claim 3.

5. the detection unit converts DC power output from a battery into AC power and controls a power converter that supplies the AC power to the motor, and the current sensor is also used for controlling the power converter. The winding switching device according to any one of claims 1 to 4.

6. The current sensor is disposed within the winding switching device. The winding switching device according to claim 5.

7. The current sensor is an AC current transformer. The winding switching device according to claim 6.

8. the current sensor is disposed within the power converter; A signal line extending from the current sensor is connected to the detection unit. The winding switching device according to claim 5.

9. The winding switching device further includes a correction unit that removes a DC component from the output signal of the current sensor, The detection unit detects a zero-crossing point of the output signal of the current sensor from which the DC component has been removed by the correction unit. The winding switching device according to claim 8.

10. a motor capable of switching a connection state of a plurality of windings between a first connection state and a second connection state; a power converter that converts DC power output from a battery into AC power and supplies the AC power to the motor; A winding switching device for switching a connection state of the plurality of windings; Equipped with The winding switching device includes: a detection unit that detects a zero-cross point of a measurement value of a current sensor that measures a current flowing through the winding and outputs a zero-cross detection signal; a switching unit that switches a connection state of the plurality of windings between the first connection state and the second connection state; a latch circuit that receives input of a switching command signal that commands switching of a connection state of the winding between the first connection state and the second connection state and the zero-cross detection signal output from the detection unit, and starts outputting a control signal to the switching unit at a timing when the switching command signal and the zero-cross detection signal are both input, for switching the plurality of windings in the first connection state to the second connection state, and stops outputting the control signal at a timing when the switching command signal is not input and the zero-cross detection signal is input; Including, Winding switching system.