Motor control device and motor control method

Abstract

A motor control device has: a three-phase motor winding; and a thermistor that measures the temperature of any one or two of the coils, the motor control device having a coil temperature estimation section that respectively calculates estimated temperatures of the three-phase coils based on current values flowing through the three-phase motor winding, in a case where a difference between the estimated temperatures of the three-phase motor winding is greater than a prescribed value, controlling the motor based on the estimated temperatures of the three-phase motor winding, and in a case where the difference between the estimated temperatures of the three-phase motor winding is below the prescribed value, controlling the motor based on a measured value of the thermistor.

Description

Technical Field

[0001] This invention relates to a motor control device and a motor control method. Background Technology

[0002] As background technology for this application, regarding temperature estimation of a motor in motor control, the following patent document 1 is known. In patent document 1, an estimation error corrector is disclosed that has an estimation error correction device that estimates the temperature distribution or local maximum temperature of multiple regions in the excitation coil, and can perform a temperature estimation that takes into account the temperature distribution of the excitation coil with high accuracy.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-058131 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the configuration of Patent Document 1, for example, when sensors cannot be installed on all three phases due to the layout of the motor, when the motor rotates at 0 rpm (r / min), the heat generated by the U phase, V phase, and W phase is different due to the deviation of the three-phase current, resulting in a temperature difference. Therefore, it is difficult to protect the motor using only the existing thermistor-based protection method.

[0008] Therefore, the purpose of this invention is to provide a motor control device that can perform three-phase overheat protection even without installing sensors on all three phases (U, V, and W) of the motor.

[0009] Technical means to solve the problem

[0010] The present invention discloses a motor control device for controlling a motor comprising: a three-phase motor winding consisting of a U-phase coil, a V-phase coil, and a W-phase coil; and a thermistor for measuring the temperature of any one or two coils of the three-phase motor winding. The motor control device includes a coil temperature estimation unit that calculates the estimated temperatures of the U-phase coil, the V-phase coil, and the W-phase coil based on the current flowing through the three-phase motor winding. If the difference between the estimated temperatures of the three-phase motor winding is greater than a predetermined value, the motor control device controls the motor based on the estimated temperatures of the three-phase motor winding. If the difference between the estimated temperatures of the three-phase motor winding is less than the predetermined value, the motor control device controls the motor based on the measured values ​​of the thermistor.

[0011] The effects of the invention

[0012] According to the present invention, a motor control device is provided that can perform three-phase overheat protection even if sensors are not installed on all three phases (U, V, and W) of the motor. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a hybrid electric vehicle equipped with the motor of this embodiment.

[0014] Figure 2 This is the circuit diagram of inverter device 600.

[0015] Figure 3 This is a cross-sectional view of the motor according to this embodiment.

[0016] Figure 4 This is a schematic diagram of the thermal loop used for temperature estimation calculations.

[0017] Figure 5 This is a flowchart for the case where protection is based solely on thermistors.

[0018] Figure 6 It is a flowchart that combines thermistor-based protection and temperature estimation calculations, and uses the temperature difference of the three-phase estimated values ​​in the switching determination.

[0019] Figure 7 It is a flowchart that combines thermistor-based protection and temperature estimation calculations, and uses the temperature difference between the rotational speed and the estimated three-phase values ​​in the switching determination.

[0020] Figure 8 This is a schematic diagram of the operation under the condition of protection based solely on thermistors.

[0021] Figure 9 This is a schematic diagram of the operation when combining thermistor-based protection and temperature estimation-based protection.

[0022] Figure 10 It refers to the torque-speed characteristics of the motor. Detailed Implementation

[0023] (First embodiment and configuration of the motor control device)

[0024] The following describes how the present invention is carried out with reference to the accompanying drawings. Figure 1 This is a diagram showing a schematic structure of a hybrid electric vehicle equipped with a motor according to an embodiment of the present invention.

[0025] The vehicle 100 is equipped with an engine 120, a first motor 200, a second motor 202, and a battery 180. The transfer of DC power between the battery 180 and the motors 200 and 202 is performed via an inverter device 600. When the motors 200 and 202 require driving force, the battery 180 supplies DC power to them. During regenerative braking, the battery 180, in turn, draws DC power from the motors 200 and 202.

[0026] Although not shown, the vehicle 100 is also equipped with a battery for supplying low-voltage power (e.g., 14-volt power) to supply DC power to the control circuit described below.

[0027] The rotational torque generated by the engine 120 and motors 200 and 202 is transmitted to the front tires 110 via the transmission 130 and differential gear 160. The transmission 130 is controlled by the transmission control unit 134. The engine 120 is controlled by the engine control unit 124. The battery 180 is controlled by the battery control unit 184. The transmission control unit 134, the engine control unit 124, the battery control unit 184, the inverter unit 600, and the integrated control unit 170 are connected via communication line 174.

[0028] The high-voltage battery 180 is composed of secondary batteries such as lithium-ion batteries or nickel-metal hydride batteries, and outputs high-voltage DC power of 250 volts to 600 volts or more. The battery control device 184 outputs the charging and discharging status of the battery 180 and the status of each unit cell constituting the battery 180 to the integrated control device 170 via the communication line 174.

[0029] The integrated control unit 170 is a higher-level control unit than the transmission control unit 134, engine control unit 124, inverter unit 600, and battery control unit 184. The integrated control unit 170 receives information indicating the states of the transmission control unit 134, engine control unit 124, inverter unit 600, and battery control unit 184 via communication line 174. Based on this information, the integrated control unit 170 calculates control commands. The calculated control commands are then transmitted to the respective units 134, 124, 600, and 184 via communication line 174.

[0030] The control command calculation of the integrated control unit 170 is explained. When it is determined, based on information from the battery control unit 184, that the battery 180 needs charging, the integrated control unit 170 issues a power generation operation instruction to the inverter unit 600. Thus, during regenerative driving, the battery 180 can obtain DC power from the inverter unit 600. Furthermore, the integrated control unit 170 primarily manages the output torque of the engine 120 and motors 200 and 202, and performs calculations on the combined torque and torque distribution ratio of the output torque of the engine 120 and motors 200 and 202. Control commands based on the results of these calculations are sent to the transmission control unit 134, the engine control unit 124, and the inverter unit 600.

[0031] The inverter device 600 is equipped with power semiconductors that constitute an inverter for operating motors 200 and 202. Based on torque commands received from the integrated control unit 170, the inverter device 600 controls the switching operation of the power semiconductors via its internal control unit to generate torque output or power generation according to the commands. Through the switching operation of these power semiconductors, motors 200 and 202 are controlled to operate as electric motors or generators.

[0032] When motors 200 and 202 are operating as electric motors, DC power from the high-voltage battery 180 is supplied to the DC terminals of the inverter in the inverter device 600. The inverter device 600 converts the supplied DC power into three-phase AC power by controlling the switching operation of the power semiconductor, and supplies it to motors 200 and 202. Thus, motors 200 and 202 function as electric motors.

[0033] On the other hand, when motors 200 and 202 operate as generators, the rotors of motors 200 and 202 are driven to rotate by the rotational torque applied from the front wheel tires 110 during regenerative driving. This generates three-phase alternating current (AC) power in the stator windings of motors 200 and 202. The generated AC power is converted into DC power by inverter device 600, and this DC power is supplied to a high-voltage battery 180, thereby charging the battery 180.

[0034] Figure 2 yes Figure 1 Circuit diagram of inverter device 600.

[0035] The inverter device 600 is electrically connected to a power module 610 for operating the motor 200 and a power module 620 for operating the motor 202.

[0036] Power modules 610 and 620 convert the DC power supplied from battery 180 into three-phase AC power, which is then supplied to the armature windings, i.e., stator windings, of the corresponding motors 200 and 202. Additionally, during regenerative braking, power modules 610 and 620 convert the AC power induced in the stator windings of motors 200 and 202 into DC power, which is then supplied to battery 180.

[0037] The first inverter device includes: a power module 610; a first drive circuit 652 that controls the switching operation of each power semiconductor 21 of the power module 610; and a current sensor 660 that detects the current of the motor 200. The drive circuit 652 is disposed on a drive circuit board 650 related to the drive of the switching operation of the power module 610. The current sensor 660, which detects the three-phase AC power output from the power module 610 to the motor 200, can be disposed on each of the three phases, or, as far as possible, disposed on only one phase.

[0038] On the other hand, the second inverter device includes: a power module 620; a second drive circuit 656 that controls the switching operation of each power semiconductor 21 in the power module 620; and a current sensor 662 that detects the current of the motor 202. The drive circuit 656 is disposed on a drive circuit board 654 related to the drive of the switching operation of the power module 620. The current sensor 662, which detects the three-phase AC power output from the power module 620 to the motor 202, can be disposed on each of the three phases, or, as far as possible, disposed on only one phase.

[0039] Power modules 610 and 620 have a three-phase bridge circuit, with corresponding series circuits connected in parallel between the positive and negative terminals of battery 180. Each series circuit has a power semiconductor 21 forming the upper arm and a power semiconductor 22 forming the lower arm.

[0040] In this embodiment, IGBTs (Insulated Gate Bipolar Transistors) are used as switching power semiconductor devices in power semiconductors 21 and 22. An IGBT has three electrodes: a collector, an emitter, and a gate. A diode 38 is electrically connected between the collector and emitter of the IGBT. The diode 38 has two electrodes: a cathode and an anode. With the direction from the emitter to the collector of the IGBT being the positive direction, the cathode is electrically connected to the collector, and the anode is electrically connected to the emitter.

[0041] Alternatively, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) can be used as switching power semiconductor devices in power semiconductors 21 and 22. A MOSFET has three electrodes: a drain electrode, a source electrode, and a gate electrode. In the case of a MOSFET, a parasitic diode with a forward-biased direction from the drain electrode to the source electrode is provided between the source electrode and the drain electrode. Therefore, diode 38 is not required.

[0042] Each phase arm is constructed by electrically connecting the emitter and collector of the IGBT in series. Furthermore, in this embodiment, for simplicity, each IGBT in each phase's upper and lower arms is illustrated as a single power semiconductor; however, due to the large controlled current capacity, it is actually a configuration of multiple IGBTs electrically connected in parallel.

[0043] exist Figure 2 In the example shown, each upper and lower arm of each phase consists of three IGBTs. The collector of the IGBT 21 in the upper arm of each phase is electrically connected to the positive side of the battery 180, and the source of the IGBT 22 in the lower arm of each phase is electrically connected to the negative side of the battery 180. The midpoint of each arm of each phase (the connection between the emitter of the upper arm IGBT 21 and the collector of the lower arm IGBT 22) is electrically connected to the armature winding (stator winding) of the corresponding phase of the motors 200 and 202.

[0044] The control circuit 648 mounted on the control circuit board 646 and the transceiver circuit 644 mounted on the capacitor module 630 and connector board 642 are circuits commonly used in the first inverter device and the second inverter device. The aforementioned switching power semiconductor elements 21 and 22 operate according to the drive signals output from their respective drive circuits 652 and 656, by inputting to the power modules 610 and 620.

[0045] Drive circuits 652 and 656 constitute drive units for controlling corresponding inverter devices 610 and 620, generating drive signals for driving IGBT 21 based on control signals output from control circuit 648. The drive signals generated by drive circuits 652 and 656 are respectively output to the gates of the power semiconductor elements of the corresponding power modules 610 and 620. In drive circuits 652 and 656, six integrated circuits (IGBTs) are respectively provided to generate drive signals supplied to the gates of the upper and lower arms of each phase, and these six integrated circuits are configured as a block.

[0046] Control circuit 648 is the control unit of each inverter device 610 and 620. It is composed of a microcomputer that calculates control signals (control values) to activate (turn on / off) multiple switching power semiconductor elements. That is, the inverter device 600 equipped with control circuit 648 functions as a motor control device. Torque command signals (torque command values) from a higher-level control device, sensor outputs from current sensors 660 and 662, and sensor outputs from rotation sensors (not shown) mounted on motors 200 and 202 are input to control circuit 648. Based on these input signals, control circuit 648 calculates control values ​​and outputs control signals to drive circuits 652 and 656 to control the switching timing of power modules 610 and 620. Drive circuits 652 and 656 output drive signals based on these control signals to power modules 610 and 620.

[0047] The transceiver circuit 644, mounted on the connector substrate 642, is used to electrically connect the inverter device 600 to an external control device and to transmit and receive information with other devices via the communication line 174. The capacitor module 630 constitutes a smoothing circuit for suppressing DC voltage fluctuations caused by the switching action of the IGBT 21, and is electrically connected in parallel with the DC-side terminals of the first power module 610 and the second power module 620.

[0048] Figure 3 yes Figure 1 The rZ cross-sectional view of the 200 motor.

[0049] Motors 200 and 202 have largely the same construction, but the construction shown below does not need to be used in both motors 200 and 202, or it may only be used in one of them. Furthermore, the construction of motor 200 will be used as a representative example in the following explanation.

[0050] The stator 230 is housed inside the housing 212. The stator 230 has a stator core 232 and a stator winding 238. The stator winding 238 is a three-phase motor winding consisting of a U-phase coil, a V-phase coil, and a W-phase coil.

[0051] With shaft 218 as a reference, rotor 280 is rotatably held radially on the inner circumference of stator core 232 with a gap 222. Rotor 280 includes rotor core 282 fixed to shaft 218, permanent magnet 284, and non-magnetic cover plate 226.

[0052] The housing 212 has a pair of end supports 214 with bearings 216, and the shaft 218 is rotatably held by the bearings 216. A rotary transformer 224 is mounted on the shaft 218 to detect the pole position and rotational speed of the rotor 280. The output from this rotary transformer 224 is taken into… Figure 2In the control circuit 648 shown.

[0053] like Figure 2 As described above, the power module 610 performs a switching action based on a control signal input from the control circuit 648, converting the DC power supplied from the battery 180 into three-phase AC power. This three-phase AC power is then supplied to... Figure 3 The stator winding 238 shown generates a rotating magnetic field on the stator 230. The frequency of the three-phase alternating current is controlled based on the output value of the rotary transformer 224, and the phase of the three-phase alternating current relative to the rotor 280 is also controlled based on the output value of the rotary transformer 224.

[0054] The motor 200 is equipped with a protection function to ensure that each component does not exceed its heat resistance temperature. Examples of such protection methods include monitoring the actual temperature using a thermistor 244 (which acts as a temperature sensor) and monitoring an estimated temperature based on a temperature estimation calculation using a thermal circuit described later.

[0055] The protection method based on thermistor 244 involves directly mounting the thermistor 244 on the component to be protected to monitor the actual temperature. Thermistors 244 can be installed on each of the three phases (U, V, and W) of the stator winding 238, where heat generation is high, to measure the coil temperature, or one can be installed on each of two phases. Furthermore, considering cost and layout simplification for control, thermistors 244 can be installed on only one phase of the stator winding 238 where the highest temperature is likely to occur, to measure the coil temperature, or multiple thermistors can be installed on one phase. Especially when a star connection is used in the stator winding 238 wiring method, the thermistor 244 can be installed at the neutral point to measure the coil temperature. If temperature protection for each component is possible, multiple thermistors can also be installed on components other than the stator winding 238 for measurement. This description of the invention describes a motor protection method with only one thermistor 244 installed on the V phase.

[0056] Furthermore, since the stator winding 238 creates a temperature gradient within the component, higher-precision protection can be achieved by installing thermistors 244 at the locations where temperatures rise, provided the internal layout of the motor 200 allows. A method for protection based on an estimated temperature calculated using a thermal circuit assembly will be described later.

[0057] Figure 4 This is a schematic diagram of a thermal circuit used in a method for protection based on a temperature estimation calculation.

[0058] The temperature estimation value of the control circuit 648 is calculated by measuring the heat generated based on the current values ​​read by the current sensors 660 and 662 of the inverter device 600. Specifically, the control circuit 648 is a coil temperature estimation unit that, based on the current flowing through the three-phase motor winding 238, inputs the heat generated to each node of the thermal circuit 700, and estimates the temperature of the stator winding 238 and stator core 232 of the U-phase, V-phase, and W-phase based on the heat capacity set for each thermal resistance 706, 707, 708 and each node 701, 702, 703, 704.

[0059] The structure of the thermal circuit 700 is described below. The thermal circuit 700 is a thermal circuit consisting of U-phase winding node 701, V-phase winding node 702, W-phase winding node 703, stator core node 704, cooling source node 705, inter-winding thermal resistance 706 connecting U-phase winding node 701, V-phase winding node 702, and W-phase winding node 703, winding-stator core thermal resistance 707 connecting each phase winding node 701, 702, 703 and stator core node 704, and stator core-cooling source thermal resistance 708 connecting stator core node 704 and cooling source node 705.

[0060] In this embodiment, the thermal circuit 700 is a water-cooled system with water channels installed inside the housing. Therefore, the thermal circuit 700 is assembled with cooling source nodes 705 connected to stator core nodes 704. When using oil cooling to directly cool the stator windings, the cooling source nodes 705 are simply connected to the winding nodes 701-703 and the stator core nodes 704 of each phase. When using cooling sources other than water and oil cooling, the same operation can be performed by setting corresponding cooling source nodes 705 in the thermal circuit 700.

[0061] In this embodiment, the number of nodes to be calculated is minimized in order to suppress the control load as much as possible. However, if there is sufficient control capacity, the winding nodes 701-703 and the stator core node 704 can be further segmented to improve accuracy, or additional component nodes other than the winding nodes 701-703 and the stator core node 704 can be added. If there are other components that need to be protected, nodes can be added each time to expand the scope. However, the more items are calculated, the greater the control capacity becomes, so it is desirable to have only the minimum number of nodes necessary to protect.

[0062] The temperature estimation calculation using the thermal circuit 700 will be explained. Furthermore, motor 200 will be used as an example for explanation. The heat generated by motor 200 is the same as the loss obtained by subtracting the output of motor 200 from its input (heat generated by motor 200 = loss of motor 200). The loss set in the thermal circuit 700 uses a loss mapping diagram composed of torque and speed. Therefore, it is possible to retrieve the mapping diagram based on torque commands from the upper control device and speed read from the rotary transformer 224, or to calculate the loss using the current value read from the current sensor 660 installed on the inverter device 600.

[0063] When using a loss mapping diagram, the loss value can be calculated based on magnetic field analysis, or the measured loss can be set. The loss mapping diagram has the advantage of separating individual losses when using calculations such as magnetic field analysis, but it may produce discrepancies with actual measurements. Conversely, when using actual measurements, it has the advantage of using the actual losses generated, but based on values ​​read from various sensors, it has the disadvantage of only being able to separate copper losses generated in the stator winding 238 and other losses.

[0064] Therefore, the losses of each component can be calculated by leveraging the advantages of both methods. For example, the calculated loss ratio can be applied to actual measurements for loss separation, or the loss can be calculated solely through calculation by matching the measured results. Since the former method uses measured values, higher accuracy can be expected.

[0065] When using the current value read from the current sensor 660 installed on the inverter unit 600, the value read from the current sensor 660 can be used directly, or the value after averaging the accumulated current value or the root mean square value can be used. Furthermore, when the current sensor 660 is installed on only one or two phases, since the electrical phase difference of the three phases of the stator winding is 120°, the current values ​​of the other phases where the current sensor 660 is not installed can be estimated and calculated based on the angle information of the rotary transformer 224.

[0066] Alternatively, instead of directly using the value of the current sensor 660, the current can be allocated to three phases based on the commanded or actual values ​​of the d-axis and q-axis currents after the two-phase to three-phase conversion used in the control of motors 200 and 202, and the angle information of the rotary transformer 224. The copper loss value is then calculated based on the current value obtained in this way and the resistance value of the stator winding 238.

[0067] Regarding other losses such as iron losses, a mapping diagram for other losses such as iron losses can be provided, based solely on the aforementioned loss mapping diagram. Alternatively, the thermal resistance can be set to be relatively large to account for other losses such as iron losses. Furthermore, a simple mathematical formula for current can be incorporated. If the region included in the temperature estimation calculation is only the low-rotation region where other losses such as iron losses are small, then only copper losses can be considered. While estimation calculations can be performed with high accuracy considering other losses such as iron losses, it is preferable to make choices based on the control load.

[0068] The heat capacity set for each thermal resistance 706, 707, 708 and each node 701, 702, 703, 704 can be calculated based on the component's density, thermal conductivity, specific heat, and other physical properties. Alternatively, measured thermal resistance and heat capacity can be used, or values ​​matched based on measured temperatures can be set. However, for the amount of varnish on the fixed stator winding 238 and stator core 232, where the actual penetration degree is difficult to grasp, it is difficult to calculate all the heat capacities. Therefore, setting values ​​matched between measured and calculated values ​​can be expected to achieve higher accuracy. With the matched measured and calculated values, any value is acceptable depending on the temperature protection or the desired operating time before applying torque limiting at the same operating point. For example, if the calculated value is adjusted to match the temperature of the thermistor 244, then when combining protection based on thermistor 244 and protection based on temperature estimation calculation, there will be no temperature difference due to their switching, thus having the advantage of easily achieving satisfactory results.

[0069] Regarding the temperature calculation for each node, the temperatures of winding nodes 701, 702, 703, and stator core node 704 are calculated. However, in the case of water cooling, for example, where a water circuit is provided inside the housing, the temperature of the cooling source node 705 can be measured by a pump that circulates the LLC (Long Life Coolant) as cooling water, or by a water temperature sensor installed on the motor or inverter unit, or by a water temperature estimated from a temperature sensor installed for temperature protection in the power module. It can be fixed to any value as long as protection is possible. However, in this case, similar to the method described above, to avoid over-protection, it is preferable to use the actual water temperature as much as possible. Similarly, in the case of oil cooling based on ATF (Automatic Transmission Fluid), if a circulation device is provided, a temperature sensor can be installed on the circulation device, or a temperature sensor can be installed inside the motor 200, and it can also be set to a fixed value. Other cooling methods can also use temperature sensors, or have them set to a fixed value and assembled into the thermal circuit.

[0070] Temperature calculations at each node can achieve higher accuracy by directly using the measured temperature values. However, due to trade-offs in layout and cost, it is preferable to estimate based on fixed values ​​and other temperature sensors if there is sufficient capacity for overheat protection.

[0071] While minimizing the temperature estimation calculation cycle and maximizing accuracy is desirable when there are no issues with the control load, synchronizing the rotation frequency (cycle) of the motor 200 with the calculation cycle results in a state equivalent to no simulated rotation, potentially leading to malfunctions. Therefore, in order to create a sinusoidal current shape flowing in the stator winding 238 of the motor 200, it is preferable to set a cycle that allows for at least five calculations within one cycle of the current at the highest speed within the range where the temperature estimation calculation is performed.

[0072] As another method for estimating the temperature, the winding temperature can be estimated by monitoring the LLC temperature in the case of water cooling without assembling the thermal circuit 700, or by monitoring the ATF temperature in the case of oil cooling using ATF. However, since the temperature is not directly estimated, over-protection needs to be set.

[0073] Figure 5 This is a flowchart illustrating the use of thermistors in temperature protection as an existing technology.

[0074] In step S801, processing begins when the inverter device 600 is powered on. In step S802, the thermistor value is obtained at a time interval set by the control circuit 648 of the inverter device 600.

[0075] The thermistor value obtained in step S803 is used for the winding temperature, which is used for protection functions in the control system of the inverter device 600. In step S804, if the winding temperature exceeds the torque limit threshold, the control circuit 648 controls the power conversion device 600 to suppress the torque to a protective range that does not exceed the heat resistance temperature of the stator winding 238. The process ends in step S805, but continues as long as the power supply to the inverter device 600 is not turned on.

[0076] Since the heat generated by the stator winding 238 is proportional to the square of the three-phase AC current, and the three-phase AC current and torque are proportional, protection is typically achieved by reducing the torque command to a level that allows for continuous operation when the torque limit threshold is exceeded, thereby lowering the temperature of the stator winding 238. The torque command change rate should ideally be set considering the heat resistance temperature and the vehicle's operating conditions.

[0077] The existing technology has the advantage of providing protection using actual temperature when using only thermistor 244, but the problem is that if only one thermistor 244 can be installed due to layout constraints, and only one of the three phases is installed, it is difficult to provide protection.

[0078] Figure 5 The flowchart shown can also be applied to protection scenarios based solely on temperature estimation. In this case, Figure 5 The flowcharts differ only in that the thermistor value is obtained for temperature estimation calculation; the processing flowcharts are the same. The judgment of the torque suppression command in the temperature estimation calculation is the same as that of the protection based on thermistor 244. If the temperature estimation value of any of the three phases exceeds the torque limit threshold, the torque suppression command is executed to control the system in a manner that does not exceed the heat resistance temperature.

[0079] The temperature-based protection method can operate on all three phases separately, so it only requires the thermistor 244 to be installed on one phase, making it effective when the windings are not rotating (when a temperature deviation occurs in the three-phase windings). However, due to errors from current sensors, etc., if over-protection measures are taken, such as reducing the output of motors 200 and 202 without considering these errors, protection may fail. This would also adversely affect the output of motors 200 and 202.

[0080] Both protection based on thermistor 244 and protection based on temperature estimation calculation have advantages. Therefore, the main point of this invention is not to be limited to either one, but to solve the problem by applying both protection methods. As a result, it is possible to perform operation without over-protection over a wider output range than before.

[0081] Figure 6 This is a flowchart illustrating the combination of thermistor-based protection and temperature estimation-based protection, where the temperature difference of the three-phase estimated values ​​is used in the switching determination.

[0082] In step S801A, processing begins when the inverter device 600 is powered on. First, in step S807A, an estimated value for the phase winding is obtained to confirm whether its temperature difference is within a specified temperature range, i.e., below a specified threshold. This estimated value for the phase winding uses the temperature detected by the thermistor 244 at that moment as the initial value. If the estimated value is below the threshold, as a protection based on the thermistor 244, the value of the thermistor 244 is obtained again in step S802A, and this value is used to control the winding temperature in step S803A.

[0083] In this embodiment, the initial value of the estimated value when the temperature estimation operation is ON is used as the temperature of the thermistor 244. However, it is also possible to perform the estimation operation in the background during the protection period based on the thermistor 244, and switch from the value of the determination of the temperature at which the torque limit is applied to the estimated value when the protection method is switched. In this case, the temperature estimation operation may accumulate sensor error, so in order to improve accuracy, it is preferable to reset it after a certain period of time to return to the thermistor temperature 760.

[0084] On the other hand, in step S807A, if the temperature exceeds a threshold, as a protection based on temperature estimation calculation, a temperature estimation value is calculated in step S808A, and this calculated value is used for the winding temperature control in step S809A. The control circuit 648 determines whether protection is needed based on the adopted winding temperature value. If the torque limit threshold is exceeded, torque is suppressed in step S804A to perform temperature protection. This series of processes continues as long as the power supply to the inverter device 600 is not turned on.

[0085] In this way, by switching between the two protection methods at a specified threshold, the advantages of each protection method can be utilized. Even when there is a temperature difference between the three phases of the stator winding 238, protection can be provided even when only one or two phases of the thermistor 244 are installed in the three phases.

[0086] Furthermore, even when the thermistor 244 is installed in a three-phase configuration, the heat generated when the motor 200 is stopped (0 r / min) results in a loss that is up to twice that during rotation (since the peak current is √2 times the effective value, the copper loss is RI^2). Therefore, when protecting the motor solely with the thermistor 244, which has a time constant, a margin of safety is required compared to when it is rotating. However, the temperature estimation calculation can have either a time constant or not. That is, since the time constant can be arbitrarily set in the temperature estimation calculation, even when three thermistors 244 are installed, the margin of safety can be reduced by using the temperature estimation calculation at extremely low speeds, resulting in higher performance than previous temperature protection based solely on the thermistor 244.

[0087] Figure 7 This is a flowchart illustrating the combination of thermistor-based protection and temperature estimation-based protection, with the addition of a speed threshold.

[0088] The process begins when the inverter device 600 is powered on in step S801B. In step S806B, the rotational speeds of motors 200 and 202 are first read from the rotary transformer 224, and it is determined whether the read rotational speeds are above a specified threshold. In step S806B, if the rotational speed is below the threshold, the process transitions to protection based on a coil temperature estimation value. That is, it proceeds to step S808B, obtains the temperature estimation value, uses this value for the control winding temperature, and performs a temperature estimation calculation. Based on the winding temperature value used in step S804B, it is determined whether protection is required. If the torque limit threshold is exceeded, torque is suppressed to perform temperature protection. The process is completed in step 805B, but it continues as long as the inverter device 600 is powered on. This flowchart shows the process from step S807B onwards when the rotational speed is above the threshold in step S806B. Figure 7 The flowcharts are the same.

[0089] In this way, by setting a threshold for rotational speed, it is easy to divide the protection zones into those based on the thermistor 244 and those based on temperature estimation calculations. For example, by setting the initial value to the thermistor temperature when switching to temperature estimation calculations, error factors in temperature estimation calculations (such as current sensor errors) can be minimized, enabling overheat protection with higher accuracy.

[0090] Figure 8 This is a schematic diagram of a case where a thermistor is used solely for temperature protection and is installed on the V-phase winding.

[0091] Even when the thermistor 244 is installed on only one phase, it is verified whether temperature protection can be provided. Thermistor 244 is installed on the coil of phase V at the open-circuit side of the coil terminal, but as mentioned above, when the rotation of motors 200 and 202 is 0 rpm, a temperature difference is generated in the three phases due to the deviation of the three-phase current, which may prevent protection from being provided.

[0092] For example, in this case, the three-phase temperatures become unbalanced, but to provide protection, this can be largely addressed by lowering the torque limit ON threshold compared to when rotating. At 0 rpm, the torque is limited because it exceeds the torque limit ON threshold. However, upon restarting, the three-phase temperatures remain constant and unbalanced, so it is possible to exceed the protected operating temperature at the applied torque limit temperature.

[0093] use Figure 8 (a) through (d) further illustrate the use of thermistors solely for temperature protection control. Additionally, Figure 8 (a) to (d) represent states of working at the same time.

[0094] Figure 8 (a) indicates the operation of torque 750 and speed 751. Here, the torque command is constant (except as described later). Figure 8 (d) refers to the range where the winding temperature exceeds the torque limit ON threshold 761 but falls below the torque limit OFF threshold 762. Time t1 is the boundary between the transition of motors 200 and 202 from rotation to stop, and time t2 is the boundary between the transition of motors 200 and 202 from stop to rotation. The rotation speed of motors 200 and 202 gradually decreases from the rotating state in region A, thus reaching a stopped state in region B. Furthermore, region C represents the action of rotating again from the stopped state, returning to the original rotation speed.

[0095] Figure 8 (b) indicates Figure 8 The current in the three-phase winding during operation (a). In regions A and C of the rotating state, the U-phase current 752, V-phase current 753, and W-phase current 754 have a 120° electrical phase difference and flow in a sinusoidal waveform. In region B, the rotation stops when the V-phase current 753, for which the thermistor 244 is installed, reaches 0A. In region C, rotation resumes, returning to the state of sinusoidal current flow. Furthermore, the frequency of the current varies according to the rotational speed 751, but... Figure 8 In (b), in order to understand the state during rotation and when stopped, the detailed frequency changes corresponding to the rotational speed 751 are omitted.

[0096] Figure 8 (c) represents the heat of heat (copper loss). Figure 8 (c) represents the copper loss of the winding during rotation (755), the copper loss of the U-phase and W-phase windings during stop (756), and the copper loss of the V-phase winding during stop (757). In this curve, it is assumed that the heat generated at the peak current is 100W.

[0097] Since the value of copper loss is determined by the winding resistance and the square of the current, for example, if the heat generated at the peak of the sine wave is 100W, then the current in regions A and C during rotation is considered to be 50W based on the effective value of the sine wave.

[0098] In region B at the moment of stopping, the current value is fixed according to the current phase, so the heat generated by each winding is different. Figure 8 In case (c), when the current value of phase V is 0A, the current values ​​of phase U and phase W are the same. In this phase, the current of phase U and phase W winding 756 is 75W (assuming that the torque is limited to 45W during overheat protection). In addition, the current of phase V winding 757 is 0W, but since the phase U, phase V and phase W windings are in a mechanically close position, there is a temperature rise caused by heat transfer between the phases.

[0099] Figure 8 (d) indicates the temperature rise of the U-phase, V-phase, and W-phase windings due to the motor stopping, as well as the torque limit ON threshold 761 and torque limit OFF threshold 762. Additionally, in Figure 8 In (d), in region B where the temperature difference between the U and W phase windings (759) and the V phase winding (760) causes a stop, the torque limit ON threshold 761 and torque limit OFF threshold 762 are lowered compared to regions A and C, so that protection can be provided even when the three-phase temperatures are unbalanced.

[0100] like Figure 8 As shown in (d), in region B, due to the difference in heat generation when motors 200 and 202 are stopped, the temperatures of phases U and W do not cross the torque limit ON threshold 761 or the torque limit OFF threshold 762. Therefore, a temperature difference is generated between phases U and W and phase V.

[0101] If the temperature 760 of the thermistor 244 mounted on the V-phase winding being monitored exceeds the torque limit ON threshold 761, then the torque limit is applied; if it is below the torque limit OFF threshold 762, then the torque limit is lifted and the original torque command is returned.

[0102] If the temperature of each phase in observation zone A rises, the winding temperature (during rotation) 758 will be the same across all three phases since the heat generation of phases U, V, and W is the same. However, if zone B is entered, the torque limit ON threshold 761 corresponding to a rotational speed of 0 / min changes, so torque limiting is applied simultaneously with entering zone B. Thus, torque limiting ON and OFF are repeatedly applied between zones B.

[0103] If the motors 200 and 202 start rotating again after entering region C, the torque limit ON threshold 761 and torque limit OFF threshold 762 return to the thresholds for rotation in region A. Therefore, while maintaining the temperature difference of the three-phase windings, the torque limit becomes OFF.

[0104] However, in this case, during rotation in region C, with a temperature difference between the low temperature 760 of the V-phase winding and the high temperature 759 of the U-phase and W-phase windings, the torque limit becomes OFF. Therefore, when the temperature of the V-phase winding, where the thermistor is installed, reaches the torque limit ON threshold 761, the temperatures 759 of the U-phase and W-phase windings may exceed their heat resistance temperatures. That is, when rotation resumes, the three-phase temperatures become unbalanced.

[0105] Therefore, in region C, if the temperature difference between phase U and phase W and phase V cannot be eliminated, the motor rotation will start. After the torque limit is applied, the operating temperature may be exceeded. Therefore, if only a thermistor 244 is added to one phase, protection may not be possible.

[0106] Thus, while defining the torque limit ON threshold and torque limit OFF threshold during rotation and stopping allows for protection through their respective actions, protection becomes difficult when operating on complex curves involving repeated rotation and stopping. Furthermore, the switching of these thresholds causes torque fluctuations due to the torque limit becoming OFF at the moment of switching, making it an unstable operation and therefore undesirable.

[0107] As another method, instead of setting a torque limit ON or OFF threshold at the time of stop, a timer is used to apply torque limit if an arbitrary number of seconds have elapsed since the start of the stop, and then the torque limit is OFF after the arbitrary number of seconds has elapsed. However, in this case, temperature changes vary depending on the commanded torque, so the timer duration must be extended to ensure protection at all times, thus requiring an overprotected design.

[0108] As alternative methods, one could consider installing at least one thermistor 244 on each phase for ease of protection, or installing the thermistor 244 on the neutral coil electrically connected to the three phases. However, as mentioned above, if multiple thermistors 244 are used, the cost and layout may increase.

[0109] In addition, regarding the installation of the thermistor 244 to the neutral line, the neutral line is the part where the three phases are electrically connected. The burden of the layout when installing the thermistor 244 is reduced compared with the above method, but there is a certain distance mechanically. If the heat conduction of the components is taken into account, the temperature of the phase with higher temperature cannot be accurately measured. Therefore, there is a problem of setting a torque limit threshold for over-protection.

[0110] Figure 9 This is a schematic diagram of the operation in a case where protection based on a thermistor and protection based on temperature estimation calculation are combined, as one embodiment of the present invention.

[0111] exist Figure 9 (a) represents the shift in torque 750 and speed 751. Additionally, Figure 9 (a) is not merely an intention Figure 6 The flowchart also intends to... Figure 7 In the determination of step S806B, the protection method is selected based on the rotational speed, so the estimated ON threshold (rotational speed) 767 and the estimated OFF threshold (rotational speed) 768 are also shown.

[0112] exist Figure 9 In (b), it indicates that it is accompanied by Figure 9 The shifts in torque 750 and speed 751 in (a), the shifts in estimated temperatures of U and W phase windings 764 and estimated temperatures of V phase windings 765, represent the torque limit ON threshold 761 and torque limit OFF threshold 762.

[0113] exist Figure 9 In (c), it is shown that based on Figure 9 (b) The three-phase estimated temperature difference 766 and the estimated temperature OFF threshold (three-phase estimated temperature difference) 769. In addition, in this embodiment, the thermal resistance and thermal capacity of the temperature estimation calculation are adjusted in such a way that the thermistor temperature 752 and the three-phase estimated value become the same.

[0114] Combination Figure 7 The flowchart for Figure 9 Explain (a) to (c). Figure 9 In region D of (a), the rotational speed 751 is higher than the temperature estimation calculation ON threshold (rotational speed) 767. In this state, the protection determination, described later, is performed based on the temperature read from the thermistor 244. Regarding the read temperature, as... Figure 9 As shown in (b), within this range, the thermistor temperature 760 does not reach the torque limit ON threshold 761, so no torque limit is applied.

[0115] start Figure 9 The control circuit 648 of (a) uses a temperature estimation calculation ON threshold (speed) 767 to determine the protection method based on whether the motor speed read from the rotary transformer 224 is below this threshold. When the motor speed falls below a specified value at time t3, such as... Figure 7 As shown in step S806B, the protection is switched from using thermistor 244 to protection based on temperature estimation calculation.

[0116] In region E, the temperature estimation calculation begins, and the estimated temperatures of the three phases become the same during rotation. If the rotation speed becomes 0 r / min, a difference (resulting in a difference in heat generation) is generated in the current values ​​of the three phases, therefore... Figure 9 In the operation of phase (a) where the V phase rotates at a rotation angle of 0A at time t4, and the rotational speed changes from 751 to 0 r / min, as shown... Figure 9As shown in (b), the temperature of the V-phase winding is difficult to rise, while the slope of the temperature rise of the U-phase and W-phase windings is greater than during rotation. In the temperature estimation calculation, if the estimated temperature value of any one of the three-phase windings exceeds the torque limit ON threshold 761, a torque limit is applied, thus becoming an operation that applies a torque limit based on the estimated temperature values ​​764 of the U-phase and W-phase windings. Furthermore, the temperature difference between the V-phase and the U and W-phases at this time is... Figure 9 In (c), based on the difference in calorific value, the estimated three-phase temperature difference of 766 also shifts significantly.

[0117] Rotation resumes at time t5. In region F, the rotational speed of 751 exceeds the estimated temperature OFF threshold (rotational speed) of 768, but from... Figure 9 As shown in (c), the estimated three-phase temperature difference of 766 is greater than the estimated temperature OFF threshold (estimated three-phase temperature difference) of 769. Therefore, protection switching is not performed, and protection based on temperature estimation calculation continues.

[0118] At time t6, the estimated three-phase temperature difference of 766 falls below the estimated temperature OFF threshold (estimated three-phase temperature difference) of 769. Therefore, both the estimated speed and the estimated three-phase temperature difference are satisfied, meaning the estimated temperature difference is within the specified temperature range. Thus, at time t6, the protection system switches from temperature-based protection to thermistor-based protection. Figure 9 As shown in (b), this subsequently becomes the action of region G. Furthermore, if the rotational speed 751 subsequently falls below the temperature-estimated ON threshold (rotational speed) 767 again, i.e., below the specified rotational speed, the protection method switches from thermistor 244 to temperature estimation, and the protection method based on temperature estimation control and temperature estimation calculation is implemented again.

[0119] This invention provides overheat protection even under varying temperature conditions. Since the thermistor 244 only monitors the V-phase temperature, it is difficult to provide protection during stall. Temperature protection is implemented by replacing the thermistor 244 with a three-phase (U-phase, V-phase, W-phase) temperature estimation via the thermal circuit 700. This invention estimates the temperature of each component using the temperature estimation thermal circuit 700, adjusting the heat capacity and thermal resistance to match the actual temperature. Furthermore, it is configured to switch from temperature estimation to the temperature measurement of the thermistor 244 when the temperature difference between the estimated values ​​of the three phases is within a specified temperature range.

[0120] That is, protection based on thermistor 244 is implemented in the region above the specified rotational speed, and if the estimated temperature difference of the three phases is within the specified temperature difference, this temperature estimation control continues, and protection is maintained even after rotation resumes. Since the temperature estimation is calculated based on the temperatures of the three phases, therefore... Figure 8As shown in (c), motors 200 and 202 can be protected without changing the torque limit ON threshold.

[0121] Alternatively, the threshold for temperature estimation ON / OFF can be set only to the temperature difference between the estimated temperature value and the actual temperature. This involves continuously monitoring the thermistor temperature and the estimated temperature value. If there is no three-phase temperature difference with the estimated temperature value, the torque limit is switched ON / OFF based on the thermistor temperature. When the three-phase temperature difference with the estimated temperature value begins to appear, the torque limit is switched ON / OFF based on the estimated temperature value. In this case, as described above, considering the temperature shift during rotation that becomes the same as the thermistor temperature, and the error in the temperature estimation calculation, higher accuracy can be maintained if the estimated temperature value resets to the thermistor temperature value within a certain cycle.

[0122] Figure 10 This is a graph representing the torque-speed characteristics of a motor.

[0123] Typically, when a vehicle is to generate rotational force in the direction of travel, control is implemented such that the battery voltage is greater than the motor voltage, and adjustments are made to allow current to flow through the motor. Since the motor voltage is proportional to the rotational speed, weak magnetic field control is performed in a manner that does not exceed the battery voltage.

[0124] Regarding the threshold for switching between protection based on thermistor 244 and protection based on temperature estimation calculation, Figure 9 The temperature-estimated ON threshold (speed) 767 and temperature-estimated OFF threshold (speed) 768 shown in (a) are set to values ​​larger than the speed reading error of the rotary transformer 224, thus avoiding frequent switching of the protection method when operating near the threshold, which is therefore preferable. Although the accuracy depends on the value used for Figure 4 The configuration of the thermal circuit 700 for temperature estimation calculation varies, but in the low rotational region where copper loss dominates the heat generation of the motor, even a simple thermal circuit can easily maintain good accuracy. Therefore, a low speed threshold is preferred when reducing the load on the control.

[0125] For example, when the base speed of 770 is set to generate the highest speed in the maximum torque, considering that the higher the torque, the higher the copper loss and the higher the speed, the higher the iron loss, the judgment threshold that can be pulled out from the temperature estimation calculation even when the vehicle speed is 10-20km / h in congestion can also be set to below the motor speed or below the torque value.

[0126] Furthermore, the threshold value for the three-phase estimated temperature difference is set as small as possible based on the error of the current sensor used for calculation or the error of the temperature estimation calculation. Since the error with the thermistor during switching is reduced, this is preferred.

[0127] Thus, as a switching method, by setting the rotational speed and the estimated temperature difference between the three phases, protection can be provided even if only one phase is equipped with the thermistor 244. Furthermore, even with one thermistor 244 installed in each of the three phases, temperature protection with higher accuracy can be provided when the circuit stops.

[0128] The above embodiments are examples of embedded magnet type motors 200 and 202 in which magnets are embedded in the rotor, but are not limited to this. Any motor that uses a surface magnet type with magnets attached to the rotor surface, or a motor that utilizes only reluctance torque due to the rotor structure that does not use permanent magnets, or a motor that requires temperature protection such as a sensor, can be used for the protection function.

[0129] According to the above-described embodiment of the present invention, the following effects are achieved.

[0130] (1) The motor control device 600 is a motor control device for controlling the motor 200 (202), which includes: a three-phase motor winding 238, which is composed of a U-phase coil, a V-phase coil and a W-phase coil; and a thermistor 244, which measures the temperature of any one or two coils in the three-phase motor winding 238. The motor control device 600 includes a coil temperature estimation unit (control circuit 648), which calculates the estimated temperature of the U-phase coil, the V-phase coil and the W-phase coil based on the current value flowing through the three-phase motor winding 238. When the difference between the estimated temperatures of the three-phase motor winding 238 is greater than a predetermined value, the motor control device controls the motor 200 (202) based on the estimated temperature of the three-phase motor winding 238. When the difference between the estimated temperatures of the three-phase motor winding 238 is less than or equal to a predetermined value, the motor control device controls the motor 200 (202) based on the measured value of the thermistor 244. In this way, even without installing sensors on the U, V, and W phases of the motor, a motor control device capable of providing three-phase overheat protection can still be provided.

[0131] (2) When the difference between the estimated temperatures of the three-phase motor windings 238 of the motor control device 600 is below a specified value and the speed of the motor 200 (202) is above a specified speed, the motor 200 (202) is controlled based on the measured value of the thermistor 244. In this way, it is easy to divide the protection areas based on the thermistor 244 and the protection areas based on temperature estimation calculation.

[0132] (3) When the speed of the motor 200 (202) is less than the specified speed, the motor control device 600 controls the motor 200 (202) based on the estimated temperature of the three-phase motor windings 238, even if the difference between the estimated temperatures of the three-phase motor windings 238 is below a specified value. In this way, it is easy to divide the protection areas based on the thermistor 244 and the protection areas based on temperature estimation calculation.

[0133] (4) A motor control method comprising: a three-phase motor winding 238 consisting of a U-phase coil, a V-phase coil, and a W-phase coil; and a thermistor 244 for measuring the temperature of any one or two coils in the three-phase motor winding 238. The motor control method calculates the estimated temperatures of the U-phase coil, the V-phase coil, and the W-phase coil based on the current flowing through the three-phase motor winding 238. If the difference between the estimated temperatures of the three-phase motor winding 238 is greater than a predetermined value, the motor 200 (202) is controlled based on the estimated temperatures of the three-phase motor winding 238. If the difference between the estimated temperatures of the three-phase motor winding 238 is less than a predetermined value, the motor 200 (202) is controlled based on the measured value of the thermistor 244. Therefore, the motor control device can achieve three-phase overheat protection even if no sensors are installed on any of the U-phase, V-phase, and W-phases of the motor 200 (202).

[0134] The above-mentioned deletions, substitutions of other structures, and additions of other structures are all possible without departing from the technical concept of the invention, and such methods are also included within the scope of the present invention.

[0135] Symbol Explanation

[0136] 21…Power Semiconductors (Upper Arm)

[0137] 22…Power Semiconductors (Lower Arm)

[0138] 38… Diode

[0139] 100… vehicles

[0140] 110…front tire

[0141] 120… engine

[0142] 124… Engine Control Unit

[0143] 130… transmission

[0144] 134…Transmission control unit

[0145] 160… Differential gear

[0146] 170…Integrated Control Device

[0147] 174… communication lines

[0148] 180… battery

[0149] 184…Battery Control Device

[0150] 200… First Motor

[0151] 202…Second Motor

[0152] 600… Inverter device

[0153] 212…shell

[0154] 214…End support

[0155] 216…bearing

[0156] 218… axis

[0157] 222…gap

[0158] 224… Rotary Transformer

[0159] 226…cover plate

[0160] 230…Stator

[0161] 232…Stator core

[0162] 236… teeth

[0163] 237… slot

[0164] 238…Stator winding

[0165] 244… Thermistor

[0166] 280… rotor

[0167] 282… rotor core

[0168] 284… permanent magnets

[0169] 600… Inverter device

[0170] 610…Power module of the first inverter unit

[0171] 620… Power module of the second inverter unit

[0172] 630… Capacitor Module

[0173] 642… Connector substrate

[0174] 644… Transceiver Circuit

[0175] 646…Control Circuit Board

[0176] 648… control circuit

[0177] 650…Driver Circuit Board

[0178] 652…First Drive Circuit

[0179] 654…Driver Circuit Board

[0180] 656…Second Drive Circuit

[0181] 660… First motor current sensor

[0182] 662…Second Motor Current Sensor

[0183] 700…heat circuit

[0184] 701…U-phase winding node

[0185] 702…V phase winding node

[0186] 703…W phase winding node

[0187] 704…Stator core node

[0188] 705…Cooling Source Node

[0189] 706…Inter-winding thermal resistance

[0190] 707… Thermal resistance between winding and stator core

[0191] 708… Thermal resistance between stator core and cooling source

[0192] 750…torque

[0193] 751… RPM

[0194] 752…U-phase current

[0195] 753…V phase current

[0196] 754…W phase current

[0197] 755… Copper loss of the winding (during rotation)

[0198] Copper losses of phases 756…U and W (when stopped)

[0199] Copper loss of 757…V phase winding (when stopped)

[0200] 758…Temperature of the winding (during rotation)

[0201] 759…U and W phase winding temperatures (during rotation)

[0202] Temperature of the 760…V phase winding (during rotation)

[0203] 761… Torque Limit ON Threshold

[0204] 762… Torque Limit OFF Threshold

[0205] 763… Thermistor temperature

[0206] 764…Estimated temperatures of U and W phase windings

[0207] 765…V phase winding temperature estimate

[0208] 766…Estimated three-phase temperature difference

[0209] 767…Estimated ON threshold temperature (speed)

[0210] 768…Estimated OFF threshold temperature (speed)

[0211] 769…Estimated OFF threshold temperature (estimated temperature difference between three phases)

[0212] 770… base speed.

Claims

1. A motor control device for controlling a motor, The motor has the following features: The three-phase motor winding consists of a U-phase coil, a V-phase coil, and a W-phase coil; and A thermistor, used to measure the temperature of any one or two coils in the three-phase motor windings. The motor control device is characterized by having a coil temperature estimation unit. This unit calculates the losses of the three-phase motor windings as heat generation based on the current flowing through them, inputs this heat generation to each node of the thermal circuit, and calculates the estimated temperatures of the U-phase coil, the V-phase coil, and the W-phase coil based on the thermal resistance and the set heat capacity of each node. Each node of the thermal circuit corresponds to a winding of the three-phase motor and a stator core, respectively. If the difference between the estimated temperatures of the three-phase motor windings is greater than a specified value, the motor control device controls the motor based on the estimated temperatures of the three-phase motor windings. When the difference between the estimated temperatures of the three-phase motor windings is below the specified value, the motor control device controls the motor based on the measured value of the thermistor.

2. The motor control device according to claim 1, characterized in that, When the difference between the estimated temperatures of the three-phase motor windings is below the specified value and the motor speed is above the specified speed, the motor control device controls the motor based on the measured value of the thermistor.

3. The motor control device according to claim 2, characterized in that, Even if the difference between the estimated temperatures of the three-phase motor windings is below the estimated temperature of the three-phase motor windings when the motor speed is less than the specified speed, the motor control device controls the motor based on the estimated temperature of the three-phase motor windings.

4. A method for controlling a motor, wherein the motor comprises: The three-phase motor winding consists of a U-phase coil, a V-phase coil, and a W-phase coil; and A thermistor, used to measure the temperature of any one or two coils in the three-phase motor windings. The motor control method is characterized in that... The losses of the three-phase motor windings are calculated based on the current flowing through them, and this loss is used as the heat generated. This heat is input to each node of the thermal circuit. Based on the thermal resistance and the set heat capacity of each node, the estimated temperatures of the U-phase coil, the V-phase coil, and the W-phase coil are calculated respectively. Each node of the thermal circuit corresponds to a winding of the three-phase motor and a node of the stator core. If the difference between the estimated temperatures of the three-phase motor windings is greater than a specified value, the motor is controlled based on the estimated temperatures of the three-phase motor windings. When the difference between the estimated temperatures of the three-phase motor windings is below the specified value, the motor is controlled based on the measured value of the thermistor.

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