JP7257845B2 - Rotor temperature estimator and rotor temperature estimation system for induction motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rotor temperature estimator and a rotor temperature estimation system for an induction motor, and more particularly to improving the accuracy of rotor temperature estimation.

Patent Literature 1 describes a device for estimating the rotor temperature of an induction motor. This device calculates the slip frequency correction value based on the temperature change of the secondary resistance of the induction motor, and based on the d-axis current command value, the q-axis current command value, and the slip frequency correction value used for vector control. The secondary resistance estimated value R2S is calculated, and the rotor temperature T2S is calculated from the reference temperature, the measured value of the secondary resistance at the reference temperature, and the secondary resistance estimated value R2S.

JP 2006-280142 A

The rotor temperature estimating device described in Patent Document 1 uses the secondary resistance estimated value R2S derived from the current value in order to calculate the rotor temperature T2S. In this estimating device, the sensitivity of the current value is high in the calculated value of the rotor temperature T2S. This current value has a fast response and is susceptible to noise. As a result, the estimated value of the rotor temperature oscillates, or the temperature rises or falls at a speed that cannot actually occur, and the estimation accuracy of the rotor temperature may deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to improve the accuracy of rotor temperature estimation in a rotor temperature estimator and a rotor temperature estimation system for an induction motor.

A rotor temperature estimator for an induction motor according to the present invention provides, for an induction motor, a motor rotation speed, a detected value of stator coil temperature, a control command value or detected value of a stator coil current value, a slip frequency, and a rotor temperature. A motor loss calculator that receives the previous estimated value and calculates the loss generated in the stator and the rotor, the calculated value of the loss generated in the stator and the rotor, the detected value of the stator coil temperature, and the induction motor a rotor temperature estimating unit that receives a detected value of the temperature of outside air contacting the outside of the frame and obtains an estimated value of the rotor temperature from a model that is set using thermal energy balance.

Further, a rotor temperature estimation system for an induction motor according to the present invention includes: a rotor temperature estimator for an induction motor; a rotation speed sensor for detecting the motor rotation speed; a coil temperature sensor for detecting the stator coil temperature; and an outside air temperature sensor that detects the temperature of the rotor, and signals detected by the rotational speed sensor, the coil temperature sensor, and the outside air temperature sensor are sent to the rotor temperature estimator.

According to the rotor temperature estimator and rotor temperature estimating system for an induction motor according to the present invention, when the loss generated in the stator and rotor is calculated using the current value and the estimated value of the rotor temperature is obtained using the calculated value, First, an estimate of the rotor temperature is obtained from a model set using the thermal energy balance. As a result, in the estimated value of the rotor temperature, the sensitivity of the heat capacity of related elements such as the rotor-side member is increased, so that the fluctuation of the current value, which has a fast response and is susceptible to noise, is less likely to be affected. Therefore, unlike the configuration described in Patent Document 1, in which the rotor temperature is estimated so as to increase the sensitivity of the current value in the estimated value of the rotor temperature, the estimation accuracy of the rotor temperature can be improved.

1 is a configuration diagram of an induction motor to which a rotor temperature estimation system according to an embodiment of the invention is applied; FIG. 1 is a configuration diagram of a rotor temperature estimation system of an embodiment; FIG. 3 is a block diagram showing the configuration of a rotor temperature estimator that constitutes the rotor temperature estimation system of the embodiment; FIG. 2 is a diagram showing an example of a thermal circuit model for the configuration of FIG. 1 used in the rotor temperature estimator of the embodiment; FIG. FIG. 4 is a diagram showing the tendency of the thermal resistance of air 0, 1, 2 to change depending on the number of motor revolutions; FIG. 7 is a configuration diagram of a rotor temperature estimation system of another example of the embodiment; FIG. 4 is a diagram corresponding to FIG. 3 in another example of the embodiment; FIG. 10 is a diagram showing changes in motor rotation speed over time in an experiment conducted to confirm the effects of the embodiment; FIG. 3 is a diagram comparing changes in the estimated value of the rotor temperature in the rotor temperature estimation system of FIG. 2 with changes in the measured value (true value) of the rotor temperature obtained in an experiment; FIG. 10 is a graph comparing changes in the estimated value of the rotor temperature with changes in the measured value (true value) of the rotor temperature obtained in an experiment in the rotor temperature estimation system of another example of the embodiment; FIG. 9 is a block diagram showing a configuration of part of a control device in a rotor temperature estimation system of another example of the embodiment;

Embodiments of the present invention will be described below with reference to the drawings. When a plurality of embodiments, modifications, and the like are included below, they can be implemented in appropriate combinations. In the following description, the same reference numerals are assigned to the same elements in all the drawings. A rotor temperature estimator and a rotor temperature estimation system for an induction motor will be described below, but the induction motor may be a motor generator having the function of a generator.

FIG. 1 is a configuration diagram of an induction motor 50 to which the rotor temperature estimation system 10 (FIG. 2) of the embodiment is applied. The induction motor 50 includes a stator 53 fixed to the first frame 51 and the second frame 52 and a rotor 60 . Although the case where the frame of the induction motor 50 is divided into two will be described below, the number of frames is not limited.

The stator 53 has a stator coil 55 attached to an annular stator core 54 . The stator coil 55 includes three-phase coils of U-phase, V-phase, and W-phase. The stator coil 55 may be configured to have multi-phase coils other than three-phase coils. In FIG. 1, the spaces 70, 71 within each frame 51, 52 are indicated by fine sand.

A part of the 3-phase coil is drawn out from the stator core 54 and connected to a 3-phase terminal (not shown). The three-phase terminals are connected to three-phase wires (not shown) connected to an inverter (not shown) on the power supply side. The inverter is controlled according to the torque command value by a control device 40 (FIG. 2), which will be described later.

The rotor 60 is arranged radially inwardly facing the stator 53 and fixed to the outer peripheral surface of the rotating shaft 63 . The rotating shaft 63 is rotatably supported by the first frame 51 and the second frame 52 via bearings S<b>1 and S<b>2 , and the portion projecting outward from the first frame 51 is connected to the load 65 . As a result, the load 65 is driven by the rotation of the rotor 60 .

Rotor 60 is a squirrel cage rotor. Specifically, the rotor 60 includes a rotor core made of a magnetic material fixed to a rotating shaft 63, a plurality of conductor bars inserted into holes provided at a plurality of positions in the rotor core in the circumferential direction, and ends of the plurality of conductor bars. A pair of end rings short-circuited by connecting the parts to each other at both ends in the axial direction of the rotor core. The conductor bars and end rings are made of electrically conductive material.

In FIG. 1 , the rough sand portion indicates the surrounding space (outside air portion) 72 of the induction motor 50 , and the diagonal lattice portion indicates the space 73 between the inner peripheral surface of the stator 53 and the outer peripheral surface of the rotor 60 . . As will be described later, the air resistance between the air in the space 73 (air 0) and the air in the spaces 70 and 71 in the frames 51 and 52 (air 1 and 2) changes according to the motor rotation speed.

During operation of the induction motor 50, the stator coil 55 is energized to generate a rotating magnetic field in the stator 53, and the rotating magnetic field causes an induced current (rotor secondary current) to flow through the conductor bars. An electromagnetic force acting between the induced current and the rotating magnetic field causes each conductor bar to generate a rotating force in a predetermined direction. As a result, the rotor 60 rotates around the center of the rotating shaft 63 . The induction motor 50 may have a wound rotor in which a three-phase coil is arranged in the rotor core.

Such an induction motor 50 is used by being mounted on a vehicle such as an electric vehicle or a hybrid vehicle. A hybrid vehicle includes an engine and a motor as drive sources for the wheels. For example, the induction motor 50 is a driving motor, and drives the wheels by transmitting power from the driving motor to the wheels.

Since the rotor 60 rotates in such an induction motor 50, it is difficult to measure the temperature of the rotor 60 directly. For this reason, the rotor temperature estimating system 10 (FIG. 2) of the embodiment uses the coil temperature detection value of the stator coil 55 or the like to accurately estimate the temperature of the rotor 60 without directly detecting the temperature of the rotor 60. estimated to . Further, unlike the rotor temperature estimating device described in Patent Document 1, the rotor temperature estimating system 10 has a fast response in the estimated value of the rotor temperature. , was considered to improve the estimation accuracy of the rotor temperature.

FIG. 2 is a configuration diagram of the rotor temperature estimation system 10. As shown in FIG. FIG. 3 is a block diagram showing the configuration of the control device 40 that constitutes the rotor temperature estimation system 10. As shown in FIG. The rotor temperature estimation system 10 may be referred to as an estimation system 10 below. The estimation system 10 includes a control device 40 , a rotation speed sensor 30 , a coil temperature sensor 31 and an outside air temperature sensor 32 . Control device 40 corresponds to a rotor temperature estimator.

The control device 40 has an arithmetic processing unit such as a CPU and a storage unit such as a memory. The control device 40 also has a motor loss calculator 42 and a rotor temperature estimator 41 . Rotation speed sensor 30 detects the rotation speed of rotor 60 constituting induction motor 50 as motor rotation speed N, and transmits the detection signal to control device 40 . Rotation speed sensor 30 may be configured by a resolver that detects the rotation angle of rotor 60 . Coil temperature sensor 31 detects a coil temperature Tcoil of stator coil 55 and transmits the detection signal to control device 40 . The coil temperature Tcoil corresponds to the stator coil temperature. The outside air temperature sensor 32 detects the temperature of the outside air contacting the outside of the first frame 51 and the second frame 52 of the induction motor 50 as the outside air temperature Tair3 around the induction motor 50, and sends the detection signal to the control device 40. Send.

Further, an external control device (not shown) receives a detected value of an operation amount for instructing acceleration from an acceleration indicating sensor such as an accelerator pedal sensor of the vehicle, and calculates a torque command value TR according to the input. be. The external control device may calculate the torque command value TR from the operation amount detection value for instructing acceleration and the detection value of the vehicle speed sensor. Further, the operation amount detection value or the like for instructing acceleration may be directly input to the control device 40, and the control device 40 itself may calculate the torque command value TR. In the external control device, control command values for the coil current Is and the slip frequency ωs are calculated based on the torque command value TR and the motor rotation speed N.

The coil current Is is a motor primary current and corresponds to a stator coil current value given to the induction motor 50 as a control command value. The external control device may calculate the effective value of the coil current of one predetermined phase as the coil current Is, or may calculate the effective value of the coil currents of the three phases. Control command values for the coil current Is and the slip frequency ωs are input to the control device 40 from an external control device.

As shown in FIG. 3, the motor loss calculator 42 receives the detected value of the motor rotation speed N, the detected value of the coil current Is, the slip frequency ωs, and the detected values of the coil temperature Tcoil. Further, the motor loss calculator 42 also receives an estimated value (previous estimated value) of the rotor temperature Trot in the previous rotor temperature estimation from the output side of the rotor temperature estimator 41 described later.

As the coil current Is, instead of the control command value, a detected value detected by a current sensor may be input to the motor loss calculator 42 . At this time, the control device 40 calculates the effective value of the coil current of the predetermined phase based on multiple detections of the coil current of one predetermined phase input from the current sensor. A plurality of current detection values detected at predetermined time intervals in the coil current of the predetermined phase are used for the calculation of the effective value. For example, the effective value of the U-phase coil current is calculated from the root mean square of a plurality of current detection values of the U-phase coil current Iu detected at predetermined time intervals. The calculated value of the effective value of the coil current of the predetermined phase is substantially the effective value of the coil current of the three phases. Then, the effective value of the coil current of the predetermined phase may be input to the motor loss calculator 42 as the coil current Is.

The motor loss calculator 42 calculates the loss generated in the stator 53 from the detected value of the motor rotation speed N, the detected value of the coil current Is, the slip frequency ωs, the detected value of the coil temperature Tcoil, and the previous estimated value of the rotor temperature Trot. , the stator iron loss Loss_s1 and the stator copper loss Loss_s2, and the rotor loss Loss_r generated in the rotor 60 are calculated.

As shown in FIG. 3, the rotor temperature estimator 41 receives the detected value of the coil temperature Tcoil, the detected values of the stator iron loss Loss_s1, the stator copper loss Loss_s2, the rotor loss Loss_r, and the outside temperature Tair3. Based on these inputs, the rotor temperature estimator 41 obtains an estimated value of the rotor temperature Trot by a thermal circuit model set using the thermal energy balance.

A specific example of the thermal circuit model, which is the target model, will be described with reference to FIG. FIG. 4 shows an example of a thermal circuit model for the configuration of FIG. 1 used in the estimation system 10. In FIG. Further, assuming that the temperature of the rotor core and the conductor bars as the secondary conductors in the rotor 60 and the temperature of the rotating shaft 63 are equal to each other, these elements are combined to form the rotor-side member 64 .

In FIG. 4, the air in the space 73 indicated by the oblique grid portion in FIG. Also, the air in the surrounding space 72 indicated by the rough sandy part in FIG. Temperatures Tsta, Tfr1, Tfr2, Tload, Tcoil, and Trot of stator core 54, first frame 51, second frame 52, load 65, stator coil 55, and rotor-side member 64, and temperature Tair0 of air 0, 1, 2, and 3 , Tair1, Tair2, and Tair3 are connected by thermal resistors 75 to form a thermal circuit model.

The thermal circuit model shown in FIG. 4 is divided into a stator core 54, a stator coil 55, a rotor-side member 64, a first frame 51, a second frame 52, and a load 65 as a plurality of thermally connected elements.

The thermal resistance of air 0, 1, 2 changes with the motor rotation speed N. Specifically, as schematically shown in FIG. 5, between the motor rotation speed N and the thermal resistance of air 0, 1, 2, the thermal resistance decreases as the motor rotation speed N increases, and the motor rotation speed There is a relationship that the smaller the N, the greater the thermal resistance. As a result, the heat resistance 75 circled in FIG. Therefore, the values related to the thermal resistance of the air 0, 1, 2 change according to the motor rotation speed N.

Equation (1) is obtained from the thermal circuit model of FIG.

Here, matrices A and B are coefficient matrices. Matrix C is represented by Equation (2).

The matrix A contains parameters whose values change according to the motor rotation speed N, because the thermal resistances of the air 0, 1, and 2 change according to the motor rotation speed N. FIG.

The rotor temperature estimator 41 shown in FIG. 3 uses a state equation as a relational expression based on Equations (1) and (2) to estimate the rotor temperature Trot. Specifically, the rotor temperature estimator 41 uses an observer represented by Equation (3).

In Expression (3), x and y representing estimated values are superscripted with a chevron (hat). Also, at x, the temperature Trot of the rotor-side member 64 (FIG. 4) is the estimated value. u and y are composed of known values input to the rotor temperature estimator 41 (FIG. 3). F represents the gain of the observer. Further, the equation (3) used in the rotor temperature estimator 41 uses, as the parameter component of the matrix A, a value calculated at an arbitrary number of rotations below the predetermined number of rotations of the motor rotation number N.

Then, the gain F is designed so that yy (hat) asymptotically converges to 0 in the equation (3) used in the rotor temperature estimator 41 . The rotor temperature estimator 41 calculates a rotor temperature Trot that matches the temperature of the rotor-side member 64 (FIG. 4) from the equation of state shown in Equation (3). Thereby, the rotor temperature estimator 41 estimates the rotor temperature Trot using the observer designed by the thermal circuit model. Note that the rotor temperature estimator 41 may estimate the rotor temperature using a thermal circuit model without using an observer.

According to the estimation system 10 described above, the current value is used to calculate the loss generated in the stator 53 and the rotor 60, and the calculated value is used to obtain the estimated value of the rotor temperature Trot. An estimated value of the rotor temperature Trot is obtained from the thermal circuit model set by As a result, in the estimated value of the rotor temperature Trot, the sensitivity of the heat capacity of related elements such as the rotor-side member 64 is increased, so that the fluctuation of the current value, which has a fast response and is susceptible to noise, is less likely to be affected. Therefore, unlike the configuration described in Patent Document 1 in which the rotor temperature is estimated so that the sensitivity of the current value is high in the estimated value of the rotor temperature, it is possible to improve the estimation accuracy of the rotor temperature Trot. This makes it possible to improve the controllability of the induction motor 50 by using the estimated value of the rotor temperature Trot. Furthermore, by using the estimation system 10 as a motor protection device that performs control such as stopping the induction motor 50 when the rotor 60 exceeds the allowable temperature, the protection function can be enhanced.

FIG. 6 is a configuration diagram of a rotor temperature estimation system 10a of another example of the embodiment. FIG. 7 is a diagram corresponding to FIG. 3 in another example of the embodiment. In the configuration of this example, unlike the configuration shown in FIGS. 44 and a switching unit 45 . The switching unit 45 switches between the low rotation speed side rotor temperature estimation unit 43 and the high rotation speed side rotor temperature estimation unit 44 according to the motor rotation speed.

As shown in FIG. 7, the rotor temperature estimator 43 on the low rotation speed side and the rotor temperature estimator 44 on the high rotation speed side store the detected value of the motor rotation speed N, the detected value of the coil temperature Tcoil, the stator iron loss Loss_s1, and the stator iron loss Loss_s1. Detected values of copper loss Loss_s2, rotor loss Loss_r, and outside air temperature Tair3 are input. Each of the rotor temperature estimating units 43 and 44 obtains an estimated value of the rotor temperature Trot from these inputs using a thermal circuit model set using the thermal energy balance. Specifically, the low rotation speed side rotor temperature estimation unit 43 and the high rotation speed side rotor temperature estimation unit 44 are prepared according to the motor rotation speed range of the induction motor 50 .

The air resistance between the air in the space 73 shown in FIG. 1 (air 0) and the air in the spaces 70 and 71 in the frames 51 and 52 (air 1 and 2) changes according to the motor rotation speed. Correspondingly, in the configuration of this example, the values of the thermal model are changed according to the reference motor rotation speed used for designing the rotor temperature estimating units 43 and 44 . Specifically, in the configuration of this example, each of the thermal models used in the rotor temperature estimating units 43 and 44 is based on the thermal resistance of the air between the rotor and the stator according to the reference motor rotation speed. Value has changed. Equation (3) used in the low-rotation-speed-side rotor temperature estimating unit 43 uses, as parameters of the matrix A, values calculated at an arbitrary rotation speed of the motor rotation speed N that is equal to or lower than a predetermined rotation speed. In addition, the numerical formula (3) used in the high rotation speed side rotor temperature estimator 44 uses values calculated at an arbitrary rotation speed at which the motor rotation speed N exceeds a predetermined rotation speed for the components of the matrix A as parameters. The elements of matrix A are not changed in each of low-speed rotor temperature estimator 43 and high-speed rotor temperature estimator 44 . As a result, part of the values in the relational expression representing the thermal circuit model in FIG. The rotor temperature estimator 44 and the rotor temperature estimator 44 are mutually changed according to the motor rotation speed N as a reference.

The gain F is designed so that yy (hat) asymptotically converges to 0 in the equation (3) used for each rotor temperature estimator 43,44. Thereby, the gain F is changed according to the change of the matrix A. Each of the rotor temperature estimators 43 and 44 calculates a rotor temperature Trot that matches the temperature of the rotor-side member 64 (FIG. 4) from the equation of state shown in Equation (3). Thereby, each rotor temperature estimator 43, 44 estimates the rotor temperature Trot using the observer designed by the thermal circuit model. Further, in the thermal circuit model, the thermal resistance of the air 0 between the rotor 60 and the stator 53 is changed between the rotor temperature estimating units 43 and 44 according to the motor rotation speed N. FIG. The rotor temperature estimating units 43 and 44 may estimate the rotor temperature using a thermal circuit model without using an observer.

Further, the switching unit 45 is selectively connected to the output sides of the low-speed rotor temperature estimating unit 43 and the high-speed rotor temperature estimating unit 44 . The switching unit 45 uses the low-speed rotor temperature estimating unit 43 when the motor speed N is equal to or less than a predetermined speed, and uses the high-speed rotor temperature estimating unit 43 when the motor speed N exceeds the predetermined speed. 44 is used, the rotor temperature estimating units 43 and 44 used for estimating the rotor temperature are switched.

According to the configuration of this example, the estimation system 10 switches the rotor temperature estimation units 43 and 44 according to the low rotation speed side rotor temperature estimation unit 43 and the high rotation speed side rotor temperature estimation unit 44, and the motor rotation speed N. and a switching unit 45 . As a result, the rotor temperature Trot can be estimated more accurately when the motor rotation speed N changes. Although there is almost no opportunity for the actual motor rotation speed N to completely match the rotation speed in the design of each rotor temperature estimator 43, 44, the rotor temperature Trot can be estimated due to the robustness of the observer.

Furthermore, each rotor temperature estimator 43, 44 of the estimation system 10 estimates the rotor temperature Trot using an observer designed with a thermal circuit model. Further, in the thermal circuit model, the thermal resistance of the air 0 between the rotor 60 and the stator 53 is changed according to the motor rotation speed N in the design. As a result, the rotor temperature Trot can be estimated with higher accuracy using the air thermal resistance that varies with the motor rotation speed N. Other configurations and actions in this example are the same as those in FIGS.

FIG. 8 is a diagram showing changes over time in the motor rotation speed N in an experiment conducted to confirm the effects of the embodiments of FIGS. 1 to 5 and the embodiments of FIGS. 6 and 7. FIG. . In the experiment, the induction motor 50 was rotated at a constant number of revolutions less than the predetermined number of revolutions at time 0- _t1 , and the number of revolutions was switched at time _t1 to rotate the induction motor 50 at a constant number of revolutions exceeding the predetermined number of revolutions. rotated.

FIG. 9 is a diagram comparing changes in the estimated value of the rotor temperature Trot in the estimation system 10 of the embodiment of FIGS. be. As shown in FIG. 9, the rotor temperature estimator 41 was able to estimate the rotor temperature Trot with high accuracy relative to the true value when the motor rotation speed N during time 0- _t1 was less than the predetermined rotation speed. In the embodiment, the estimated value of the rotor temperature Trot is determined by a thermal circuit model set using the balance of thermal energy. Unlike the configuration described in Document 1, it is possible to improve the estimation accuracy of the rotor temperature Trot. On the other hand, in the configuration of this example, when the thermal resistance of air changes with the actual motor rotation speed N, the rotor temperature is estimated using a model represented by one motor rotation speed N below a predetermined rotation speed. As a result, as indicated by the portion surrounded by the broken line frame α in _FIG . is gradually spreading.

FIG. 10 compares the change in the estimated value of the rotor temperature Trot with the change in the measured value (true value) of the rotor temperature Trot obtained in the experiment in the estimation system 10a of another example of the embodiment of FIGS. It is a diagram of In FIG. 10, at time _t1 , the rotation speed of the induction motor 50 changes from below the predetermined rotation speed to above the predetermined rotation speed. As a result, the switching unit 45 of the estimation system 10a of another example switches the rotor temperature estimating unit used for rotor temperature estimation from the low rotational speed rotor temperature estimating unit 43 to the high rotational speed rotor temperature estimating unit at time _t1 . 44, ie from Observer X to Observer Y. In such a configuration of another example, the rotor temperature Trot is estimated by using two models set at two rotation speeds and switching the models depending on the motor rotation speed. As a result, in the configuration of another example, as shown in FIG. 10, both the time 0- _t1 and the time exceeding _t1 make the estimated value of the rotor temperature Trot approximately equal to the measured value (true value). It was confirmed that the rotor temperature Trot could be estimated with high accuracy.

6 and 7, the estimation system has three or more rotor temperature estimation units corresponding to three or more motor rotation speed ranges, and the switching unit performs rotor temperature estimation according to the motor rotation speed. A configuration may be adopted in which the rotor temperature estimator used for is switched. In that case, the rotor temperature can be estimated with higher accuracy.

1 to 5 or the configurations of FIGS. 6 and 7, any element other than the rotor-side member 64 (FIG. 4) and the stator coil 55 among the elements of x in the formula (1) It is also possible to measure the temperature of the (eg stator core) and change the placement of 1 in c in equation (2) accordingly. In this case, the temperature of the element corresponding to y in equation (1) is also changed (eg, to the temperature of the stator core). Then, the measured temperature can be input to the rotor temperature estimating section 41 or the rotor temperature estimating sections 43 and 44 instead of the coil temperature Tcoil to obtain an estimated value of the rotor temperature Trot.

FIG. 11 is a block diagram showing a configuration of part of a control device in an estimation system 10b of another example of the embodiment. The estimation system 10b of FIG. 10 uses only one rotor temperature estimating unit 41a as in the configuration of FIG. 2 and FIG. The values of the matrix A and the gain F are changed according to the change in the detected value of the number N, and updated sequentially. As a result, the relational expression representing the thermal circuit model used in the rotor temperature estimator 41a includes a coefficient that varies with the motor rotation speed N. For this reason, a model is derived with the motor rotation speed N at each time, and the rotor temperature Trot is estimated with a model suitable at that time. Therefore, the rotor temperature estimator 41a can be realized as an observer corresponding to the motor characteristics each time, and the rotor temperature Trot can be accurately estimated. Other configurations and actions in this example are the same as those in FIGS.

Although the rotor temperature Trot can be estimated with high accuracy even with the configuration of FIG. 11, this configuration tends to increase the amount of control calculations. The configurations shown in FIGS. 6 and 7 are more preferable from the viewpoint of reducing the load on the arithmetic processing section of the control device 40 .

10, 10a, 10b rotor temperature estimation system (estimation system), 30 speed sensor, 31 coil temperature sensor, 32 outside temperature sensor, 40, 40a control device, 41, 41a rotor temperature estimation section, 42 motor loss calculator, 43 Low rotation speed side rotor temperature estimation unit 44 High rotation speed side rotor temperature estimation unit 45 Switching unit 50 Induction motor 51 First frame 52 Second frame 53 Stator 54 Stator core 55 Stator coil 60 Rotor 63 Rotating shaft, 64 Rotor-side member, 65 Load, 70, 71 Space, 72 Surrounding space, 73 Space, 75 Thermal resistance.

Claims (6)

For the induction motor, the motor rotation speed, the detected value of the stator coil temperature, the control command value or the detected value of the stator coil current value, the slip frequency, and the previous estimated value of the rotor temperature are input, and generated in the stator and rotor. a motor loss calculator for calculating a loss to
A calculated value of the loss generated in the stator and the rotor, a detected value of the stator coil temperature, and a detected value of the temperature of the outside air contacting the outside of the frame of the induction motor are input and set using the thermal energy balance. a rotor temperature estimator that obtains an estimated value of the rotor temperature from the model;
with
The model is a thermal circuit model and includes a plurality of thermally connected elements and thermal resistance between the plurality of elements. The thermal resistance of the air between is variable depending on the motor rotation speed,
Rotor temperature estimator for induction motors. The induction motor rotor temperature estimator of claim 1, wherein
The rotor temperature estimating unit obtains an estimated value of the rotor temperature using an observer designed using the model.
Rotor temperature estimator for induction motors. In the induction motor rotor temperature estimator according to claim 1 or claim 2 ,
The rotor temperature estimating unit is a plurality of rotor temperature estimating units prepared according to the motor rotation speed range of the induction motor,
A switching unit for switching the rotor temperature estimating unit used for estimating the rotor temperature according to the motor rotation speed,
Rotor temperature estimator for induction motors. A rotor temperature estimator for an induction motor according to claim 3 , wherein
In each of the models used in the plurality of rotor temperature estimating units, a value based on the thermal resistance of the air between the rotor and the stator is changed according to the reference motor rotation speed,
The rotor temperature estimator used for estimating the rotor temperature is switched according to the detected value of the motor rotation speed.
Rotor temperature estimator for induction motors. The induction motor rotor temperature estimator of claim 1, wherein
The relational expression representing the model used in the rotor temperature estimator includes a coefficient that varies with the motor speed.
Rotor temperature estimator for induction motors. A rotor temperature estimator for an induction motor according to any one of claims 1 to 5;
a rotation speed sensor that detects the rotation speed of the motor;
a coil temperature sensor that detects the stator coil temperature;
and an outside air temperature sensor that detects the temperature of the outside air,
detection signals from the rotation speed sensor, the coil temperature sensor, and the outside air temperature sensor are transmitted to the rotor temperature estimator;
Rotor temperature estimation system for induction motors.

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