JP2018093642A - Temperature estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature estimation device of a rotor of a dynamo-electric motor, which has a high general purpose.SOLUTION: In a temperature estimation device, an output torque Tthat is an actual torque of a dynamo-electric motor 1 that is operated in accordance with a driving signal (a three-phase current i, i, i) detected by six torques, is acquired, a torque calculation device 13 acquires: the driving signal (the three-phase current i, i, i); a position detection signal (a rotation angle θ) of the dynamo-electric motor 1, a d-axis inductance; q-axis inductance; and a calculation torque Tas a torque of the dynamo-electric motor 1 in a reference temperature calculated on the basis of a magnetic flux interlinked with a d-axis armature winding by a permanent magnet field in the reference temperature. Thus, a temperature of the dynamo-electric motor 1 is estimated on the basis of difference of the output torque Tand a calculation torque T.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature estimation device for a rotor of an electric motor.

  In an electric motor using a permanent magnet, when the temperature rises, the magnetic flux density of the permanent magnet decreases and the torque decreases. When the electric motor is in a high temperature state, the performance of the mechanical device that the electric motor moves may decrease due to a decrease in torque. Therefore, a device for estimating the temperature of the rotor of the electric motor may be provided.

  For example, Patent Document 1 discloses a temperature estimation device that estimates the magnet temperature of an electric motor based on the loss amount of the rotor and the temperature of the refrigerant.

JP 2014-93867 A

  However, the temperature estimation device of Patent Document 1 needs to prepare a loss amount map that is a map obtained by measuring torque and rotation speed in advance and connecting the same amount of loss amount with a solid line. Therefore, it is necessary to measure the amount of loss while changing the torque and the rotational speed for each electric motor, and it cannot be said that the versatility is high.

  The objective of this invention made | formed in view of this situation is providing the temperature estimation apparatus of the rotor of a motor with high versatility.

  In order to solve the above-described problem, the temperature estimation device according to the embodiment of the present invention includes an output torque that is detected by a torque meter and is an actual torque of an electric motor that operates according to a drive signal, and a torque calculator includes the drive signal. And at the reference temperature, calculated based on the position detection signal of the motor, the d-axis inductance, the q-axis inductance, and the magnetic flux interlinked with the d-axis armature winding by the permanent magnet field at the reference temperature. The calculated torque, which is the torque of the electric motor, is acquired, and the temperature of the rotor of the electric motor is estimated based on the difference between the output torque and the calculated torque.

を演算することによって前記電動機のロータの温度を推定する。 Preferably, the rotor temperature of the electric motor is τ, the output torque is T _out , the calculation torque is T _ref , the residual magnetic flux density temperature coefficient of a permanent magnet used in the electric motor is k, and the reference temperature is t _{As 0}

Is used to estimate the temperature of the rotor of the electric motor.

  The temperature estimation device according to the embodiment of the present invention can improve versatility.

It is a figure which shows the control system of the electric motor using the temperature estimation apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Motor control system)
FIG. 1 is a diagram illustrating a configuration example of a control system 20 for an electric motor 1 using a temperature estimation device 11 according to the present embodiment. The control system 20 is, for example, an automobile test system, but is not limited thereto, and can be applied as a control system for all types of electric motors 1 on which a torque meter is mounted.

  The control system 20 includes an electric motor 1, a power converter 2, a load 5, a torque meter 6, a position sensor 7, a current detector 8, a temperature estimation device 11, a current controller 12, and a torque calculator. 13.

  As shown in FIG. 1, the electric motor 1 is powered and driven by using a power converter 2 that performs DC / AC conversion. In this embodiment, the power converter 2 is a three-phase PWM inverter. A known configuration can be used for the three-phase PWM inverter. Further, the power converter 2 is used by being connected to a system, for example.

A load 5 is connected to the output side of the electric motor 1. A torque meter 6 for measuring the actual torque of the electric motor 1 is provided between the electric motor 1 and the load 5. The torque meter 6 is connected to the electric motor 1 and outputs the detected output torque T _out of the electric motor 1 to the temperature estimation device 11. The torque meter 6 may be, for example, a flange type, but is not limited to this.

In addition, a position sensor 7 is attached to the electric motor 1. The position sensor 7 detects the rotational position (rotational angle θ _m ) of the rotor with respect to the reference of the stator. Examples of the position sensor 7 include an encoder and a resolver, but are not limited thereto.

A current detector 8 is connected between the electric motor 1 and the power converter 2. The current detector 8 detects three-phase currents i _u , i _v and i _w flowing from the electric motor 1 to the power converter 2.

The current controller 12 _acquires current commands (d-axis current command i _dref and q-axis current command i _qref ) and _outputs three-phase voltage commands v _u , v _v , and v _w . In addition, the current controller 12 acquires the three-phase currents i _u , i _v , i _w detected by the current detector 8 and the rotation angle θ _m detected by the position sensor 7. Here, the three-phase currents i _u , i _v , and i _w are examples of drive signals for the electric motor 1. Further, the rotation angle θ _m is an example of a position detection signal of the electric motor 1.

The current controller 12 generates the three-phase voltage commands v _u , v _v , and v _w so that the three-phase currents i _u , i _v , and i _w converted into the two-phase currents coincide with the current command. The current controller 12 performs PI control using, for example, a current command and currents based on the three-phase currents i _u , i _v , and i _w (d-axis current i _d and q-axis current i _q ). Here, the d-axis current i _d and the q-axis current i _q are, for example, the currents i _α and i _β in the αβ-axis system obtained by three-phase to two-phase conversion of the three-phase currents i _u , i _v and i _w. Further, it can be obtained by converting rotational coordinates using the rotational angle θ _m .

The torque calculator 13 acquires the d-axis inductance L _d , the q-axis inductance L _q, and the flux linkage φ ₂₀ . Moreover, the torque calculator 13 acquires the three-phase currents i _u , i _v , i _w and the rotation angle θ _m . The torque calculator 13 outputs the calculated torque T _ref20 to the temperature estimation device 11. The d-axis inductance L _d , the q-axis inductance L _q , and the linkage flux φ ₂₀ are determined by the characteristics of the magnet used in the electric motor 1. The torque calculator 13 may acquire the d-axis inductance L _d , the q-axis inductance L _q , and the flux linkage φ ₂₀ from a storage unit (for example, a semiconductor memory or a magnetic memory) that stores the characteristics of the electric motor 1. The calculated torque T _ref20 is obtained by the following output torque equation (1).

Here, p is the number of pole pairs of the permanent magnet used in the electric motor 1. The interlinkage magnetic flux φ ₂₀ is a magnetic flux interlinked with the d-axis armature winding by the permanent magnet field at the reference temperature (20 ° C. in the present embodiment). The d-axis current i _d and the q-axis current i _q are obtained by calculation using the three-phase currents i _u , i _v , i _w and the rotation angle θ _m as described in the explanation of the current controller 12. Linkage flux phi ₂₀ of the coefficients used in the formula (1) may depend on the temperature. In other words, flux linkage phi at a temperature not 20 ° C. is different from the flux linkage phi _20. On the other hand, the d-axis inductance L _d and the q-axis inductance L _q do not change even when the temperature changes.

As another example, the torque calculator 13 may calculate the calculated torque T _ref20 using a torque map. The control system 20 may use a torque map that tabulates the optimum d-axis current _id and q-axis current _iq for each rotation speed and torque of the electric motor 1. The torque map is created based on, for example, simulation results. The torque calculator 13 is not the above formula (1), but the d-axis current i _d and the q-axis current i _q obtained from the three-phase currents i _u , i _v , i _w and the rotation angle θ _m , the torque map, The calculation torque T _ref20 may be calculated using.

The temperature estimation device 11 acquires the output torque T _out and the calculated torque T _ref20 . Moreover, the temperature estimation apparatus 11 acquires the residual magnetic flux density temperature coefficient k mentioned later. The temperature estimation device 11 obtains (estimates) the temperature τ of the rotor of the electric motor 1 by calculation and outputs it as a signal W. Here, the calculated torque T _ref20 is a value of the torque of the electric motor 1 at the reference temperature (20 ° C. in the present embodiment). When the temperature of the electric motor 1 rises above 20 ° C., the linkage flux φ changes from the linkage flux φ ₂₀ used in the equation (1), so that the output torque T _out becomes smaller than the calculated torque T _ref20 . The temperature estimation device 11 can calculate the temperature τ of the rotor of the electric motor 1 based on the difference between the output torque T _out detected by the torque meter 6 and the calculated torque T _ref20 . Here, the temperature estimation device 11 outputs, as the signal W, an alert signal indicating that the temperature τ of the rotor of the electric motor 1 has exceeded a predetermined temperature (for example, 150 ° C.) instead of the temperature τ obtained by calculation. Also good. For example, a main controller (not shown) that controls the overall operation of the control system 20 may acquire the signal W from the temperature estimation device 11. When the main controller determines that the temperature τ of the rotor of the electric motor 1 has exceeded a predetermined temperature, the main controller adjusts the current command so as to suppress the output torque T _out of the electric motor 1 or sets the electric motor 1 for protection. You may stop it.

(Calculation of temperature)
The temperature estimation device 11 can calculate the temperature τ of the rotor of the electric motor 1 using an expression described below. The permanent magnet used in the electric motor 1 has a unique residual magnetic flux density temperature coefficient k [% / K] as one of temperature characteristics. In this embodiment, since the reference temperature is 20 ° C., the following equation (2) is set between the residual magnetic flux density temperature coefficient k, the rotor temperature τ of the electric motor 1, the output torque T _out, and the calculated torque T _ref20. ).

The left side of Equation (2) represents the rate of change [%] in magnetic flux obtained by multiplying the increase (τ−20) of the rotor temperature τ from 20 ° C. by the residual magnetic flux density temperature coefficient k. On the other hand, the rate of change [%] of the magnetic flux can be obtained as the rate of change of the output torque T _{out based on} the 20 ° C. torque (calculated torque T _ref20 ) as shown on the right side of the equation (2). Therefore, Expression (2) is established. Moreover, the following formula (3) is obtained by modifying the formula (2).

The temperature estimation device 11 outputs the temperature τ (or a signal based on the temperature τ) of the rotor of the electric motor 1 obtained by Expression (3) as a signal W. For example, it is assumed that a neodymium magnet is used for the electric motor 1. As an example, the residual magnetic flux density temperature coefficient k of the neodymium magnet is −0.1 [% / K]. Further, it is assumed that the temperature estimation device 11 has acquired the calculation torque T _ref20 = 80 [Nm] and the output torque T _out = 68 [Nm]. At this time, the temperature estimation apparatus 11 estimates that the temperature τ of the rotor of the electric motor 1 is 170 ° C. by calculating using the equation (3). And the temperature estimation apparatus 11 outputs the signal W which shows that temperature (tau) is 170 degreeC. As another example, the temperature estimation device 11 outputs a signal W indicating that the temperature τ has exceeded a predetermined temperature (for example, 150 ° C.). At this time, the main controller that has acquired the signal W may adjust the current command so as to suppress the output torque T _out of the electric motor 1.

As described above, the temperature estimation device 11 according to the present embodiment is the actual torque of the electric motor 1 that operates according to the drive signals (three-phase currents i _u , i _v , i _w ) detected by the torque meter 6. The output torque T _out is acquired. Further, the temperature estimation device 11 is based on a reference calculated by the torque calculator 13 based on at least the drive signals (three-phase currents i _u , i _v , i _w ) and the position detection signal (rotation angle θ _m ) of the electric motor 1. A calculated torque T _ref20 that is the torque of the electric motor 1 at the temperature is acquired. Temperature estimation device 11, based on the difference between the output torque _{T out} an operational torque _{T Ref20,} estimates the temperature of the motor 1. The above equation (3) is used to estimate this temperature.

  The temperature estimation device 11 according to the present embodiment does not need to measure the torque and the rotational speed in advance in order to create a loss amount map, for example. Therefore, the present invention can be applied to the control system 20 of the electric motor 1 for various uses without special preparation (creation of a loss amount map or the like). That is, the temperature estimation device 11 according to the present embodiment is highly versatile.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various changes and modifications based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

In the above embodiment, the reference temperature is 20 ° C., but other temperatures may be used as the reference temperature. At this time, assuming that the calculation torque at the reference temperature is T _ref and the reference temperature is t ₀ , the temperature estimation device 11 can calculate (estimate) the temperature τ of the rotor of the electric motor 1 by the following equation (4).

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Power converter 5 Load 6 Torque meter 7 Position sensor 8 Current detector 11 Temperature estimation apparatus 12 Current controller 13 Torque calculator 20 Control system

Claims (2)

An output torque that is detected by a torque meter and is an actual torque of an electric motor that operates according to a drive signal;
A torque calculator is based on the drive signal, the position detection signal of the motor, the d-axis inductance, the q-axis inductance, and the magnetic flux interlinked with the d-axis armature winding by the permanent magnet field at the reference temperature. And the calculated torque, which is the torque of the electric motor at the reference temperature,
A temperature estimation device that estimates a temperature of a rotor of the electric motor based on a difference between the output torque and a calculation torque. The temperature of the rotor of the motor is τ, the output torque is T _out , the calculation torque is T _ref , the residual magnetic flux density temperature coefficient of the permanent magnet used in the motor is k, and the reference temperature is t ₀ ,

The temperature estimation device according to claim 1, wherein the temperature of the rotor of the electric motor is estimated by calculating.

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