Torque estimating system for synchronous electric motor

Patent metadata

Field	Value
Publication number	US-10072993-B2
Application number	US-201414450797-A
Country	US
Kind code	B2
Filing date	Aug 4, 2014
Priority date	Jan 13, 2014
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A torque estimating system for a synchronous electric motor having a permanent magnet includes: a superimposing unit configured to superimpose a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor; a magnet temperature estimating unit configured to estimate a temperature of the permanent magnet from the superimposed voltage or current and a current or voltage obtained by the superimposing; and a torque estimating unit configured to estimate a torque of the synchronous electric motor from the estimated temperature of the permanent magnet.

First claim

What is claimed is:

1. A torque estimating system for a synchronous electric motor having a permanent magnet comprising:
a superimposing unit configured to superimpose a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor;
a magnet temperature estimating unit configured to estimate a temperature of the permanent magnet from the superimposed voltage or current and a current or voltage obtained by the superimposing;
a torque estimating unit configured to estimate a torque of the synchronous electric motor from the estimated temperature of the permanent magnet;
a calculator configured to calculate an impedance of the synchronous electric motor from the superimposed voltage or current and the current or voltage obtained by the superimposing; and
a temperature measuring unit configured to measure a temperature of a stator coil of the synchronous electric motor, wherein
when the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave on the synchronous electric motor, the calculator corrects a resistance value of the stator coil included in the impedance depending on the temperature of the stator coil measured by the temperature measuring unit and the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the impedance including the corrected resistance value of the stator coil.

2. The torque estimating system for the synchronous electric motor according to claim 1 , wherein
the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave only on the d-axis of the synchronous electric motor.

3. The torque estimating system for the synchronous electric motor according to claim 1 , wherein
the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave at predetermined intervals.

4. The torque estimating system for the synchronous electric motor according to claim 1 , wherein
the torque estimating unit estimates the torque on the basis of the estimated temperature of the permanent magnet and a pre-obtained relationship between the temperature of the permanent magnet and the torque of the synchronous electric motor.

5. The torque estimating system for the synchronous electric motor according to claim 1 , wherein
the calculator corrects the resistance value of the stator coil included in the impedance on the basis of the temperature of the stator coil measured by the temperature measuring unit and a pre-obtained relationship between the temperature of the stator coil and the resistance value of the stator coil, and the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the impedance including the corrected resistance value of the stator coil.

6. The torque estimating system for the synchronous electric motor according to claim 1 , wherein
the synchronous electric motor is driven by a current inverter,
the superimposing unit superimposes a current expressed by a formula (1) shown below on the synchronous electric motor,
the calculator uses a voltage which is obtained by superimposing the current expressed by the formula (1) shown below on the synchronous electric motor and which is expressed by a formula (2) shown below, to calculate the impedance expressed by a formula (3) shown below and obtained from the following formulae (1) and (2), wherein

[

i
dsc

*

i
qsc

*

]

=

[

I
c

⁢

⁢
sin
⁢

⁢

ω
c

⁢
t

0

]

(
1
)

where
i dsc * represents a d-axis harmonic current command value;
i qsc * represents a q-axis harmonic current command value;
I c represents an amplitude of d-axis harmonic current command value;
ω c represents an angular frequency of d-axis harmonic current command value; and
t represents a time,

[

v
dsc

v
qsc

]

=

[

(

R
d

+

j
⁢

⁢

Assignees

• Nissan Motor

Inventors

• Reigosa David Díaz
• Blanco Fernando Briz Del
• Yoshida Hideo
• Kato Takashi

Classifications

• H02K11/24

  Devices for sensing torque, or actuated thereby (H02K11/27 takes precedence) · CPC title

• G01L3/00 Primary

  Measuring torque, work, mechanical power, or mechanical efficiency, in general · CPC title

• H02K11/25

  Devices for sensing temperature, or actuated thereby · CPC title

• H02P21/20 Primary

  Estimation of torque · CPC title

• H02P29/67

  Controlling or determining the motor temperature by back electromotive force [back-EMF] evaluation · CPC title