# US 10,374,532 B2 · Apparatus, system and method of fault diagnosis for permanent magnet motor

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- Number: US 10,374,532 B2
- Document ID: US10374532B2
- Status: Granted
- Kind: B2
- Application number: 15/660,140
- Filed: 2017-07-26
- Published: 2018-10-11
- Granted: 2019-08-06
- Earliest claimed: 2017-04-06
- Assignees: Korea Electronics Technology Institute
- Applicants: Korea Electronics Technology Institute
- Inventors: Joonsung Park; Jinhong Kim; Byongjo Hyon; Junhyuk Choi
- Web page: https://patentgrep.com/patent/US10374532B2

## CPC

- H02P 6/12: Monitoring commutation; Providing indication of commutation failure
- H02P 6/085: {in a bridge configuration}
- H02P 29/0241: {the fault being an overvoltage}
- H02P 6/18: without separate position detecting elements
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

Disclosed are an apparatus, system and method for detecting, based on a mathematical model, a fault of a permanent magnet motor driven by a square wave. A fault diagnosis apparatus for the permanent magnet motor includes a current voltage measurement unit, a phase shift time calculation unit, and a control unit.

## Claims

### Claim 1

An apparatus for diagnosing a short-circuit in a motor that comprises a rotor of permanent magnet and stators of three-phases, the apparatus comprising:
a current voltage measurement unit connected to an inverter configured to drive the motor, the current voltage measurement unit configured to measure a current input and a voltage input to the motor received from the inverter; and
at least one controller configured to, for each phase of the motor;
compute a phase shift time of the motor indicating a time between a start and an end of a phase shift in the motor,
compute an inductance using the phase shift time, the current input and the voltage input,
compute an error value between the computed inductance and a predetermined reference inductance, and
when the error value is out of a predetermined range of normal operation, determine that a stator of the motor in a corresponding phase is short-circuited such that a short-circuited stator is detected while the motor is in operation,
wherein the system further comprises an output unit configured to generate a visual or audible alarm when a short-circuited stators detected.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the least one controller is configured to compute the inductance using Equation 1:
{
v
us
=
Ri
u
+
L
1
⁢
di
u
dt
+
e
u
v
vs
=
Ri
v
+
L
2
⁢
di
v
dt
+
e
v
v
ws
=
Ri
w
+
L
3
⁢
di
w
dt
+
e
w
[
Equation
⁢
⁢
1
]
where vus, vvs, and vws denote a u-phase voltage, a v-phase voltage, and a w-phase voltage of the motor, respectively, where iu, iv, and iw denote a u-phase current, a v-phase current, and a w-phase current of the motor, respectively, where L1, L2, and L3 denote a u-phase inductance, a v-phase inductance, and a w-phase inductance of the motor, respectively, where eu, ev, and ew denote a u-phase back electromotive force, a v-phase back electromotive force, and a w-phase back electromotive force of the motor, respectively, and where R denotes a resistance of the motor.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the at least one controller is configured to compute inductance of each phase by using Equation 2 derived from Equation 1:
L
1
=
(
t
2
-
t
1
)
⁢
(
DV
d
⁢
⁢
c
3
-
2
⁢
E
)
(
I
dc_e
-
I
dc_s
)
[
Equation
⁢
⁢
2
]
where Ln denotes the inductance of each phase, where n is from 1 to 3, where t2-t1 denotes the phase shift time, where t1 denotes a start time of the phase shift and t2 denotes an end time of the phase shift, where D denotes a PWM duty ratio, where Vdc denotes the input voltage, where E denotes an effective value of the back electromotive force, where Idc_s denotes an input current at the phase shift start, and where Idc_e denotes an input current at the phase shift end.

### Claim 4 (depends on 1)

The apparatus of claim 1, wherein the at least one controller is further configured to determine that a degree of short circuit using the error vale, and wherein the greater the error value is, the greater the degree of short circuit.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the at least one controller is further configured to determine a rating of short circuit and generate an alert corresponding to the rating of short circuit.

### Claim 6

A motor diagnosis system comprising:
a motor comprising a rotor of permanent magnet and stators of three-phases;
an inverter configured to drive the motor;
a current voltage measurement unit connected to the inverter and configured to measure a current input and a voltage input to the motor received from the inverter; and
at least one control unit configured to, for each phase of the motor:
compute a phase shift time of the motor indicating a time between a start and an end of a phase shift in the motor,
compute an inductance using the phase shift time, the current input and the voltage input,
compute an error value between the computed inductance and a predetermined reference inductance, and
when the error value is out of a predetermined range of normal operation, determine that a stator of the motor in a corresponding phase is short-circuited such that a short-circuited stator is detected while the motor is in operation.

### Claim 7

A method of diagnosing a short-circuit in a motor that has a rotor of permanent magnet and stators of three-phases, the method comprising:
measuring, using a current voltage measurement unit connected to an inverter for driving the motor, a current input and a voltage input to the motor by the inverter;
computing, by a controller, a phase shift time of the motor indicating a time between a start and an end of a phase shift in the motor;
computing, by the controller, an inductance using the phase shift time, the current input and the voltage input;
computing, by the controller, an error value between the computed inductance and a predetermined reference inductance; and
determining, by the controller, that a stator of the motor is short-circuited when the error value is out of a predetermined range of normal operation such that a short-circuited stator is detected while the motor is in operation.

### Claim 8 (depends on 7)

The method of claim 7, further comprising generating, by the controller, a visual or audible alarm when a short-circuited stator is detected.

### Claim 9 (depends on 6)

The system of claim 6, further comprising an output unit configured to generate a visual or audible alarm when a short-circuited stator is detected.