# US 12,224,692 B2 · Electric motor fault detection

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- Number: US 12,224,692 B2
- Document ID: US12224692B2
- Status: Granted
- Kind: B2
- Application number: 18/059,337
- Filed: 2022-11-28
- Published: 2023-06-01
- Granted: 2025-02-11
- Earliest claimed: 2021-11-30
- Assignees: NXP USA, Inc.
- Applicants: NXP USA, Inc.
- Inventors: Matej Pacha
- Web page: https://patentgrep.com/patent/US12224692B2

## CPC

- H02P 21/13: Observer control, e.g. using Luenberger observers or Kalman filters
- H02P 29/028: the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault
- H02P 6/182: using back-emf in windings
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

An electric motor controller having fault detection comprises: a driver circuit configured to drive an electric motor in response to a received speed demand signal; a measurement circuit configured to measure current through windings of the electric motor, the measurement circuit comprising a back emf, BEMF, observer configured to determine an estimated BEMF value, a BEMF error threshold and an estimated rotor angular speed value from the measured currents; a detector circuit configured to receive the rotor speed demand signal, the estimated BEMF value, the BEMF error threshold, the estimated rotor angular speed value and a measured rotor speed from a rotor speed sensor on the electric motor and to detect a fault in the electric motor controller if the estimated BEMF value lies outside the BEMF error threshold and the measured rotor speed is within a defined rotor speed error threshold.

## Claims

### Claim 1

An electric motor controller comprising:
a driver circuit configured to drive an electric motor in response to a received speed demand signal;
a measurement circuit configured to measure current through windings of the electric motor, the measurement circuit comprising a back emf (BEMF) observer configured to determine an estimated BEMF value, a BEMF error threshold and an estimated rotor angular speed value from the measured currents;
a detector circuit configured to receive the rotor speed demand signal, the estimated BEMF value, the BEMF error threshold, the estimated rotor angular speed value and a measured rotor speed from a rotor speed sensor on the electric motor and to detect a fault in the electric motor controller if the estimated BEMF value lies outside the BEMF error threshold and the measured rotor speed is within a defined rotor speed error threshold.

### Claim 2 (depends on 1)

The electric motor controller of claim 1, wherein the detector circuit is configured to cause the driver circuit to disable the motor if a fault is detected.

### Claim 3 (depends on 1)

The electric motor controller of claim 1, wherein the detector circuit is configured to output a fault indication if a fault is detected.

### Claim 4 (depends on 1)

The electric motor controller of claim 1, wherein the rotor speed error threshold is defined from the rotor speed demand signal.

### Claim 5 (depends on 1)

The electric motor controller of claim 1, wherein the rotor speed error threshold is a range within around +/−10% of the rotor speed demand signal.

### Claim 6 (depends on 1)

The electric motor controller of claim 1, wherein the rotor speed error threshold is a range within around +/−5% of the rotor speed demand signal.

### Claim 7

An electric motor system comprising:
an electric motor having a stator, a rotor and a rotor speed sensor connected to the rotor; and
an electric motor controller comprising:
a driver circuit configured to drive an electric motor in response to a received speed demand signal;
a measurement circuit configured to measure current through windings of the electric motor, the measurement circuit comprising a back emf (BEMF) observer configured to determine an estimated BEMF value, a BEMF error threshold and an estimated rotor angular speed value from the measured currents;
a detector circuit configured to receive the rotor speed demand signal, the estimated BEMF value, the BEMF error threshold, the estimated rotor angular speed value and a measured rotor speed from a rotor speed sensor on the electric motor and to detect a fault in the electric motor controller if the estimated BEMF value lies outside the BEMF error threshold and the measured rotor speed is within a defined rotor speed error threshold.

### Claim 8 (depends on 7)

The electric motor system of claim 7, wherein the electric motor is a permanent magnet synchronous motor.

### Claim 9

A method of detecting a fault in an electric motor controller, the electric motor controller comprising:
a driver circuit configured to drive an electric motor in response to a received speed demand signal;
a measurement circuit configured to measure current through windings of the electric motor, the measurement circuit comprising a back emf (BEMF) observer configured to determine an estimated BEMF value, a BEMF error threshold and an estimated rotor angular speed value from the measured currents; and
a detector circuit configured to receive the rotor speed demand signal, the estimated BEMF value, the BEMF error threshold, the estimated rotor angular speed value and a measured rotor speed from a rotor speed sensor on the electric motor,
the method comprising the detector circuit detecting a fault in the electric motor controller if the estimated BEMF value lies outside the BEMF error threshold and the measured rotor speed is within a defined rotor speed error threshold.

### Claim 10 (depends on 9)

The method of claim 9, wherein the detector circuit causes the driver circuit to disable the motor if a fault is detected.

### Claim 11 (depends on 9)

The method of claim 9, wherein the detector circuit outputs a fault indication if a fault is detected.

### Claim 12 (depends on 9)

The method of claim 9, wherein the rotor speed error threshold is defined from the rotor speed demand signal.

### Claim 13 (depends on 9)

The method of claim 9, wherein the rotor speed error threshold is a range within around +/−10% of the rotor speed demand signal.

### Claim 14 (depends on 9)

The method of claim 9, wherein the rotor speed error threshold is a range within around +/−5% of the rotor speed demand signal.