# US 10,768,236 B2 · Method for detecting a rotor bar fault

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- Number: US 10,768,236 B2
- Document ID: US10768236B2
- Status: Granted
- Kind: B2
- Application number: 16/496,863
- Filed: 2018-03-06
- Published: 2020-04-09
- Granted: 2020-09-08
- Earliest claimed: 2017-03-30
- Assignees: ABB Schweiz AG
- Applicants: ABB Schweiz AG
- Inventors: Pedro Rodriguez; Subrat Sahoo
- Web page: https://patentgrep.com/patent/US10768236B2

## CPC

- G01R 31/343: {in operation}
- H02K 3/20: for auxiliary purposes, e.g. damping or commutating
- H02K 11/25: Devices for sensing temperature, or actuated thereby
- H02K 19/14: having additional short-circuited windings for starting as asynchronous motors
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A rotor bar fault in a rotor of an electrical machine having a plurality of rotor bars and an end ring configured to short circuit the rotor bars. The method includes the steps of measuring a first temperature at a first end ring location, and measuring a second temperature at a second end ring location, the second end ring location being different from the first end ring location. As broken rotor bars cause a non-uniform temperature distribution in the end ring, the detection of rotor bar faults can be based on monitored temperatures at different end ring locations.

## Claims

### Claim 1

A method for detecting a rotor bar fault in a rotor of an electrical machine having a plurality of rotor bars and an end ring configured to short circuit the rotor bars, the method comprising the steps of:
measuring a first temperature at a first end ring location, and measuring a second temperature at a second end ring location, the second end ring location being different from the first end ring location;
calculating a temperature difference between the first temperature and the second temperature;
calculating a temperature difference change between the temperature difference at a first time and the temperature difference at a second time; and
using the temperature difference, the temperature difference change, or both to determine that a rotor bar fault is present.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the method further includes the step of comparing the temperature difference change with a predetermined second threshold value.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the method further includes at least one of the following steps:
determining, on the basis that the temperature difference change is equal to or higher than the predetermined second threshold value, that a rotor bar fault is present, and
determining, on the basis that the temperature difference change is lower than the predetermined second threshold value, that a rotor bar fault is not present.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the method further includes the step of comparing the temperature difference with a predetermined first threshold value.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the method further includes at least one of the following steps:
determining, on the basis that the temperature difference is equal to or higher than the predetermined first threshold value, that a rotor bar fault is present, and
determining, on the basis that the temperature difference is lower than the predetermined first threshold value, that a rotor bar fault is not present.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the method further includes the step of measuring the temperature at more than two different end ring locations, such as at three, at four, at six, at eight, at ten, or at twelve different end ring locations.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the rotor has a plurality of rotor poles, and the method further includes the step of measuring another temperature at a number of different end ring locations, the number of different end ring locations being equal with or a multiple of the number of rotor poles.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the method is carried out during a normal operation of the electrical machine.