# US 2014/0197769 A1 · Over temperature protection device for electric motors

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- Number: US 2014/0197769 A1
- Document ID: US20140197769A1
- Status: Published application
- Kind: A1
- Application number: 14/343,492
- Filed: 2011-09-08
- Published: 2014-07-17
- Earliest claimed: 2011-09-08
- Assignees: Mitsubishi Electric Corporation
- Inventors: Tomohiro Kojiya; Yuruki Okada
- Web page: https://patentgrep.com/patent/US20140197769A1

## CPC

- H02P 29/64: Controlling or determining the temperature of the winding
- B60L 3/0061: {relating to electrical machines}
- H02P 5/50: by comparing electrical values representing the speeds
- H02P 27/047: {V/F converter, wherein the voltage is controlled proportionally with the frequency}
- H02P 29/027: {the fault being an over-current}
- H02P 29/032: Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
- H02P 29/60: Controlling or determining the temperature of the motor or of the drive (H02P29/02 takes precedence)
- B60L 2200/26: Rail vehicles
- B60L 2220/42: with use of more than one motor
- H02P 2207/01: Asynchronous machines
- Y02T 10/64: Electric machine technologies in electromobility
- Y02T 10/72: Electric energy management in electromobility
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An over temperature protection device for electric motors applicable to a railway vehicle driving system that operates a plurality of electric motors in parallel using one or a plurality of inverter devices includes a control device configured to control the operation of an inverter device and a protecting device configured to detect, on the basis of a frequency fs including frequency information at the time when the inverter device is applying control for fixing a ratio of a voltage and a frequency to electric motors and electric currents of at least one phase flowing to the electronic motors, an over temperature that could occur in the electric motors, to generate an over temperature protection signal Tf for protecting the electric motors from the over temperature, and to output the over temperature protection signal Tf to the control device.

## Claims

### Claim 1

An over temperature protection device for electric motors applicable to a railway vehicle driving system that operates a plurality of electric motors in parallel using one or a plurality of inverter devices, the over temperature protection device comprising:
a control device configured to control an operation of the inverter device; and
a protecting device configured to detect, based on information concerning the frequency at the time when the inverter device is applying control for fixing the ratio of a voltage and a frequency to the electric motors and an electric current a current detection value of at least one phase flowing to the electronic motors and output, on the basis of a result of determination as to whether the information concerning the frequency is lower than a specified value and a result of determination as to whether a differential current between electric current detection values flowing to predetermined two electric motors among the electric motors is larger than a specified value, to generate an over temperature protection signal for protecting the electric motors from the over temperature, and to output the over temperature protection signal to the control device.

### Claim 2 (depends on 1)

The over temperature protection device for electric motors according to claim 1, wherein
when the inverter device controls two electric motors,
the protecting device includes:
a differential-current calculating unit configured to, when the frequency is smaller than a specified value, calculate the differential current between current detection values flowing to the two electric motors; and
an over-temperature-protection-signal generating unit configured to, when the differential current is larger than a specified value, determine that one of the two electric motors is likely to reach an over temperature and generate the over temperature protection signal.

### Claim 3 (depends on 1)

The over temperature protection device for electric motors according to claim 1, wherein
when the inverter device controls two electric motors,
the protecting device includes:
a differential-current calculating unit configured to calculate a differential current between current detection values flowing to the two electric motors; and
an over-temperature-protection-signal generating unit configured to, when the differential current is larger than a specified value and the frequency is lower than a specified value, determine that one of the two electric motors is likely to reach an over temperature and generate the over temperature protection signal.

### Claim 4 (depends on 1)

The over temperature protection device for electric motors according to claim 1, wherein
when the inverter device controls N (N is an integer equal to or larger than 3) electric motors,
the protecting device includes:
a differential-current calculating unit configured to, when the frequency is lower than a specified value, calculate N−1 differential currents including at least one of current detection values flowing to the N electric motors; and
an over-temperature-protection-signal generating unit configured to, when at least one differential current among the N−1 differential currents is larger than a specified value, determine that an over temperature could occur in an electric motor group configured from the N electric motors and generate the over temperature protection signal.

### Claim 5 (depends on 1)

The over temperature protection device for electric motors according to claim 1, wherein
when the inverter device controls N (N is an integer equal to or larger than 3) electric motors,
the protecting device includes:
a differential-current calculating unit configured to calculate N−1 differential currents including at least one of current detection values flowing to the N electric motors; and
an over-temperature-protection-signal generating unit configured to, when at least one differential current among the N−1 differential currents is larger than a specified value and the frequency is lower than a specified value, determine that an over temperature could occur in an electric motor group configured from the N electric motors and generate the over temperature protection signal.