Over temperature protection device for electric motors

Patent metadata

Field	Value
Publication number	US-9479107-B2
Application number	US-201114343492-A
Country	US
Kind code	B2
Filing date	Sep 8, 2011
Priority date	Sep 8, 2011
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

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.

First claim

The invention claimed is:

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 controls to stop operation of the inverter device when receiving an over temperature control signal; and
a protecting device configured to:
detect, information concerning a frequency of 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 of at least one phase flowing to the electronic motors;
generate an over temperature protection signal for protecting the electric motors from the over temperature when (i) the information concerning the frequency is lower than a specified frequency value, and (ii) a differential current between electric current detection values flowing to predetermined two electric motors among the electric motors is larger than a specified current value; and,
output the over temperature protection signal to the control device.

2. 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 the specified current value, determine that one of the two electric motors is likely to reach an over temperature and generate the over temperature protection signal.

3. 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 specified current value and the frequency is lower than the specified frequency value, determine that one of the two electric motors is likely to reach an over temperature and generate the over temperature protection signal.

4. 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 the specified frequency 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 the specified current 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.

5. 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 the specified current value and the frequency is lower than the specified frequency 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.

Assignees

• Kojiya Tomohiro
• Okada Yuruki
• Mitsubishi Electric Corp

Inventors

• Kojiya Tomohiro
• Okada Yuruki

Classifications

• B60L3/0061

  relating to electrical machines · CPC title

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• H02P2207/01

  Asynchronous machines · CPC title

• B60L2200/26

  Rail vehicles · CPC title

• H02P5/50

  by comparing electrical values representing the speeds · CPC title