Method and protective circuit for monitoring the temperature of electric motors cooled by a coolant
First Claim
1. Method for monitoring the temperature of electric motors cooled by a coolant, wherein a sensor signal corresponding to the temperature of the motor (1) is generated and evaluated by way of at least one PTC thermistor (2), an output signal being generated when the sensor signal exceeds a predetermined threshold value, characterised in that the rate of change (dT/dt, dR/dt) of the sensor signal is also determined, whereby the threshold value at which the output signal is generated is changed as a function of the rate of change.
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Abstract
The invention relates to a method and a protective circuit for monitoring the temperature of electric motors cooled by a coolant, wherein a sensor signal corresponding to the temperature of the motor is generated and evaluated by way of at least one PTC thermistor, an output signal being generated when the sensor signal exceeds a predetermined threshold value. Furthermore, the rate of change of the sensor signal is also determined, whereby the threshold value at which the output signal is generated is altered as a function of the rate of change.
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6 Claims
- 1. Method for monitoring the temperature of electric motors cooled by a coolant, wherein a sensor signal corresponding to the temperature of the motor (1) is generated and evaluated by way of at least one PTC thermistor (2), an output signal being generated when the sensor signal exceeds a predetermined threshold value, characterised in that the rate of change (dT/dt, dR/dt) of the sensor signal is also determined, whereby the threshold value at which the output signal is generated is changed as a function of the rate of change.
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5. Protective circuit for monitoring the temperature of electric motors cooled by a coolant, with
a. at least one PTC thermistor (2) which generates a sensor signal corresponding the temperature of the motor (1), and b. an evaluation device (3) which generates an output signal (4) when the sensor signal exceeds a predetermined threshold value, characterised in that the evaluation device has means (3a) for determining the rate of change (dT/dt, dR/dt) of the sensor signal and means (3b) for adaptation of the threshold value as a function of the rate of change.
Specification