• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1445-1450
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• 2007

Induction motors are the main driving force of electric vehicles and operated by pulse width modulation (PWM) inverters in speed control. Contrary to full-voltage operation of induction motors, inverter-fed induction motors (IFM) generates transient overvoltages up to 10 kV/us and transient overvoltages accelerate the deterioration of winding insulation. We investigated transient overvoltages produced by the operation of IFM and analyzed its peak value and dv/dt depending on power cable length and operation frequency. The experimental results showed that transient overvoltages measured at the motor terminal increased with the cable length between inverter and motor.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.650-654
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• 2007

Induction motors are widely used as a source of driving force in electric vehicles and pulse width modulation (PWM) inverters are applied to their operation. The issue is that insulation of inverter-fed induction motors (IFMs) are more stressed than in line-powered motors by transient voltages. This paper dealt with experimental results on transient voltage produced by the PWM operation of an induction motor. The peak and the dv/dt of transient voltage depending on the length of power feeding cable and operating frequency were investigated. In the experiment, transient voltages up to 3.3PU of the rated-inverter voltage were recorded for the cable length of 50m. As the cable length is increased, the peak voltage appeared at the motor terminals increases. This phenomenon can be explained by the reflection and the transmission of travelling wave. Consequently, special care for the cable length between the motor and the inverter should be taken in the use of IFM to ensure the full life of insulation system.