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Voltage analysis of PWM inverter fed induction motors

Adjustable Speed Drive (ASD) systems are widely used in industry to
effectively improve process efficiency and control. Typically, an ASD system consists
of a motor with its speed controlled by a power electronics converter via varying the
amplitude and frequency of the input voltage. However, several abnormal insulation
failures of random wound motors in ASD applications have been reported. These
failures were related to voltage transients caused by inverters employing fast insulated
Gate Bipolar Transistors (IGBTs) combined with long cables that connect motors to
This thesis further analyzes the distribution of voltage waveforms generated by a
pulse-width modulated (PWM) inverter at the motor terminals and windings.
Experimental work was performed at the Motor Systems and Resource Facility (MSRF)
at Oregon State University on a specially made 5hp induction motor with taps from the
first and second coil and from the first four and last two turns in every phase. Tests were
performed with long and short cables and results are compared. A simple simulation
model was created in PSpice and used to predict maximum voltage transients across
coils and turns. The validation of the model is demonstrated by its capability to predict
most of the experimental results. / Graduation date: 2000
Date21 May 1999
CreatorsAl-Ghubari, Fahad H.
ContributorsWallace, Alan K., Von Jouanne, Annette R.
Source SetsOregon State University
Detected LanguageEnglish

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