Transient effects in application of PWM inverters to inductionmotors

Standard squirrel cage induction (SCI) motors are subjected to nonsinusoidal wave-shapes when supplied from adjustable-frequency inverters. In addition to causing increased heating, these wave patterns can be destructive to the insulation. In particular, pulse-width-modulated (PWM) inverter output amplitudes and risetimes are investigated. Motor insulation capabilities are discussed. Voltage reflections are simulated for various cable lengths and risetimes and are presented graphically. Simulations confirm potential problems with long cables and short risetimes. Application precautions are also suggested