The effect of long motor leads on PWM inverter fed AC motor drive systems

Advances in power electronic technology have improved the performance and output waveforms of PWM voltage source inverters and have made them the popular choice for many general purpose variable speed induction motor drives in energy saving applications. Switching frequencies of 10 to 20 kHz with 0.1 μs rise times are common with the current insulated gate bipolar transistor (IGBT) technology. In many industrial applications the PWM inverter and the motor must be at separate locations, thus requiring long motor leads. This paper examines the effect of long motor leads on high frequency PWM inverter fed AC motor drives. Cable transmission theory and cable capacitance analysis are presented and voltage reflections are investigated. A flexible computer model is developed and the analysis is confirmed by simulations and verified by experimental results from case studies