Analysis of PWM Frequency Control to Improve the Lifetime of PWM Inverter

Studies show that the power cycling mean time to failure (MTTF) of the insulated-gate bipolar transistor (IGBT) bond wire in an adjustable speed drive may be very short under some very common conditions. This paper proposes a switching frequency reduction method based on the junction temperature variation (Delta T-j) of an inverter IGBT. It has the following advantages. First, it reduces the pulsewidth-modulation frequency under low-speed higher torque condition. Second, the inverter is started more smoothly and safely under higher command switching frequency and high-torque condition. Third, the overall MTTF of the inverter IGBT can be improved. The theory analysis, simulation, and experimental result are provided to show these advantages.