Design of line/motor side capacitors for PWM CSR-CSI drives to achieve optimal power factor in high power fan/pump applications

The input power factor of GTO PWM current source rectifiers using a delay angle control scheme is investigated. It is discovered that with an optimal design of line and motor side capacitors for CSR-CSI induction motor drives having fan/pump loads, the input power factor is close to unity (over 0.95 for 30% to 100% of rated load). The concept of near unity power factor operation is presented. The procedures for the capacitor design are discussed. A switching pattern suitable for the delay angle control with a low harmonic distortion is also introduced. The line current of the rectifier is near sinusoidal due to the use of the switching pattern and line side capacitor. Experimental results on a 5 HP drive are given to verify the theoretical analysis.