Abstract: This paper discusses the basic principle which the inverted firing angle of thyristor inverter has the influence on power factor of a cascade connected device. On the basis of this principle, if it adopts a PWM type of cascade connected device, the power factor is improved to a certain extent. The tested results fully prove that the thcoritical analysis is correct.
Because the construction and control of this PWM type of cascade connected device are comparatively simple and the economic benefit by using of this device is got.