A Unique Transistorized High Power PWM Inverter

The principle of Pulse Width Modulation (PWM) has been well known for decades. A patent was actually issued in 1944, but it was not until the early sixties that the principle began to be widely applied to power conversion. Today the PWM principle is applied extensively in the power conversion field. However, the full advantage of this principle, as applied to inverters, can only be realized by appropriate design of the power bridge units, control and regulation loops etc. This paper provides an outline to the design of a unique high power PWM inverter series, which uses large hiqh current bipolar power transistors in its power bridge to achieve power ratings from a few KVA, to over 200kVA. The paper will also cover the control principles applied, and some of the techniques employed in a practical realization of the workinq unit. The uniqueness of the subject PWM inverter will be furter illustrated by comparisons with other commonly employed inverter technologies. Finally, the practical realization of such characteristics as efficiency, dynamic response, disortion, power factor and the effect of load induced harmonics (high crest factor currents), will be presented as related to the subject design and there importance as related to todays typical loads.