Abstract

Conventional AC power controllers use antiparallel Thyristors or Triacs. Simple circuits such as this are commonly used in heating control and dimmer switches. The delay of the input line voltage causes a shift in the line current?s fundamental component (Phase Controlled Modulator).This shift and the non-sinusoidal line current resulting from this control and produces a negative impact on the power supply system.

The company <Brutsch Elektronik> builds devices for welding plastic tubes. The temperature for the heating wire empolyed in the welding process is controlled by an AC power controller. The increasingly restrictive EMC- regulations, however, force the company to develop a new solution based on IGBTs. Our task consisted in drafting and testing a new concept for an improved AC power controller, with special emphasis on the repercussions of the power controller on the line. The rms value of the output voltage will be set through the switching on and off of the IGBT, based on pulse width signals. When applying inductive loads, it is crucial, due to this particular setup of switches, to include a free wheeling circuit. The main concept and the bidirectional switches FIO50-12BD to be used, which consists of an IGBT and a fast diode bridge, were set as a starting point for our research by our lecturer.

In our dissertation, we simulated such an AC power controller and compared it to a conventional one. In addition, we built the complete circuit with a PWM-Generator and drivers for the IGBTs and evaluated the results of our measurements.

However, because of the negative impact of the new AC power controller on the power supply system and the considerable amount of power electronics that are needed, this concept is not yet developed enough to become a replacement for the conventional AC power controller.