Design Consideration of Power Electronic Equipment

Power electronic equipment design can be divided into four main areas:

1. Design of power circuits
2. Protection of power devices
3. Determination of control strategy
4. Design of logic and gating circuits

Peripheral Effects

Power converters operate on the basis of switching power semiconductor devices on and off. These switching actions of converters introduce current and voltage harmonics into:

1. The supply system
2. The output of converters

The problems caused by these harmonics are:

1. Distortion of the output voltage
2. Distortion of the supply voltage
3. Interference with communication and signaling circuits
4. Reduction of input power factor

The following methods can be used to solve or reduce harmonic problems caused by power converters:

1. Use of input and output filters on power converters
2. Choice of control strategy used, 3. Grounded shielding.

The role of transformers in power electronics

1. It provides for isolation of high and low voltage circuits, such as between control circuits, power circuits and sensor circuits.
2. It matches the output voltage of a converter to the requirements of a load, by taking advantage of the turns-ratio. Often the power device voltage rating and the fixed ac supply voltage forces a transistor to be used.
3. It allows operation of a converter at a suitable duty cycle (i.e., not too small) when the converter is required to develop a low output voltage.
4. Use of a high frequency transformer often reduces the overall size of the converter and allows operation at a convenient duty cycle.

Transformer relationships:

previous Classification of Converters