Choppers DC to DC converters | Power electronic lab report

Abstract

In this experiment for choppers power electronic lab report we will build a construction of the chopper circuit which it can control the DC voltage level ,both voltage and current outputs are to be examined.

Introduction

The principle of operation of this circuit is based on the fact that the average or DC voltage of a signal is directly proportional to the area enclosed by its waveform.

There are two type of these converters :

1. Step down (class A) choppers.
2. Step down (class B) choppers.


These converters uses the GTO as a switching device ,the only difference between the GTO will become off as soon as the gate pulse return to zero, this means that the gate pulse period is in fact the period of operation.

We will use in this power electronic lab report GTO to allow the voltage source to be seen by the load for only a part of the operation period, this means that we’ve changed the area under the waveform , thus the value of the average voltage at the load is change.

K is called the duty ratio of operation and its an important feature of the operation mode, its defined as TON/T, where TON is the time throw which GTO is conducting

Used equipment

- GTO and Diodes.
- R and Rl loads.
- AC Power Supply.
- Circuit Breakers.
- Connecting Wires.
- Digital Millimeter.
- Oscilloscope.
-Pulse generation circuit.
-DC voltage supply.


Chopper circuit:

The output wave form:

Conclusion

• The function of chopper circuit that it can control the DC voltage level .
• The average or DC voltage of a signal is directly proportional to the area enclosed by its waveform VDC = area/T.
• The use of an RL load clearly reduces the current ripple at the output for high value of time constant for the RL load.