e-Learning in electrical engineering

Search | Navigation principles
Generalities Choppers Inverters Rectifiers Other converters

4. Example of function to be achieved: the chopper

Lecture's plan

Introduction

  1. Structure and command
  2. Example of function to be achieved: the rectifier
  3. Example of function to be achieved: the inverter
  4. Example of function to be achieved: the chopper
  5. Problems to be solved

 

 

We wish to supply a R-L load with an adjustable DC voltage starting from a fixed DC voltage source (figure 11) .

Figure 11

In order to obtain across the terminals of the load an adjustable voltage between zero up to the source's voltage, it is possible to

  • link the - terminal of the generator with the - terminal of the load

  • connect the other terminal of the load to the + and - terminals of the generator by the way of two semiconductor switches (figure 12).

    Figure 12

When K1 is closed, the voltage across the load's terminals is U.

When K2 is closed, the voltage across the load's terminals is zero.

By supplying to K1 and K2 a periodic command and by closing K1 during a fraction a of the period T, the voltage across the terminals of the load will be chopped, having the average value (the continuous component) aU. By modifying a from zero to 1, this component will change from zero to U (figure 13).

Figure 13

The inductance L of the receiver limits the fluctuations of the current, determined by the pulsatory voltage wave applied to the load.

The absorbed current is closer by a constant current when the inductance of the receiver is greater and/or the operation frequency f = 1/T, is greater.

 

Site coordinator: Damien Grenier | Thematic coordinator: Francis Labrique | Realization: Sophie Labrique | © e-lee.net
Last update: 2005, September, 30 | Translation: Sergiu Ivanov