DC Chopper

Chopper is a power electronic circuit that converts fixed direct current input voltage to variable DC output voltage. Chopper can increase (with a step up chopper) or decrease (with step down chopper) the level of the applied voltage. Similar to that of a transformer
in AC, the chopper can be used in DC to alter the voltage level easily with the advent of power electronics. Without the use of power electronics altering the voltage level in DC is difficult and uneconomical. It requires the use of motor-generator sets. 

AC link chopper

DC chopper

The DC to DC conversion with the use of power semiconductor devices can be done in two ways. One is the conversion of the input DC into AC with the help of an inverter then stepping up or stepping down the voltage level in a transformer and again converting in to DC with the help of a rectifier. This is called AC link chopper. The other is DC chopper which converts the DC input voltage directly to DC output in a single stage. An AC link chopper has two stage conversions, i.e. DC to AC and AC to DC. So an AC link copper is bulky, costly and inefficient whereas the DC chopper is converts in single stage is more efficient and compact.

Applications of choppers:

1. Electric transportation systems

2. Electric vehicles

3. Trolley cars etc.