Type C chopper

As we know that a chopper is a static device that convert fixed dc input voltage to a variable dc output voltage directly. This characteristic of their operation in any four quadrants form the basis of their classification as class A, class B, class C, Class D, class E etc.

This type of chopper is also called as two quadrant called type A chopper. This type of chopper is obtained by connecting type A and type B choppers in parallel as shown in figure given below.
  • The output voltage Vis always positive because of the presence of a freewheeling diode called FD across the load. 
  • When chopper CH2  is on, or freewheeling diode conducts, output voltage V0 = 0 and in case chopper CH1 is on or diode D2 conduct, output voltage is equal to the voltage V=  Vs
  • The load current called Ican, however, reverse its direction. 
  • Current flows in the arrow direction marked in the figure.
  • The load current is positive when CH1 is on or FD operate together as type A chopper in the first quadrant. 
  • Likewise, CH2 and D2 operate together as type B chopper in the second quadrant.
  • Average load voltage is always positive but the average load current may be positive or negative as explain above.
  • Therefore, power flow may be from source to load or from load to source.
  • So in Chopper CH1 and chopper CH2 should not be on simultaneously as this would lead to a direct short circuit on the supply lines.
  • This type of chopper configuration is used for motoring and regenerative braking of dc motors
  • This type of operating region of this type of chopper is shown in figure second by the hatched area in the first and second quadrants.