20 September 2018

Type E chopper

As we that a chopper is one type of electronic circuit used to refer numerous types of electronic switching devices and used in power control and signals applications. 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. Now let us check it out the information about type E chopper to know more details about the chopper.

The power diagram for a four-quadrant chopper is shown in the figure. 
  • It consists of four semiconductor switches CH1 to CH4 and also four diode D1 to D4 in anti-parallel.
  • The numbering of chopper CH1,...CH4  corresponds to their respective quadrant operation.
  • For example for first quadrant operation, only chopper CH1 is operated for second quadrant operation, only CH2 is operated and so on. 
  • Working of this chopper in the four quadrants is explained as under four quadrants is given below.
First quadrant :
  • For 1st quadrant operation of the figure shown chopper CH4 is kept ON, CH3 is kept off and chopper CH1 is operated.
  • With chopper CH1, CH4 on load voltage V= Vs and load current I0 begins to flow. 
  • Here both voltage, as well as current V0 and I0, are positive giving first quadrant operation.
  • When CH1 is turn off positive current freewheels through chopper CH4, D2.
  • In this manner, both voltage and current V0, I0 can be controlled in the first quadrant.
Second quadrant :
  • Here CH2 is operated and CH1, CH3, and CH4 kept off.
  • With CH2 on, reverse current flows through L, CH2, D4, and E inductance L stores energy during the time CH2 is on.
  • When CH2 is turn off current is fed back to the source through diodes D1, D4. 
  • Note that here the voltage (E+L di/dt) is more than the source voltage of Vs.
  • As load voltage V0 is positive and I0 is negative, it is the second quadrant operation of the chopper, Also power is fed back from load to source.
  • So this quadrant, configuration operates as a step-up type of chopper.
Third quadrant :
  • For third quadrant operation, chopper CH1 is kept off, chopper CH2 is kept on and CH3  is operated.
  • Polarity of load emf E must be reversed for this quadrant working.
  • When chopper CH3 is on, the load gets connected to source Vs so that both V0, I0 are negative leading to third quadrant operation.
  • When chopper CH3 is turn off, negative current freewheels through CH2, CH4. 
  • In this manner V0 and I0 can be controlled in the third quadrant.
  • Here chopper operates as a step-down, the chopper operates as a step down a chopper.
Fourth quadrant :
  • And last here chopper CH4 is operated and also some other devices are kept off. Load emf E has its polarity and its as shown in figure for its operation in the fourth quadrant.
  • With chopper CH4 on, positive current flows through chopper CH4, D2, L and E, inductance L stores energy during the time CH4 is on.
  • When chopper CH4 is turn off current is fed back to the source through D2 and D3. 
  • Here load voltages negative while load current is positive, leading to the chopper operation in the fourth quadrant. 
  • Also, the power is fed back from the load to the source side. 
  • Here  chopper operates as a step up chopper.