Chopper Classification
Diagram and operation of Chopper is described on this section based on which quadrant does each chopper operates.
Summary
Diagram and operation of Chopper is described on this section based on which quadrant does each chopper operates.
Things to Remember
1) Chopper are classified into different classes on the basis of the directions of the current and voltage flow.
2) Class A, Class B, Class C, Class D and Class E are the few category of Chopper classification.
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Chopper Classification
Chopper Classification
Chopper are classified into different classes on the basis of the directions of the current and voltage flow. Thus,dc chopper are classified into following five types:
1)First quadrant Converter/Class A Chopper
The operation of this type of chopper is limited to first quadrant. When the chopper is on, the load current flows into the load and output voltage is equal to the supply voltage. When the chopper is off, the load current flows into the load through Freewheeling Diode
2)Second Quadrant Converter/Class B Chopper
The operation of this type of chopper is limited to second quadrant. When the chopper is On, the load current flows out of the load through switching device[i.e IGBT/Power Transistor]and output voltage is nearly equal to the zero. When the chopper is off, the load current flows out of the load through Diode and output voltage is equal to the Load Voltage and it is supplied to the voltage source .And it is operated as inverter.
3) Class C Chopper
The operation of this type of chopper lies on the first and second quadrant. And this type of chopper is the combination of class A and Class B converter in a suitable way. CH1 and D2 are the power electronics device which is used to simulate the operation of the First Quadrant Chopper and CH2 and D4 are the other devices which is used to simulate the operation of the Third Quadrant Chopper. So, in this chopper, Even though Load Voltage is positive but load current can be both positive(into the load) or negative(flows out of the load).And the most important point is CH1 and CH shouldn’t be trigerred at the same instant of time otherwise it may destroy the circuit.
4 )Class D Chopper
When both CH1 and CH2 ar triggered simultaneously, the output voltage voltage Vo = V and output current flows through load. When CH1 and CH3 are turned off, the load current continues to flow in the same direction through D1 & D2 due to energy stored in inductor L.. Average Load voltage is positive if On time is greater than off time. Hence, the directon of current is always positive but load voltage can be positive or negative. Thus, it’s operation lies on the first and fourth quadrant.
5)Class E Chopper
It is the combination of Class C Chopper and Third and fourth Quadrant Converter. A table is presented is below which represents the state of different power devices to be in different quadrants of operation:
| Quadrant | Required Power Electronics Devices And Their State |
| First | S1(modulating),S2(continuously on) and D4 as freewheeling Diode |
| Second | S4(modulating),S2(continuously on) and D1 |
| Third | S3(modulating),S4(continuously on) and D2(Polartiy of the battery must be reversed) |
| Fourth | S2(modulating) ,D3and D4(Polartiy of the battery must be reversed) |
References
1) B Classes. CHOPERS(DC-DC Converters). n.d. 10 05 2016. <http://www.bclasses.in/images/material/eee/powerelectronics/newdcchoppers/63.jpg>.
2) B Classes. CHOPERS(DC-DC Converters). n.d. 10 05 2016. <http://www.bclasses.in/images/material/eee/powerelectronics/newdcchoppers/60.jpg>.
3) electrical4u. chopper-dc-to-dc-converter. n.d. 15 05 2016. <http://www.electrical4u.com/images/type-b-chopper.png>.
Lesson
DC Chopper
Subject
Electrical Engineering
Grade
Engineering
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