GATE Electrical Engineering - Complete Master Library

 

 Page 21 – DC Chopper (Introduction)

                                         

1️⃣ What is a DC Chopper?

A DC Chopper is a DC to DC converter that converts fixed DC input voltage into a variable DC output voltage.

✔ Also called DC equivalent of Transformer
✔ Operates using high frequency switching devices (IGBT, MOSFET, SCR)

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2️⃣ Basic Principle

Chopper works by rapidly turning ON and OFF the switch.

Output voltage depends on Duty Cycle (D)

Duty Cycle (D) = T_ON / T

V_o(avg) = D × V_in

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3️⃣ Why Chopper is Needed?

• ✔ Efficient DC voltage control
• ✔ Less power loss compared to rheostat
• ✔ Used in battery powered systems
• ✔ Electric vehicles
• ✔ DC motor speed control

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4️⃣ Types of Choppers

• Step-Down Chopper (Buck)
• Step-Up Chopper (Boost)
• Type A, B, C, D, E (Based on quadrant operation)

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 GATE Important Points

• Duty cycle formula
• Average output voltage derivation
• Current ripple concept
• Continuous & Discontinuous conduction
• Quadrant classification

Very Important: Chopper is high efficiency DC voltage controller.