Question

The motor used for the compressors is

• A. DC series motor
• B. Capacitor start capacitor run motor
• C. Shaded pole motor
• D. Reluctance motor

Hint:

For heavy, single-phase loads starting under pressure (like compressors and water pumps), a Capacitor-Start Capacitor-Run motor is the standard choice to handle both high starting torque and running efficiency.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Compressors (such as those in refrigerators and air conditioners) operate under high load and require unique electric motor performance characteristics:
- High starting torque to overcome initial backpressure.
- High operating efficiency and a high power factor during continuous operation.

Step 2: Detailed Explanation:
Let us evaluate the electric motor options:
- DC Series Motor: This motor provides exceptionally high starting torque, but its speed varies significantly with load, and it is not suited for standard AC-powered domestic/industrial compressors.
- Capacitor-Start Capacitor-Run Motor: This single-phase induction motor uses two capacitors:
1. A start capacitor (high capacitance) in series with the auxiliary winding to produce a large phase shift, providing the high starting torque required to start the compressor against pressure.
2. A run capacitor (lower capacitance) that remains in the circuit during operation to optimize the power factor, reduce current draw, and improve running efficiency.
This makes it the ideal choice for compressors.
- Shaded Pole Motor: This motor has very low starting torque and low efficiency, and is only used for small fans.
- Reluctance Motor: This is a synchronous motor used in low-power, constant-speed applications (like timers), and is unsuitable for heavy compressor loads.

Step 3: Final Answer:
The motor used for compressors is the capacitor start capacitor run motor.