What is the difference between running capacitor and starting capacitor
The main differences between a running capacitor and a starting capacitor lie in their purpose, design, and how they function in an electric motor, particularly in single-phase induction motors. Here's a breakdown of their differences:
**1. Purpose:**
**Starting Capacitor:**
- Provides an initial boost of torque to start the motor.
Only used during the starting phase of the motor to help it reach the correct speed.
**Running Capacitor:**
Improves the running efficiency and performance of the motor once it starts.
- Remains connected to the motor circuit while the motor is running.
**2. Design and Capacitance Value:**
**Starting Capacitor:**
Has a higher capacitance value (measured in microfarads, µF) compared to a running capacitor.
- Typically ranges from 70 µF to 500 µF or more, depending on the motor size.
- Designed to handle a short burst of energy during startup.
**Running Capacitor:**
Has a lower capacitance value, usually ranging from 5 µF to 50 µF.
- Designed for continuous operation and can handle lower currents over a prolonged period.
**3. Physical Characteristics:**
**Starting Capacitor:**
Larger in size and usually enclosed in a plastic or aluminum housing.
- Electrolytic type, making them capable of storing a large charge quickly.
**Running Capacitor:**
Smaller in size and often enclosed in metal housings.
- Non-electrolytic, usually of oil-filled or metallized film type, which allows for continuous duty.
**4. Connection and Operation:**
**Starting Capacitor:**
Connected in series with the motor's start winding and switched out of the circuit (disconnected) once the motor reaches about 75% of its full speed, often by a centrifugal switch or relay.
**Running Capacitor:**
- Connected in series with the motor’s auxiliary (start) winding but remains in the circuit during operation.
**5. Failure Impact:**
**Starting Capacitor:**
Failure can result in the motor failing to start or struggling to start with lower torque.
**Running Capacitor:**
Failure can cause reduced running efficiency, increased current draw, overheating, or even motor stalling.
**Summary:**
**Starting capacitors** help the motor start by providing an initial torque boost but are disconnected after startup.
**Running capacitors** help the motor run efficiently by improving its power factor and reducing power consumption, staying connected throughout operation.
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