Question

What is the difference between a capacitor start and a capacitor run motor?

Answer 1

The main difference between a capacitor start and a capacitor run motor lies in how the capacitor is used and the role it plays during the motor's operation:

1. Capacitor Start Motor:

1. Purpose: The capacitor is used to help start the motor.
   

1. Operation: When the motor is turned on, the capacitor is temporarily connected to the start winding of the motor, giving it a boost to start turning. Once the motor reaches a certain speed (about 70-80% of its full speed), a centrifugal switch or relay disconnects the capacitor from the circuit, and it runs as a regular motor.
   

1. Application: These motors are typically used in applications where high starting torque is needed, such as in air compressors, pumps, or fans.
   

2. Capacitor Run Motor:

1. Purpose: The capacitor stays in the circuit continuously during the motor's operation to improve efficiency and reduce energy loss.
   

1. Operation: The capacitor is permanently connected to the motor's start winding, which helps to smooth out the current and improve the motor's running performance. It helps maintain a higher power factor and ensures better efficiency, especially at full speed.
   

1. Application: These motors are typically used in applications where continuous running efficiency is more important than high starting torque, such as in HVAC systems, small pumps, and fans.
   

Key Differences:

1. Capacitor Start:
   

  - Capacitor only helps at the start (temporary).
  - High starting torque, but lower efficiency during running.
  - Disconnected once the motor reaches speed.
  

1. Capacitor Run:
   

  - Capacitor stays in the circuit during the entire operation.
  - More efficient during continuous operation.
  - Lower starting torque compared to capacitor start.

In summary, a capacitor start motor is designed for applications that require high torque to start, while a capacitor run motor is designed for continuous, efficient operation.