Types of single-phase motors are distinguished mostly by the way they are started and the torque they develop.
Shaded Pole motors
have low starting torque, low cost, low efficiency, and no capacitors. There is no start switch. These motors are used on small direct drive fans and blowers found in homes. Shaded pole motors should not be used to replace other types of single-phase motors.
Permanent Split Capacitor motors
have applications similar to shaded pole, except much higher efficiency, lower current (50% - 60% less), and higher horsepower capability. PSC motors have a run capacitor in the circuit at all times. They can be used to replace shaded pole motors for more efficient operation and can be used for fan-on-shaft fan applications, but not for belted fans due to the low starting torque.
Split Phase motors
have moderate to low starting torque (100% - 125% of full load), high starting current, no capacitor, and a starting switch to drop out the start winding when the motor reaches approximately 75% of its operating speed. They are used on easy-to-start belt drive fans and blowers, as well as light-start pump applications.
Capacitor Start motors
are designed in both moderate and high starting torque types with both having moderate starting current, high breakdown torques.
Moderate-torque motors are used on applications in which starting requires torques of 175% or less or on light loads such as fans, blowers, and light start pumps. High-torque motors have starting torques in excess of 300% of full load and are used on compressors, industrial, commercial and farm equipment. Capacitor start motors use a start capacitor and a start switch, which takes the capacitor and start winding out of the circuit when motor reaches approximately 75% of its operating speed.
Moderate-torque motors are used on applications in which starting requires torques of 175% or less or on light loads such as fans, blowers, and light start pumps. High-torque motors have starting torques in excess of 300% of full load and are used on compressors, industrial, commercial and farm equipment. Capacitor start motors use a start capacitor and a start switch, which takes the capacitor and start winding out of the circuit when motor reaches approximately 75% of its operating speed.
Capacitor Start/Capacitor Run motors
have applications and performance similar to capacitor start except for the addition of a run capacitor (which stays in circuit) for higher efficiency and reduced running amperage.
Generally, start/ capacitor run motors are used for 3 HP and larger single- phase applications.
Generally, start/ capacitor run motors are used for 3 HP and larger single- phase applications.