Single-phase motors are built differently from three phase motors that start and run in a direction based on the phase rotation of the incoming power. An auxiliary starting means is required to run single-phase motors, which, once started in a direction, will continue to run in that particular direction.
Single-phase motors are categorized by the method used to start the motor and the method used to establish the direction of rotation.
Split Phase Motors
Split phase motors are categorized under single phase and are generally available from 1/25 to 1/2 HP. They have low starting torque (turning force) and high starting current but are less expensive. Split phase motors are generally restricted to applications where the load needs low starting torque and starts are infrequent.
Capacitor motors are available in sizes from sub-fractional to 15 HP and prove to be the most popular single-phase motors on the market.
Single Value Capacitor Motors
They are also called permanent split capacitor (PSC) motors. The motor operates with a capacitor connected in series with one of the two windings. This type of motor is generally used on small sized fans, blowers, and pumps typically less than 1 HP.
Two Value Capacitor Motors
The two value capacitor motor is generally used on large blowers with 5-15 HP single phase motors. It starts as a capacitor start motor but runs as a form of a two phase or PSC motor. Therefore, large single-phase motors having high starting torques and moderate starting currents can be constructed using this combination, and at reasonable rates.