What is a PSC motor?
A Permanent Split Capacitor (PSC) Motor is a type of single-phase AC motor; more specifically, a type of split-phase induction motor in which the capacitor is permanently connected (as opposed to only being connected when starting).
AC motors can be divided into single- and three-phase motors depending on whether they are driven by a single or three-phase power supply.
A number of different types exist for single-phase induction motors. One of these involves using a capacitor to generate a magnetic field in such a way that it simulates a second power supply phase, thereby generating the torque needed to start the motor rotating. Such motors are called “capacitor start motors” to reflect the use of a capacitor for this purpose. The category also includes motors in which the capacitor remains connected at all times (not just when starting) and these are called “capacitor run motors” or “permanent capacitor motors”.
ONSTRUCTION OF PERMANENT SPLIT CAPACITOR MOTOR
Like other Single Phase Induction Motor, permanent Capacitor Motor also has rotor cage. It has two windings : main winding and auxiliary (starting) winding. One Capacitor is connected in series with the starting winding. It is permanently connected in circuit during both running and starting conditions.
|CIRCUIT DIAGRAM OF PSC MOTOR AND TORQUE-SLIP CHARACTERISTICS|
Since the capacitor is permanent, so NO CENTRIFUGAL SWITCH IS USED IN THIS TYPE OF MOTOR.
Such type of motor provides uniform torque and has noise free operation.
Working of Permanent Split Capacitor Motor is based upon the Double field Revolving Theory(click to read). Basically working of every type of Single Phase Induction Motor is based upon this theory.
ADVANTAGES OF PSC MOTOR
No centrifugal switch is required.
Efficiency is high.
As the capacitor is connected permanently in the circuit, the power factor is high.
It has a higher pullout torque.
LIMITATIONS OF PSC MOTOR
The paper capacitor is used in the motor as an Electrolytic capacitor cannot be used for continuous running. The cost of the paper capacitor is higher, and size is also large as compared to the electrolytic capacitor of the same ratings.
It has low starting torque, less than full load torque.
Used in fans and blowers in heaters and air conditioners.
Used in refrigerator compressors.
Used in office machinery.