190 likes | 374 Views
214 Motors Part II. Permanent Split Capacitor Motors. In order to increase the starting torque of a motor you can insert a capacitor in series with the start winding circuit.
E N D
Permanent Split Capacitor Motors • In order to increase the starting torque of a motor you can insert a capacitor in series with the start winding circuit. • In a PSC motor this capacitor remains in series while the motor is operating. There is no switch or relay that removes this capacitor from the circuit.
PSC Motor • Residential Condenser fan motors and residential furnace blower motors are the primary use of PSC motors.
PSC Motor • PSC motors have moderate starting torque and intermediate running efficiency. • These motors are used primarily for small compressors and direct-drive blower and fan applications.
CSIR Motors • CSIR are capacitor start and induction run motors. • They use a start cap and a start relay. • Once the motor has reached 75% of its rated speed the start capacitor is removed from the circuit.
CSIR motors • CSIR motors have a high starting torque and are used in residential and small commercial compressors. • May see them in beverage coolers or small reach ins.
CSCR Motors • CSCR (Capacitor Start Capacitor Run) motors are the same as Permanent Split Capacitor motors except they have a start capacitor wired to them. • A start capacitor is a high capacitance capacitor that will provide the motor with additional torque when starting.
CSCR Motors • Once the motor has been started it, the start capacitor must be taken out of the circuit using a switch or a relay. • These devices are called start components and this is covered in the next section. • This motor can be abbreviated to CSR. (Capacitor Start and Run).
Motors • If the windings are not marked use your ohm meter and check resistance. • Check between all three windings. • The winding measurement with the highest resistance is between start and Run (S and R). The remaining terminal is Common ( or C).
Motors • Once you know C check between C and the other two terminals the one with the highest resistance is S (or Start). • The one with the lower resistance is Run (or R).
Motors • Best way to do this is to write down C, S, R in a triangle on a piece of paper and make sure you write down each measurement. • If you have any doubt - go back and do it again.
Motor Speeds • Motor speeds are shown in RPM’s • RPM is revolutions per minute. This is a measure of how many times per minute the shaft rotates. • Sometimes you will need to figure out RPM’s for a motor.
Motor Speeds • To figure motor speed first use the motor labels • If no label is found use the formula: • Speed (rpm) = (frequency x 120) / Poles
CSCR Diagram R C S
Split Phase Diagram R C S
PSC Diagram R C S