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HVACR317 – Core for Refrigeration

HVACR317 – Core for Refrigeration. Motors Split Phase PSC CSIR CSCR. Split Phase Motors. Split phase motors are also called induction start - induction run motors. These motors use a current relay or a centrifugal switch to remove the start winding from the circuit.

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HVACR317 – Core for Refrigeration

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  1. HVACR317 – Core for Refrigeration Motors Split Phase PSC CSIR CSCR

  2. Split Phase Motors • Split phase motors are also called induction start - induction run motors. • These motors use a current relay or a centrifugal switch to remove the start winding from the circuit. • The start windings work on a phase shift principle.

  3. Split Phase Motor • The voltage from the start winding to the run winding is 10 degrees out of phase. • Starting torque and running torque are relatively low in split phase motors because the phase shift is so low.

  4. Split phase motors • These motors are used for belt drive blower applications such as small appliances like: • Washers • Dryers • Dish washers • Some older furnace blowers

  5. Split Phase Motors

  6. Split Phase Motor • The centrifugal switch removes the start winding from the motor circuit once the motor reaches around 75% of its rated speed. • This is the part that most often fails when a motor is started and stopped many times.

  7. Centrifugal Switch • The switch is normally closed when the motor is not operating.

  8. Centrifugal Switch

  9. 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.

  10. PSC Motor • Residential Condenser fan motors and residential furnace blower motors are the primary use of PSC motors.

  11. 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.

  12. PSC Motor Example

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. CSCR Motors • This motor can be abbreviated to CSR. (Capacitor Start and Run).

  18. CSCR Motor Example

  19. Hermetic Motors • Hermetic motors are single phase up to about 5 hp (horsepower). • Hermetic motors are those found inside the compressor shells. • They are wired the same way as any other split phase motor, but the start components must remain outside the compressor shell.

  20. Hermetic Motors

  21. Hermetic Motors • On the outside of the compressor shell there are three terminals. Most of the time these have some markings on them. • They are labeled C, R, S • S = Start winding • C = Common • R = Run Winding

  22. Hermetic Motors

  23. 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).

  24. 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).

  25. 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.

  26. 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.

  27. 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

  28. Shaded Pole Diagram C R

  29. CSCR Diagram R C S

  30. Split Phase Diagram R C S

  31. PSC Diagram R C S

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