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HVACR317 - Refrigeration

HVACR317 - Refrigeration. Split Phase Motors 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 - Refrigeration

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  1. HVACR317 - Refrigeration Split Phase Motors 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 Motors • 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. PSC Motors • PSC stands for 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. • 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.

  11. PSC Motor Example

  12. CSIR Motors • CSIR stands for Capacitor Start and Induction Run motors. • CSIR Motors 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.

  13. 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.

  14. CSCR Motors • CSCR stands for Capacitor Start Capacitor Run Motors. Can also be abbreviated to CSR (Capacitor Start and Run). • These 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.

  15. CSCR Motors • Once the motor has been started, the start capacitor must be taken out of the circuit using a switch or a relay. • These devices are called start components and will be covered in another section.

  16. CSCR Motor Diagram

  17. 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.

  18. Hermetic Motor Diagram

  19. 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

  20. Hermetic Motors Photo

  21. 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).

  22. Motors • Once you know C, check between C and the other two terminals. • The one with the highest resistance is Start (or S). • The one with the lower resistance is Run (or R).

  23. Motors • The best way 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.

  24. Motor Speeds • Motor speeds are shown in RPMs (revolutions per minute). • This is a measure of how many times per minute the shaft rotates. • Sometimes you will need to figure out RPMs for a motor.

  25. Motor Speeds • To figure motor speed, first use the motor labels. • If there is no label, use this formula: Speed (rpm) = (frequency x 120) / Poles

  26. Shaded Pole Diagram

  27. CSCR Diagram

  28. Split Phase Diagram

  29. PSC Diagram

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