Quantcast Single-Phase Hermetic Motors

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The accumulator is located inside the refrigera- tion cabinet and acts as a safety device. As a safety device  it  prevents  the  flow  of  liquid  refrigerant into the suction line and the compressor. This is because  liquid  refrigerant  causes  considerable knocking and damage to the compressor. Figure 14-24 shows the location of an accumulator in a system. SINGLE-PHASE HERMETIC  MOTORS Basically, there are four types of single-phase motors  used  in  hermetic  assemblies:  the  split- phase;   the   capacitor-start,   induction-run;   the capacitor-start, capacitor-run; and the permanent split-phase.  Each  motor  is  discussed  in  this section. SPLIT-PHASE The split-phase motor is used generally on con- densing  units  of  1/10-,  1/6-,  and  1/4-horsepower Figure  14-24.—Accumulator  location. Figure 14-25.—Schematic wiring diagram of a split-phase motor  circuit. 14-16 capillary  tube  systems.  It  has  a  low  starting torque and contains both a starting winding and a running winding. A disconnect device is required for the starting winding when the motor reaches sufficient speed to operate on the running wind- ing. Figure 14-25 is a schematic wiring diagram of  a  split-phase  motor  circuit. CAPACITOR-START, INDUCTION-RUN This motor is similar to the split-phase type except  that  a  starting  capacitor  is  connected  in series  with  the  starting  winding  to  provide  higher starting   torque.   Figure   14-26   is   a   schematic diagram illustrating this type of motor. A device is  also  required  to  disconnect  the  starting  winding when the motor reaches rated speed. This motor is  commonly  used  on  commercial  systems  up  to three-fourths   horsepower. CAPACITOR-START, CAPACITOR-RUN Two  capacitors  are  used  with  the  capacitor- start,  capacitor-run  motor:  a  starting  capacitor and  a  running  capacitor.  The  capacitors  are  in parallel  with  each  other  and  in  series  with  the starting  winding.  Figure  14-27  is  a  schematic diagram illustrating this type of motor circuit. The two capacitors turn the motor power surges into two-phase  power  when  the  motor  is  started.  At approximately two-thirds rated speed, the start- ing  capacitor  part  of  the  circuit  is  disconnected by a start relay device. Only the running capacitor remains in the circuit. This type of motor has a Figure 14-26.—Schematic wiring diagram of a capacitor-start induction-run motor.



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