Sunbeam 20060328 Service Manual page 12

Compressor start circuit - See figure B6
When the auto - heatable state relay reaches enough temperature, it changes abruptly from a low resistance (3-12
ohms) to a high resistance (10 - 20.000 ohms) and actually "switches off" the start windings. The relay does not shunt
the run capacitor any more. Now, it is seried with the start windings. The only purpose of the run capacitor is to improve
the compressor service efficiency, which is achieved by "correcting" the power factor of the compressor motor.
Compressor Operation Characteristics
1. When the compressor electric circuit is excited, the start winding current causes PTC relay heating and, after certain
starting period, it "switches off" the start winding circuit. NOTE: The PTC relay will "switch off" the start winding circuit
although the compressor has not ran (similar to a new start after a temporary electric power cut - off).
2. As the PTC relay opens compressor start circuit, whether it has ran or not, the overload protector has been mapped
out and calibrated to open the compressor electric circuit only with a winding current of blocked rotor.
σWARNING The overload protector should only be replaced by an appropriate and correct model protector.
3. With an "open" PTC relay, the compressor doesn't start because the start windings receive none or little current. The
overload protector will open due to the high rotor current of the run winding.
4. The compressor starts with a "short – circuit" capacitor or PTC relay, and the overload protector will open quickly due
to the high current lifted in the combined run and start windings.
5. The compressor will start and will work in an apparently normal way with an open or weak capacitor, but will operate
with a less efficient use of energy.
L1
Overload
6
Start
S
Run
C M
5
Motor comp.
Figure B5 – Compressor start circuit
L1
Overload
Start
S
Run
C M
Motor comp.
Figure B6 – Compressors Run Circuit
N
Run capacitor
3
2
1
PTC relay
N
Run capacitor
6 3
2
5 1
PTC relay
PAGE . B5