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Self-Contained Flaked Ice Maker Service Manual
Publication Number: 166240010SER - 8 - © 2004, IMI Cornelius Inc.
Potential Relays
The potential relay is used as a compressor starting relay, The contact in the potential relay is N.C. The
magnet coil is connected across (parallel) the start winding and is affected by induced voltage, generated
by the start winding. As the compressor comes up to design speed, the voltage across the relay coil
increases and at running speed is sometimes as much as 2 1/2 times the supply voltage. This voltage
sets up a magnetic field which causes the relay to operate. The starting relay is calibrated to remove the
start capacitor (open the starting circuit) at approximately 85% of the motor design speed.
NOTE: BOTH TYPES OF RELAYS ARE DESIGNED TO OPERATE WITHIN VERY NARROW LIMITS
OF VOLTAGE AND CURRENT DICTATED BY MOTOR DESIGN, THEREFORE, WHEN MAKING A
REPLACEMENT OF A RELAY ALWAYS PROVIDE AN EXACT REPLACEMENT, RECOMMENDED
BY THE COMPRESSOR MANUFACTURER.
Capacitors - General
An electrical capacitor is a device which stores up electrical energy. Capacitors are used with single
phase motors to provide starting torque and improve running characteristics; by feeding this energy to
the start winding in step with the run winding.
Any capacitor has three (3) essential parts, two (2) of which are usually foil plates separated and
insulated by the third part called the dielectric.
Two general types of capacitors are used with electric motors. The electrolytic starting capacitor usually
uses a very thin film of oxide on the metallic plate as the dielectric. The running capacitor usually is of the
liquid filled type.