Potential Type Relay
A potential relay is a normally closed (NC) device, and this overcomes the problem of contacts arcing on start-up. A potential relay incorporates a coil that senses start winding voltage. As the compressor speed increases, the start winding voltage also increases. When this voltage reaches the relay’s pick-up value, the contacts open. While the compressor continues to run, the start winding voltage will remain sufficiently high to hold the relay open. When the compressor is switched off, the relay contacts close.
Suits the below Kirby Compressor
