Heating element control

摘要

The temperature of each heating element (10-13) among a plurality of heating elements (10-13) is regulated by opening the closing a relay (35-39) associated with each heating element in response to the monitored temperature of each heating element. The voltage across all of the relays (36-39) is interrupted simultaneously at predetermined intervals, and each relay is opened or closed only when the voltage is interrupted. This permits the use of relays having lower current ratings and also extends relay life.