TEMPERATURE CONTROL WITH INTERMEDIATE REST REGION.

A zero-voltage switching temperature controller is presented. The controller is able to hold temperature steady at an intermediate level for long periods between temperature scans. Either proportional control can be selected or an increase in power duty cycle as the desired maximum temperature is approached. This controller has been applied practically to the regulation of 3 kHz induction furnace and a conventional wire-wound furnace. As most furnaces have expensive refractory linings, two fail-safe devices are incorporated, the first one within the electronic circuit, the second method of protection is by computer. A program written in FOCAL for use on a PDP-8E is shown.