The model 1027 linearly controls, with respect to a command or control signal, the electrical power applied to a single-phase resistive load by distributive zero-cross operation of silicon controlled rectifiers (SCRs).
Distributive zero-cross operation implies that the supply voltage is switched on and off only when the instantaneous value of the sinusoidal supply voltage is zero and that the load power is controlled by varying the number of electrical half cycles that power is applied to and removed from the load. (See theory of operation for additional details.)
The controller depending upon the model number is capable of accepting either mA command signals, DC voltage command signals or it may be controlled by a potentiometer. Electrical isolation is provided to isolate the command signals from the line and load voltages.
Additional features of the 1027 controller include:
- Line voltage compensation, which for a given command signal, maintains the load power constant independent of line voltage variations.
- Sync-Guard, which provides a means to reproduce the synchronous operation of two or more controllers.
- Trans-Guard, which prevents saturation of supply transformers which can result from zero-cross operation.