Thyristor Power Regulators, Zero Crossing Type, are similar in general functions to solid-state relays. There are, however, important differences. THETA Zero Crossing Power Regulators are based on thyristors, not triacs. Thyristors are considerable more rugged and failure resistant than triacs.

These power regulators switch on the power only at the instant the supply voltage crosses zero volts (when the direction of current flow changes, typically 100 times a second for 50 Hz supply frequency). Because of this “zero crossing” control, the minimum switching period (on or off) is ½ cycle.

• Accepts pulse input.
• Control is achieved by “ON” time to ‘OFF’ time ratio of power fed to electrical heater
  
  
  

PHASE ANGLE CONTROL:

Thyristor Power Regulators, Phase Angle Type, are more sophisticated than zero-crossing power regulators, and provide more accurate temperature control. In this type of regulator, the power the on/off time of power switching can be controlled within a fraction of an AC current cycle. For a 50 Hz AC supply one cycle is of 20 mSec (milliseconds) duration, and ½ cycle is of 10 mSec duration. A phase angle power regulator can adjust the on/off time ratio within each ½ cycle.


Phase angle regulators provide the highest temperature control accuracy, and exert the least amount of stress on heater elements, of the entire power control element types. THETA Phase Angle Power Regulators also use rugged thyristors (not triacs). They have additional functions built in, e.g.: current/power limiting, overcurrent trip protection, etc.

• Accepts 4-20mA or 0-10V input.
• Control is achieved by varying conduction angle from 0 to 100. (Conduction angle is the fraction of cycle during which thyristror conduct.)
  
  
  
  Theta BTC PID controller supplies 4-20mA or 0-10V to Power Regulator.