Control Concepts: 3021B Three Phase Power Controller

May 26, 2020

The model 3021B is a two-leg zero-cross SCR power controller that linearly controls, proportional to a command signal, the power applied to a 3 phase electrical load. Command signals may be 0-5Vdc or 0-10Vdc or a potentiometer. The controller is available with current ratings of 10, 20, 30, 40 or 70 Amps and voltage ratings of 120, 240, 480 or 575 Vac, 50/60hz.

The controller consists of a master and a slave assembly. Each assembly consists of a heatsink and an SCR (Silicon Controlled Rectifier) module containing two SCRs configured to operate as a zero-cross AC switch. The SCR module also provides electrical isolation between the line and load voltage and the heatsink and the input command to the SCR module.

An electronic circuit on the master assembly controls the ON/OFF switching of the SCR modules causing the load power to be directly proportional to the command signal. The fast ON/OFF zero-cross switching improves heater life and provides superior performance over that achieved by relays, contactors or other solid state time proportional controls.

The 3021B features Sync-guard which reduces synchronous operation of multiple SCR controllers. Up to 10 of these controllers may be wired together to reduce voltage variations caused by multiple controllers cycling on and off at the same time.

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