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    Working Principle & Applications of Power Regulator

    A power regulator is a panel-mounted power adjustment unit that uses a thyristor (also called Silicon Controlled Rectifier or SCR) and its trigger control circuit to adjust the load power. Thanks for its small size, high efficiency and durable service life, it is widely used in AC and DC motor speed control system, power control system, follow-up system, temperature control and many other sectors. SCR power regulator works by means of an intelligent digital control circuit. Its precise control of voltage, current and power makes for precise temperature control. And its advanced digital control algorithm greatly improves energy efficiency, which highlights its important role in saving electric energy. Power regulators are becoming an indispensable equipment in the automation industry.

    Working Principle

    Three-phase power regulator is an economical and reliable power regulator, which is composed of a trigger board, a special radiator, a fan, and a casing. The core part consists of a control board and a silicon controlled module, and the heat dissipation system is based on a plug-in highly-efficient radiator and a low-noise fan. For now, ATO offers four types of SCR power regulators with optional rated current and rated power for your selection.Three-phase SCR power regulators offer different levels of rated current when assembled with 3 wires or 4 wires.

    SCR power regulator

    The three-phase power regulator can achieve voltage regulation and power regulation by triggering SCR with the help of a digital circuit. Voltage regulation is realized through phase-shifting control, while power regulation has two methods: Fixed-cycle power regulation and variable-cycle power regulation. The control board is featured with a phase-locked loop synchronization circuit, automatic phase identification, phase loss protection, power-on slow start, slow shutdown, radiator over-temperature detection, constant current output, current limit, overcurrent protection, serial working status indication, etc. The control board can be triggered in two ways: Directly triggering the SCR module or triggering the phase-shifting solid relay. Built-in alarm buzzer can easily activate audible alarm without any additional wiring.

    SCR Power Controller Circuit
    The thyristor AC power regulator controls the output power by controlling the number of AC frequency waves in a fixed period or a variable period. The thyristor is switched on when the sine wave crosses zero, and is switched off when the sine wave crosses zero again, thus producing a complete sine wave. The fixed-cycle thyristor AC power regulator uses thyristor as a zero-voltage contactless switch. Within a fixed period T (for example, one second), the output AC frequency is changed so as to control the output power, that is, the output power varies with the frequency within a certain period. Its output waveform is shown as the following picture:

    fixed cycle scr ac power regulator output waveform
    The sine wave output generated from the variable-cycle thyristor AC power regulator is evenly distributed, and it is also called interval power regulator, where the repetition period is arranged at the smallest sine wave interval, for example, the minimum period arises when the output power is 50%, which is 40 milliseconds (0.04 seconds), that is, one waveform comes into being, and the previous one disappears. The period reaches its largest value at the maximum and minimum output power. For example, when the output power is 99.9%, the period is 20 seconds, which means 999 waveforms are turned on and turned off. One cycle, the output power is 0.1%, and the cycle is also 20 seconds, that is, one cycle is turned on and 999 cycles are turned off.

    variable cycle scr ac power regulator output waveform
    The power regulator is compatible with an intelligent PID regulator or PLC with rated voltage of 0-5V and rated current of 4-20mA (as with 3-phase 4-wire SCR power controller). Its load types include three-phase resistive load, three-phase inductive load and three-phase transformer load, and three-phase load involves central grounded load, central ungrounded load, inner triangular load and outer triangular load.


    Thyristor power regulators are widely used in the following fields:

    1. Electric furnace industry: Annealing furnace, drying furnace, quenching furnace, sintering furnace, crucible furnace, tunnel furnace, melting furnace, chamber electric furnace, pit electric furnace, melting electric furnace, rolling electric furnace, vacuum electric furnace, trolley electric furnace, quenching electric furnace, aging electric furnace, hood electric furnace, atmosphere electric furnace, oven, experimental electric furnace, heat treatment, resistance furnace, vacuum furnace, mesh belt furnace, high temperature furnace, kiln , electric furnace, etc.
    2. Machinery and equipment: Packaging machinery, injection molding machinery, heat shrinking machinery, extrusion machinery, food machinery, tempering facilities, plastic processing, infrared heating, etc.
    3. Glass industry: Glass fiber, glass forming, glass melting, glass printing, float glass production line, annealing tank, etc.
    4. Automotive industry: Spray drying, thermoforming, etc.
    5. Energy-efficient lighting: Tunnel lighting, street lighting, photography lighting, stage lighting, etc.
    6. Chemical industry: Distillation and evaporation, preheating system, pipeline heating, petrochemical industry, temperature compensation, etc.
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