SKU A437442-HV Category

Three Phase – Enclosed

£489.25 ex. VAT

Quantity discounts
1-4 5-9 10-19 20+
£489.25 £464.79 £441.55 £419.53


Introducing the PR3 Thyristor Stack Range, designed for seamless control of three-phase resistive loads with advanced features for optimal performance and safety. Utilizing a two-thirds control technique, these stacks offer precise control via either a DC signal or manual adjustment using a 5k potentiometer.

Equipped with burst firing control and fast pulse zero volts switching technology, the PR3 stacks minimize flicker and eliminate RFI (Radio-Frequency Interference) issues. They feature automatic resetting temperature trips, integral semiconductor fuses, and a built-in heatsink for efficient heat dissipation.


Ideal for various 3-wire, 3-phase configurations including floating-star or closed-delta setups, the PR3 thyristor stacks find extensive use in:

  • Heating, Ventilating, and Air Conditioning (HVAC) systems
  • Furnaces
  • Ovens
  • Dryers
  • Hot plates
  • Air curtain applications


  • Seamless Control: Enables precise control of three-phase resistive loads.
  • Fast Pulse Zero Volts Switching: Minimizes flicker and eliminates RFI problems.
  • Automatic Over-Temperature Protection: Ensures safety by disconnecting power to the load when the heatsink temperature exceeds 90ºC, with automatic reconnection below 85ºC.
  • Temperature Sensor Monitoring: Alerts users in case of sensor failure through continuous LED indicator pulsing.
  • Alarm Relay Functions: Includes a voltage-free relay with 3-way terminal connections for alarm notifications.
  • Integral Semiconductor Fuses and Heatsink: Ensures reliable performance and durability.

Key Functions:

  • Alarm Relay: Equipped with a voltage-free relay with a 3-way terminal (NO_NC_C) for alarm functions, providing up to 2A @ 125V AC load capacity.
  • Over Temperature Protection: Automatically disconnects power to the load when the heatsink temperature exceeds 90ºC, indicated by continuous rapid pulsing of the status LED. Power is reinstated once the temperature drops below 85ºC.
  • Temperature Sensor Loss: The status LED indicates sensor failure with continuous equal ON/OFF pulsing, ensuring prompt identification of sensor issues for maintenance.

Enhance the efficiency and safety of your electrical systems with the PR3 thyristor stacks. Designed for reliability and precision control, these stacks are the ideal solution for demanding industrial and commercial applications.

Additional information

Download the technical document for this product below.

Download Technical Datasheet
Weight 3.564 kg
Technical Support
customer service United Automation

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