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  • PR3-O-300KW
01704 516500
12.00 KGS

Product Description

The PR3 range of thyristor stacks provides full seamless control of three phase resistive loads for 325kW and 450kW, using two thirds control technique. Signal control is by a DC signal. These burst firing control stacks use fast pulse zero volts switching technology, to minimise flicker and eliminate RFI problems. They also incorporate an automatic resetting temperature trip, integral semiconductor fuses and heatsink. All are forced-air cooled and have easy access to signal & power terminals for simple installation.


Suitable for the Heating, Ventilating and Air Conditioning (HVAC) market for air curtain applications, but also for furnaces, ovens, dryers and hot plates.

Cooling Requirements

This robust stack assembly has an operational temperature of 65°C when naturally cooled and has a built in 90°C over temperature trip on the heatsink as a safety feature. The 230V AC Fan will always be on in normal working conditions. The unit should be mounted vertically, with heatsink fins running top to bottom, also with the fan at the bottom (so the airflow is upwards) and with sufficient surrounding air space to maximise natural convection cooling. [Note: the unit can be mounted with the fan at the top, if the fan is removed and re-fitted so that the airflow is drawing air from the heatsink]. If the unit is mounted in an enclosure or cabinet, adequate ventilation and/or additional forced air-cooling (a fan) should be considered for the cabinet.

Load Considerations

The PR3 series of power controllers are designed for resistive type loads, e.g. Heaters. Unusual heating loads such as Molybdenum, Platinum or Tungsten have a typical, 10:1, hot to cold, resistance ratio and therefore, when cold, draw larger currents than normal.


This unit has simple clamp-type connectors for all auxiliary wiring requirements.  


It is recommended that fast acting semiconductor type fuses (as supplied) be used for protection. See SRA Data sheet X10255 for further information.

CE Marking

This family carries a “CE” marking. These burst fire controllers do not normally require a remote filter. For more information see recommendations section and contact our sales desk.   See Declaration of Conformity.

logo-pdf.gifClick here to download specification sheet X10712




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