The PR3 range of thyristor stacks provides full seamless control of three phase resistive loads, 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. This build is the 500kW model, which has easy access to signal & power terminals for simple installation.

APPLICATIONS

Suitable for 3-wire, 3-phase floating-star or closed-delta configured resistive loads. This includes the Heating, Ventilating and Air Conditioning (HVAC) market for air curtain applications, but also for furnaces, ovens, dryers and hot plates.

INSTALLATION

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 unit should be mounted vertically, with heatsink fins top to bottom, and with sufficient surrounding air space to maximise natural convection cooling. If the unit is mounted in an enclosure or cabinet, adequate ventilation and/or forced air-cooling should be fitted. This PR3-E – range have forced air cooling fans fitted, which are designed to be permanently “on” when in use.

Load considerations

The PR3 series of power controllers are designed for 3-wire, 3-phase floating-star or closed delta configured resistive loads. The PR3 series are 2-leg thyristor controllers and therefore unsuitable for 4-wire, 3-phase with star point to neutral configured loads. For further information on configured loads, see the ‘Application circuits’ section of our supporting datasheet – APC (ref. X10322).

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.

Connections

This unit has Power terminals and simple clamp type terminal connectors for all auxiliary wiring requirements (see SPECIFICATIONS below).

NOTE:     It is factory set for an internal power supply. For alternative ‘voltage free’ alarm supply details see Functions section. Please contact our Technical support for further details.

Fusing & over temperature

It is recommended that fast acting semiconductor type fuses (as supplied) be used for protection. See SRA Data sheet X10255 for further information. It is recommended that a load break switch and a contact breaker is installed in the load supply. The supply to the contactor coil should be interrupted by an over-temperature thermostat located in the heater battery and also upon detection of airflow loss.

CE Marking

This family carries a “CE” marking. These burst fire controllers do not normally require a remote filter. For more information contact our sales desk.   A Declaration of Conformity is available on request.

Click here to download specification sheet