The PR3-E S/SP/SPM range of thyristor stacks provide full, seamless control, of three phase, resistive loads using a two thirds control technique. Control of the power level is either by a dc signal or by manual control using a 5kΩ potentiometer. The PR3-E burst firing control stacks use fast pulse, zero volts switching technology, to minimise flicker and eliminate RFI problems. The controllers also incorporate an automatically resetting temperature trip, integral semiconductor fuses, and an integral volt free trip/enable input for wiring of an external thermal trip. The range contains two power ratings: 27kW and 36kW. For each power rating, three versions are available: S(standard – without high speed (HS) fuses and without internal power supply), SP (Standard Plus – including HS fuses and internal power supply) and SPM (Standard Plus Monitoring) version – including HS fuses, internal power supply and SCR/HS Fuse monitoring). All have easy access to signal & power terminals for simple installation.
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.
This input should be driven by a volt free contact. When the contact is closed the unit is enabled to supply power to the load. When the contact is open this disables the power to the load. If this input is not used a wire link must be fitted to enable the unit.
Alarm Relay Output (3-way terminal – Volt Free Contacts, Normally Open (NO), Normally Closed (NC), Common (COM).
The alarm circuit has voltage free relay contacts which have a 2A@125 V AC RMS rating. The alarm conditions which are detected are phase loss (L1, L2, L3), fuse failure (L1, L3), device failure (L1, L3), over temperature and temperature sensor error. The power to drive the alarm relay coil is obtained from the board power supply, which can be either internal or external. L2 & L3 are used to power the internal, transformer based power supply, therefore when internally powered the loss of phase L2 and L3 condition cannot be indicated as this results in a loss of power to the controller card.
Over Temperature Protection
When a heatsink temperature of above 90ºC is detected by the sensor, the alarms relay changes state and the Fault LED pulses rapidly. The power to the load will be disconnected and will not be re-enabled until the temperature drops to 85ºC.
Temperature Sensor Loss
If the temperature sensor fails or becomes disconnected, the Fault LED changes to ON/OFF (fast pulsing) and the alarm relay state changes.
Phase Loss with Auxiliary Supply
When any one of the three phase inputs is not present, the relay changes state and the Fault LED flashes with ON/OFF bursts of 1.5 seconds. This is only functional with a remote supply (see below).
SCR/Fuse Monitoring (SPM model only)
Fault and Status LED flash alternately and the alarm relay will change state. This condition indicates that either a HS fuse has failed or a SCR open or short circuit failure has been detected.