Resistive Load Modules
RATINGS
All standard modules are suitable for continuous operation at the specified ambient temperature.
Standard resistive AC load modules are available in six frame sizes with ratings between 10 kW and 1200 kW. The maximum amount of load available in any frame size is dependent on the capacity of the cooling fans and the number of resistor elements needed to give the required switching resolution.
Standard Units are designed for operation at a specified voltage and frequency. Multi-voltage, multi-frequency equipment can however be manufactured to order.
The load resistors are unaffected by change in frequency but must not be operated at voltages above the specified voltage. They may however be used at low voltages, but the total load available will be reduced.
When operating at reduced voltages the cooling fans and control circuit will require the connection of a suitable auxiliary supply.
ENCLOSURES
Enclosures are manufactured from coated mild steel sheet, folded to form a rigid IP55 construction.
Transportable models are suitable for lifting by forklift truck and are fitted with heavy duty swivel castors and lifting eyes.
When ordered for fixed installation the castors are replaced with channels for fixing to a suitable concrete base.
The standard finish is a white, oven-baked, polyester powder coating which gives a tough high gloss finish resistant to UV radiation. For installations in a corrosive or salt laden atmosphere special finishes are available.
CONTROL
The resistors are switched by contactors in order to supply a 1kW switching resolution for all ratings up to 1200 kW.
The integrated control PCB accepts signals from any of the Crestchic controllers, each of which is designed to perform a particular control function.
More than one load module may be linked by a control loop cable and operated as one load by a single controller, this facility is available as an option.
When required by the customer, simple on-board control can be fitted to switch the load in a limited number of steps by means of toggle switches or externally by customer's own control system.
COOLING
Crestchic standard load modules have forced air cooling suitable for operating in ambient temperatures up to 35 deg.c. Tropicalised versions are available allowing operation in higher ambients.
The air flow on transportable units up to 400 kW is produced by single phase motor driven fans, larger units and units for fixed installation have 3 phase motors.
Fans are controlled by DOL starters and protected by thermal overloads.
Thermal sensors will shed load should the temperature of the element chamber exceed 90 deg.c. Airflow switches are fitted on units rated in excess of 400 kW.
Stayput emergency stop push buttons are fitted to the fan circuit.
Transportable modules with 3 phase motors have a monitor circuit to prevent operation unless phase rotation is correct. Optional manual changeover switch or automatic changeover contactors are available to correct the phase rotation.
