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HVAC drives incorporate a fire mode
Published:  26 April, 2013

Following the recent launch of its CFW500 variable-speed drive, WEG has announced a variant dedicated to HVAC pump and fan duties. The compact, easy-to-use CFW501 drives span the power range 0.187.5kW and there are plans to increase this to 22kW next year.

One special HVAC function is a fire mode that prevents the motor from stopping when critical operating conditions are detected, such as high internal temperatures. This makes the drives suitable even for demanding applications such as smoke extraction. Conformal coatings protect the circuit boards against dust, moisture and chemicals.

The drives can identify load problems such as dry pumps and broken belts, while a sleep mode optimises motor usage and avoids very low speeds. They can monitor PTC thermal sensors and are protected against short cycles. A bypass function allows users to power the motor directly from the mains.

The CFW501 uses the same modular plug-and-play structure as the CFW500 and offers a built-in HMI and a micro-PLC that is programmed in accordance with IEC 61131-3. The interface supports HVAC engineering units such as bar, mbar and m3/h, and is available in a remotely controlled version for installation in a panel door. The drives support the BACnet, MetaSys N2 and Modbus-RTU protocols used in building automation. They can also connect to fieldbus systems such as Profibus-DP, DeviceNet and CANopen, using plug-in modules.

Both, scalar (V/f) and vector control methods are available. The inverters offer three PID controllers a main one to control the process, and two others which control independent process variables. Depending on the motor speed and load conditions, a power-saving function can reduce the flux, thus decreasing losses and improving energy efficiency.