WEG, a leading supplier of drive technology, power generation and automation solutions, has enhanced the functionality of the CFW701 frequency inverter for demanding heating, ventilation and air-conditioning (HVAC) applications with the addition of a manual/automatic override.
An integrated motor protection switch gives the new system, consisting of a cabinet unit fitted with a CFW701 frequency inverter, redundant motor protection for consistently reliable operation, says a company spokesman.
“In case of a frequency inverter defect or outage, the output relay of the CFW701 connects the motor directly to the mains through an external bypass circuit. A switch on the front of the cabinet unit allows the user to configure the bypass function for either manual or automatic switching to bypass mode in the event of a fault,” he adds
He says this stand-alone system is primarily suitable for the reliable and energy-efficient control of induction motors, used to drive pumps or fans in HVAC installations in hospitals, airports, office buildings, hotels, shopping centres or other facilities.
The CFW701 is equipped with an integrated maintenance switch to allow the frequency inverter to be replaced, tested or programmed while the motor continues operating through the bypass. The controls on the front of the cabinet unit allow users to issue start and stop commands over the frequency inverter as well as the bypass circuit.
The improved inverter has a built-in fused disconnect switch, eliminating the need for additional protection components such as circuit breakers or fuses. The package also has high short circuit capacity without additional components covering a range of 35 to 100 kA.
Control and power sections for the CFW701 are located in the cabinet unit below the frequency inverter to prevent accidental user contact with live components during operation. All components of the system come from WEG’s automation products portfolio and comply with the UL508a standard. The enclosure protection rating is IP20 in the standard version.
The CFW701, featuring a PLC (programmable logic control) and integrated HMI (human machine interface), is suited to HVAC applications in the 5.5 to 110 kW power range. The user-friendly display is also able to show specific physical units such as bar, mbar and cu m per hr. Furthermore, the frequency inverter software incorporates three integrated PID controllers for enhanced process monitoring and higher accuracy.
A special fire mode prevents motor shutdown when critical operating conditions, such as internal device over-temperature, are detected by the frequency inverter. The fire mode will be typically used for demanding applications like smoke extraction fans and exhausters.
Even in the basic configuration, the CFW701 provides interfaces for integration with the most commonly used building automation communication systems, such as Bacnet, MetaSys N2 and Modbus RTU. The device’s plug-and-play design enables extremely easy installation and commissioning. The CFW701 with integrated bypass function also utilises the full potential of speed and frequency control to maximise the efficiency of the controlled motor.