AC drive controls multiple pumps

Paul Boughton
WEG is launching the CFW-08 Multi-pump AC drive that is claimed to save energy in pumping systems by enabling up to four pumps to be controlled from one variable-frequency drive (VFD). Graham Johnson, senior drives engineer at WEG UK, comments: "There are multiple advantages to installing a Multi-pump variable frequency drive system. These include energy saving, extended operating system life, system default diagnosis, constant line pressure and pump operation time equalisation."
By controlling up to four pumps simultaneously, the WEG CFW-08 Multi-pump system enables constant pressure to be maintained in pipelines regardless of fluctuations in outflow demand. This is achieved using a PID controller in conjunction with the auxiliary pumps' start/stop logic. In addition, the CFW-08 also monitors the pressure and level of the capture reservoir, and provides minimum output pressure fault monitoring for broken pipes or cavitation, and maximum output pressure fault monitoring for blocked or obstructed pipes.
The CFW-08 operates in two control modes, variable frequency (V/F) and sensorless vector. V/F mode is suited to variable torque loads and includes a selectable energy saving feature that reduces motor losses when operating at lower speeds. It is this control mode that enables the drives to operate in multi-motor applications where up to four pumps are controlled by a single variable-frequency drive.
Sensorless vector control allows the drive to control the speed and torque of a motor precisely, enabling the CFWO8 to be used on demanding duties such as extruders, conveyors and rewinders, for example.
Designed for operation in the range 0.25kW to 15kW, the CFW-08 is said to be easy to configure, install and operate. It integrates a host of special features that make the job of the user that much easier. These include S acceleration and deceleration ramps, local remote control, DC braking, torque boost, motor slip compensation, JOG, ride-through, multi-speed (up to eight speeds), maximum and minimum adjustable speeds, two skip frequencies, PID regulator, flying start, and built-in Devicenet, Modbus RTU and Canopen fieldbus protocols, with Profibus DP as an option.
In addition to the standard CFW-08, WEG is introducing an IP56-rated version, the CFW-08 Wash. This is designed for applications in food, beverage, chemical and water treatment industries requiring a higher degree of protection against the ingress of water and dust.
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