GPD Multiplexer for HVAC and Pump Applications
Operation
The GPD Multiplexer utilizes one GPD 506 VFD, with horsepower rated for the largest motor, and sequentially controls all the motors to achieve infinitely variable response to system demand. MagneTek has developed the unique and reliable method of transferring motors back and forth between the VFD and the power line as demand increases or decreases. For example, as demand increases, the GPD 506 ramps up a motor until it reaches full speed, at which time the motor is switched to the line to run full speed and the GPD 506 operates the next motor at variable speed.
Control of the system is accomplished by the Multiplexer Control Unit (MCU), based upon a single demand input signal (0-10vdc or 4-20mA) from the customer. The MCU has an on-board PID loop for set point control based upon a system output sensor (e.g. flow rate, temperature, pressure, tank level, etc.). The sensor signal is fed to the MCU, which compares it to the customer defined setpoint and corrects system output accordingly. The setpoint can be manually defined on the MCU control console or automatically defined from another control system.
Magnetek Drives & Systems, 16555 West Ryerson Road, New Berlin, WI 53151. Tel: 262-782-0200; Fax: 262-782-3418.