Variable-speed control alternative is ‘magnetic’

Seattle, Wa . —A sophisticated, magnetic “coupling” placed between a motor and its driven load enables variable-speed control of ac motors up to 600 hp at 460 V—as well as medium-voltage (4,300 V) motors. The device is not another version of eddy-current control. MagnaDrive Coupling consists of a copper conductor assembly connected to the motor shaft and a precision rotor assembly (containing rare-earth neodymium-iron-boron magnets) connected to the load shaft.

Relative motion between the Nd-Fe-B magnets and copper conductors develops a magnetic field that transmits torque through the air gap between the input and output members—although they are not mechanically connected. A linear actuator that responds to 4-20 mA process signals controls torque magnitude by adjusting air gap width.

MagnaDrive Coupling offers several benefits, such as “soft” start/stop control, elimination of harmonics and coupling-induced vibrations, and insensitivity to input voltage/power quality. Ownership and maintenance costs are said to be lower than a comparable variable-frequency drive. Initial application successes have been in speed control of pumps, fans, and lowers. www.magnadrive.com .

MagnaDrive Corp. Circle 415

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