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Magnetic Torque Transfer
Drive eliminates mechanical wear by transferring torque through air gap
Al Presher, Contributing Editor -- Design News, October 13, 2009
Flux Drive technology uses induction motor theory and improvements in permanent magnets to create a magnetic torque transfer system for its new soft-start couplings and adjustable speed drives (ASD). Drawing on high-performance permanent magnets, this new option for soft-start couplings combines high efficiency and long life.
The flexible soft-start coupling's rotating magnetic assembly and input rotor provide an almost one-to-one transfer of power from the motor to the load. By relying on the coupling's air gap, a load can slip with respect to the motor, while still accelerating to full motor speed without spiking motor current. Philip Corbin III, founder and CEO of Flux Drive says that eliminating contacting mechanical parts results in significantly reduced vibration and no parts to wear out or replace.
"The soft-start coupling transfers torque magnetically through an air gap," Corbin says. "If there is an overload, applications are typically limited to 130 or 140 percent of the torque that the system would normally be able to transmit from the input to output shaft. The coupling becomes a protective, torque limiting device for the system."
The Flux Drive adjustable speed drive combines the soft-start coupling with the ability to adjust the axial engagement between the rotating magnetic assembly and input rotor. The magnetic ASD provides variable speeds by relying on permanent magnets and a design that allows the drive to transfer torque across an air gap instead of through mechanical parts.
"What makes Flux Drive unique is a magnetic circuit that closely follows motor technology in its modeling and development," says Corbin. "The design uses an inductive rotor which fits inside a magnetic can, and creates an always on, dc flux field. Once the rotor is placed into the array and flux field, there is incredibly high magnetic strength within the can, and interfacing to the rotor."
"When we run at full torque, we are designing around a 1½ to 2 percent slip for an 1,800 rpm application," Corbin says. "That's 24 to 30 rpm of slip speed between the input shaft in the motor and the output shaft mounted to a pump or blower." He claims that eddy current offerings have the same available torque as the Flux Drive product, but slip is 4-5 percent at full torque and power.
Flux Drive was awarded a patent in 2007 based on the inductive circuit. The key to the patent is the design's ability to utilize an organized array of magnets and an organized rotor to create an interface that induces flux and torque across the air gap.
Corbin compares the adjustable speed product to frequency drives which create disturbances on the ac power lines. Because the Flux Drive does not create any power line disturbances, it is ideal for applications where sensitive equipment could be affected by operation of a frequency drive.
A Flux Drive ASD installed on a motor/pump application allows the motor to run at its best efficiency point. The drive transfers torque across an air gap instead of through touching parts.
