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Ferrite magnet motors are 3% more efficient than Nema Premium

05 February, 2014

The Californian motor manufacturer NovaTorque has announced 7.5hp (5.6kW) and 10hp (7.45kW) versions of its electronically commutated permanent magnet motors, which it claims are 3% more efficient than Nema Premium induction motors.

The PremiumPlus+ motors use low-cost ferrite magnets in a novel flux-focusing design that is claimed to deliver the efficiencies of rare-earth permanent magnet motors at a price that is competitive with induction motors.

According to Scott Johnson, NovaTorque’s vice-president of sales, the new motors, when driven by variable frequency drives (VFDs), achieve motor-only rated-point efficiencies of more 94% – 3% higher than those of Nema Premium motors. They also exceed the proposed IE4 efficiency ratings.

“That advantage grows under partial load,” he adds, “as is the case in variable-speed fan applications, with typical efficiency improvements ranging from 5–15%. In a high duty-cycle 10hp fan application, in an average cost-of-power area, annual energy cost savings can exceed $300. The advantage is even more dramatic when compared to the current installed base of induction motors, where efficiency improvements of 20% or more are achievable.”

Novatorque’s patented flux-focusing stator and rotor hub geometry allows its motors to deliver this performance using ferrite magnets rather than expensive rare-earth types.

The efficiency curve for a high-speed 10hp NovaTorque motor in a fan application (blue), compared to the Nema Premium (green) and Epact (red) specifications

“The cost of rare-earth (neodymium) magnet material – the basis of most conventional permanent magnet motors – has risen erratically over the last several years,” points out Jaffer Hussain, NovaTorque’s vice-president of marketing and product management. “Further, supply of rare-earth magnets is increasingly uncertain.

“The ability to use ferrite magnets allows NovaTorque to price its motors comparable to induction motors,” he continues. “This means OEMs and HVAC systems builders can now economically deliver superior permanent-magnet motor efficiency with modest first-cost impact and a rapid payback.”

The NovaTorque motors are available in high-torque versions (with a top speed of 2,700 rpm) or in high-speed versions (with a top speed of 3,600 rpm). They have standard Nema frame sizes and mounting dimensions, allowing easy replacement of AC induction motors. The motors are compatible with most VFDs.

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