Improving variable speed drive costs

02 October 2008

A cost-saving solution to specification problems for AC induction motors running at slow speeds under frequency converter / variable speed drive control has been developed by Weg Electric Motors. Weg’s patented Optimal Flux Technology (OFT) solution eliminates the cost and size penalties of some manufacturers and enables motors to run cooler over the entire speed range.

CFW-11 Variable Frequency Converter

The Weg NEMA High, Premium or EFF1 AC induction motor and the Optimal Flux option with the CFW-09 Variable Frequency Converter combination, costs around 10% less than competing inverter class drive solutions. The Optimal Flux CFW-09 or CFW-11 Variable Frequency Converter has a self-calibration setup for the most efficient operation when starting to drive the electric motor. Weg can offer a three year extended warranty, with less maintenance costs and down time.

Typical applications include positive displacement pumps, conveyor belts and compressors, and motors range from 3kW and 110kW in power.

Andy Glover, Product Manager LV Machines at Weg commented: “Optimal Flux Technology is the result of Weg’s developments in frequency converter programming architecture which ensures the drive adjusts the flux of the motor to ensure minimum losses at every speed.

“The specific advantages of the Optimal Flux solution are also demonstrated in the new Weg CFW-11 drive. As result, a Weg 20HP NEMA Premium runs 22% cooler using the Optimal Flux solution when compared to constant flux, for example.

“This contrasts with conventional drives where the flux is kept constant, resulting in temperature rises at low running speeds with constant toque which can significantly reduce the life of the coil insulation, halving the motor lifetime for a 10°C rise. To reduce this effect, conventional solutions include extra external fans for cooling or oversize the motor so as to minimise the extra heat load, but always resulting in more expensive package units.”

Conventional solutions can therefore take up extra space, may be overpriced and not energy efficient, or else run the risk of early breakdown, high maintenance costs and unexpected downtime. With Optimal Flux CFW-09 or 11 drives combined with Weg Energy Efficient motors, the occurrence of such problems is minimised and the improved environmental efficiency and reduced operating costs are able to benefit every business.