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SKF signs deal for `harmonic-free` drive

01 June, 2001

SKF signs deal for `harmonic-free` drive

SKF is entering the inverter market with a deal to sell a Swedish-developed drive that is claimed not to produce any harmonics. One attraction of the drive for SKF is that it could solve the problem of bearing currents that can lead to premature failure of bearings on motors driven by conventional inverters.

The drive has been developed and built by NFO Drives. Instead of conventional PWM (pulse width modulation) switching, it uses a patented technique that it calls "sine switching". According to NFO managing director, Per Thomas, the inverter produces "a clean sine wave".

The drive also uses a patented control algorithm that, says Thomas, produces "almost servo performance".

Because the drive generates no harmonics, it does not need the usual precautions such as filters and screened cables. Although, the drive itself is slightly more expensive than standard drives, Thomas says that it is cheaper once the savings on filters and other measures are taken into account.

NFO began selling the drive under its own name in Scandinavia late last year, following five years of development. It is now producing versions up to 5.5kW, and plans to extend the range to 11kW by October, and eventually to 90kW. There are no immediate plans to sell the NFO drives in the UK.

SKF will initially sell its badged version of the NFO drive in Germany.

Until now, bearing companies have had to rely on techniques such as coatings to minimise the effects of bearing currents. According to Thomas, the NFO drive "eliminates the cause of the problems".

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