Bridge cuts drive harmonics

Mitsubishi Electric has released a high-current active bridge unit for its variable speed drive ranges, which is designed to eliminate unwanted harmonics caused by traditional drive controllers.

Mitsubishi Electric has released a high-current (HC) active bridge unit for its variable speed drive (VSD) ranges, which is designed to eliminate unwanted harmonics caused by traditional drive controllers.

The HC active bridge unit effectively replaces the usual six input diodes normally used on a VSD, and replaces them with six power transistors, which switch in phase with the supply voltage sinewave - effectively eliminating harmonic noise.

The typical harmonic distortion total from a standard VSD across all the harmonic orders is about 30%.

The performance improvement of the new HC active bridge unit gives a VSD a harmonic distortion of 1% in driving mode and down to 0.7% in regenerative mode, dramatically reducing unwanted harmonics and increasing energy efficiency.

A bonus in utilising this technology, is that it removes harmonics yet can flow energy equally well from the drive back onto the incoming supply, thus conserving even more energy, especially on overhauling loads.

The development of this new harmonic control unit is a direct response by Mitsubishi Electric to the impact of the recent G5/4 initiative to provide an effective solution to unwanted harmonics.

The arrival of this new technology enables Mitsubishi Electric's VSDs to replace traditional four-quadrant controllers, in many applications, removing the need to use DC drives from most motor control.

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