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Add filters to frequency inverter to eliminate harmful

The high frequency edges of switched waveforms can cause capacitively coupled currents to flow from windings to frame, returning through the bearings, and these can accelerate corrosion in the bearings, causing early failure. Small filters on the motor leads allowing these currents to return locally to ground will avoid this.

The best way, though, is to use filters which can eliminate sharp transitions and leave only (like +/-10% ripple) fundamental frequency (motor's RPM at given point) of the frequency inverter. The problem is that such filters are considered to be big and expensive. It is true if the switching frequency is below 10kHz which is used in most of motor drives. However if somebody can handle 40 - 50kHz of the switching frequency the filter's size shrinks dramatically and it is not too expensive anymore. Again, the problem is in ability to handle 100 (or so) kWs and 50kHz together.

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