Disturbance of signals: voltage edges on current signals

The current signals are recorded at 2 MS/s with 600 kHz filtering (8th order). Due to the impedance of the coils current slopes are of limited steepness. The behavior below (spikes) cannot be explained by the expected electrical behavior.

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These spikes in the current, in a moment of steep voltage edges, could have been caused by mutual interference between power lines and measuring lines. Relocating the cables (unwinding coils and laying excess length in a meandering pattern, relocating cables locally when signal cables were close to high-current cables) led to the disappearance of the “spikes.”

Please always consider signal patterns in your measurements from this perspective—it is possible to eliminate such influences, and the success can be verified directly.

How to improve signal quality:

• guide power lines from inverter to motor distant from signal lines
• organize cable overlength in meander instead of coil
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