Is the shielding on my current leads affecting my power measurements?

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Shielded drive-to-motor cabling is often used to minimize emissions of high frequency signals during power system testing. When this full-cable shielding is used, there can be parasitic currents returned to the AC drive through the cable shields, especially if the shielding is grounded at both ends of the cable (motor and inverter). To avoid letting this return affect your current measurements, it is necessary to break the shielding at the point of the current transducer so that the parasitic currents return outside the transducer aperture. The effects of this parasitic current can be seen as lower current measurements made by the CT and power analyzer, which can lead to inconsistent and unexpected current and efficiency readings for the motor and drive system.

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