According to the company, motor installers and design engineers can deal more effectively with high frequency (hf) common-mode currents caused by variable-frequency drives, using the non-contact current probes.

They use Rogowski technology, allowing engineers to assess the magnitude of the threat posed by hf common-mode currents, that can damage motor bearings and interfere with nearby electrical equipment. The current measurements can help determine suitable corrective action, such as fitting brushes, insulated bearings, or choke coils, and, with further measurements, assess the effectiveness of the chosen remedy.

The screened coils have immunity to  voltage disturbances and a low frequency (-3dB) bandwidth that attenuates unwanted 50/60Hz  magnetic fields while maximising the SNR of the measurement of the high frequency common mode currents.  Available in coil sizes from 300 to 1000mm (longer if required) for use with a range of motor shafts. Even with a coil circumference of 1,000mm the CMC probes can achieve a high frequency (-3dB) above 10MHz.

The probes are available in three sensitivity grades for measuring bearing currents up to 37.5, 75 or 150A peak. The peak detected current corresponds to a maximum output voltage of  ±7.5V when connected to an oscilloscope input via the BNC output provided.

Visit PEM at PCIM 2016 – Hall 7 – 122