AEGIS® Bearing Protection - Why Shaft Grounding?


Measuring Shaft Voltages



Shaft Voltage Test Report

Shaft Voltage Test Report: Measuring the shaft voltage on VFD driven motors provides the user with valuable information to determine if there is a potential risk of bearing damage from electrical bearing discharges. Surveying and documenting shaft voltage readings and waveforms will assist in determining the appropriate mitigation or solution.

Note: The best time for shaft voltage measurements are during initial start-up in new or repaired motors operated by the VFD. Shaft voltage measurements should be incorporated into preventive and predictive maintenance programs and may be combined with vibration analysis, thermography or other services.

Report template available here.

Shaft Voltage Test Report

Recommended Testing Equipment: AEGIS® Shaft Voltage Tester™ 100 MHz Digital Oscilloscope with a 10:1 Shaft Voltage Probe™ kit. We recommend a minimum 100MHz bandwidth to accurately measure the high frequency transitions associated with bearing discharge and VFD waveforms.

Recommended Product: PN: AEGIS-OSC-9100MB-W2

  • Two 1X/10X probes, one with Shaft Voltage Probe™ SVP Tip attached
  • 1000V CAT III multimeter test leads
  • AEGIS® One-Touch™ instant image capture feature
  • USB flash drive for waveform recording
  • 5 hour+ rechargeable/replaceable Li battery
  • Carrying case

AEGIS® SVP Shaft Voltage Probe™
The AEGIS® SVP Shaft Voltage Probe tip attaches to an oscilloscope voltage probe to easily and accurately measure the voltage on a rotating shaft. The high density of conductive microfibers ensures continuous contact with the rotating shaft. The SVP-KIT-9100MB includes replacement tips, extender rods, a magnetic base/probe holder and AEGIS® Ring simulator.


Caution: Use appropriate safety procedures near rotating equipment.

Shaft Voltage Probe

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