Shaft voltage: How to prevent wear on your powertrain


Danger to your assets!

How to prevent wear on your powertrain caused by shaft voltage using a sound grounding concept.

Are you familiar with this? Unusual noises in bearings or gears occur and an unspecific trouble shooting process begins because the root cause of the problem can be very diverse. Typical causes are wear and tear or imbalances which can both lead to vibrations. Another factor contributing to noise development and wear which is often neglected is the so-called shaft voltage. With our expertise as a maintenance provider, we would like to introduce you to this phenomenon, methods of evaluation and effective countermeasures.

What is shaft voltage and why does it occur?

In electrical processes, like in electric power trains, there is always a physical interaction between voltage, the resulting amperage and consequently, the resulting magnetic and static fields. There’s also a negative side-effect that occurs: the so-called bearing current.

Static charges occur on conveyor belts, plastic films, paper and foil webs – these lead to high-frequency voltages on the surface. Unlike the conventional ground currents, these will not be diverted through the grounding cable cross-section, but through the surface of the grounding cable.

To safeguard your system, you need fine grounding cable for a sound grounding concept. It is also important how careful the ends of the grounding cables are connected to your machine components. After changing the motor, the cable’s coloured insulation is often not properly removed, so that the shaft voltage cannot be correctly diverted even though the right cable was chosen.

In case there is a change in processing, e.g. when taking up the paper, the shaft voltage is not diverted through the paper, but discharged through the powertrain. Voltage peaks of up to 400 volt are not uncommon. Due to bearing tolerances and high voltage on the powertrain, sparks occur which in turn lead to material damage, causing premature wear of components and costly repair and maintenance measures. A sound grounding concept and choosing the right materials for grounding is a good method to prevent those costs. A shaft-voltage test is necessary to choose the right grounding concept and assess the existing shaft voltage in your systems.