Introduction: The Silent Killer of Bearings
Have you ever encountered repeated, unexplained bearing failures in your electric motors? Despite proper lubrication, alignment, and load conditions, the bearings wear out prematurely?
The culprit may not be mechanical — it could be an invisible electrical threat: shaft current.
This often-overlooked phenomenon can cause catastrophic bearing damage, leading to unplanned downtime, costly repairs, and reduced motor lifespan. Understanding how shaft current forms — and how to stop it — is essential for maintaining reliable motor operation.
What Is Shaft Current?
Shaft current is an unwanted electrical current that flows through the motor shaft and its bearings. It occurs when a voltage difference — known as shaft voltage — builds up on the rotating shaft.
When this voltage finds a path to ground — typically through the bearings — current flows through them, causing progressive and often irreversible damage.
How Is Shaft Voltage Generated?
Several factors can induce voltage on a motor’s shaft. The most common sources include:
