Industrial Engineer · phase 13 of 16 · noun
Bearing Current
Unwanted current through motor bearings caused by common-mode voltage, shaft voltage, or grounding paths.
The Explain card
- Plain English
- Bearing current is electricity finding a path through the motor's bearings. Common mode voltage charges the shaft, and when the voltage across the oil film exceeds what it can hold, it discharges through the balls and races.
- Example
- A motor behind a drive fails at eighteen months with bearings that look frosted or fluted. There was nothing mechanically wrong with them.
- Why it matters
- It is one of the most common causes of premature motor failure on drives, and it is invisible until the bearing is opened. Shaft grounding rings, insulated bearings, proper cable shielding and bonding are the defences.
- Hook
- Tiny sparks inside the bearing, thousands of times a second.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During VFD commissioning, the technician checked for bearing current by measuring shaft voltage and inspecting the shaft-grounding ring.
Why these words
- bearing Old English beran, to carry or support specifies the motor component under examination
- current Latin currere, to run, through Old French corant serves as the head noun naming the electrical quantity
Where it came from
- Origin
- English technical compound formed from bearing and current
- Entered the language
- 20th century
- What changed
- Bearing developed from the idea of carrying a load to a mechanical support, while current developed from running or flowing to an electrical quantity.
How it is spelled
- Pattern
- Bearing keeps the base bear before the suffix -ing.
- Pattern
- Current keeps the double r found throughout its word family.
Spelled like
- bearer
- wearing
- currency
- recurrent
Broken into chunks
-
bear
- bearer
- bearable
-
ing
- grounding
- commissioning
-
curr
- currency
- recurrent
-
ent
- persistent
- dependent
What it sits beside
Same subject
- shaft voltage
- common-mode voltage
- shaft-grounding ring
- insulated bearing
- variable frequency drive
Same shape
- leakage current
- charging current
- fault current
motor bearing protection methods
- insulated bearing
- shaft-grounding ring
VFD-related electrical measurements
- shaft voltage
- common-mode voltage
Where it sits in the deck
Phase 13: VFD Power Quality, Wiring, and Motor Protection
Harmonics, reflected waves, shielded cable and bearing currents: the side effects a drive inflicts on everything around it.
