Motor Testing: Insulation Resistance and the Megohmmeter
Motors fail from insulation breakdown long before they fail outright. Testing insulation resistance and windings catches problems early, which is why motor testing is a core maintenance skill.
QUICK ANSWER
Motor testing checks the health of the windings and their insulation. A megohmmeter applies a high DC voltage to measure insulation resistance between windings and ground, catching insulation degradation before failure. A multimeter checks winding continuity and resistance balance. Together they reveal grounded, shorted, or open windings before a motor fails in service.
What the Tests Reveal
- Insulation resistance: a megohmmeter finds degrading insulation to ground.
- Winding resistance: a multimeter checks for opens and imbalance.
- Grounded winding: low insulation resistance signals trouble.
- Trend over time: falling readings predict failure.
Why Insulation Matters Most
Most motor failures start with insulation breaking down from heat, moisture, or contamination. A megohmmeter test catches that decline before the motor shorts to ground and fails. Trending the readings over time turns a single number into a prediction of remaining life.
Catch it before it fails
A planned motor replacement is cheap. An unplanned failure that stops a line is not. Testing turns a surprise into a scheduled task.
Motor testing supports motor control and industrial maintenance.
WE BUILD THIS IN VR — THE PRIME VR
We build motor testing into VR, so technicians safely megger windings, read insulation resistance, and check winding balance while the system models healthy and failing motors. Practicing the test and interpretation in immersion builds the predictive-maintenance skill that prevents downtime.
Book a discovery callFrequently Asked Questions
What does a megohmmeter test on a motor? +
A megohmmeter applies a high DC voltage to measure insulation resistance between the windings and ground. A low or falling reading indicates insulation degradation that can lead to a grounded winding and motor failure.
How is winding resistance checked? +
A multimeter measures the resistance of each winding to check for open windings and to compare the windings for balance. Significant imbalance suggests shorted turns or connection problems.
Why trend motor test readings over time? +
A single insulation reading is a snapshot, but trending readings over time reveals gradual decline, allowing a motor to be replaced on a planned schedule before it fails unexpectedly in service.
Train motor testing in VR
We build insulation testing into immersive, scored practice.