Two Minute Tips  

Space Heaters

Noah Bethel | Vice President-Product Development, PdMA Corporation

Depending on the environment and criticality of your electric motor, space heaters should be strongly considered if you want to ensure maximum reliability and expected motor life. When a motor is secured (de-energized) there is an initial increase in temperature due to the loss of cooling air. However, very quickly after shutdown, the temperature of the motor windings will start to drop. Once the temperature falls below the dew point, air moisture will condensate on the windings and machined surfaces creating a conductive path for current to ground. This drop in resistance to ground due to the surface moisture contamination can cause a low state of reliability for the next startup and increase the chance of a failure. When selecting a space heater, a simple calculation can give you a ballpark estimate for power requirements to remain above the dew point.

H = DL/35


H = Heater size in kW

D = Diameter in Feet

L = Length in Feet (between end bell centers)

To see the results of excessive moisture on a 2000HP electric motor visit the PdMA YouTube Channel at:

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About the Author

Noah Bethel Vice President-Product Development, PdMA Corporation

Noah has over twenty-five years of broad operations and electrical systems maintenance experience in industrial, commercial, and military settings ranging from nuclear submarines to world class amusement parks. His experience includes high and low voltage, AC and DC, power generation, power distribution, motors, and motor controllers. Noah is currently in charge of product development for new and existing PdM technology at PdMA Corporation.

Noah is a graduate of the University of the State of New York and the Naval Nuclear Power School and Training Unit. He is a Certified Maintenance Reliability Professional, with field experience in motor circuit analysis, current signature, power analysis, thermography, vibration analysis, oil analysis and ultrasonic testing.