Two Minute Tips  

What is the Rotor Influence Check (RIC)?

Noah Bethel | Vice President-Product Development, PdMA Corporation

Six independent methods of rotor evaluation can be used from the MCEMAX technology to analyze the condition of a squirrel cage AC induction motor: Pole-pass frequency (Fp) sidebands around line frequency, 5th harmonic, demodulated Fp frequency, Rotor Influence Check (RIC), In/Rush-Start/Up, and average inductance. Over the next six tips we will discuss each of these methods in detail and provide examples.

Cracked or broken rotor bars

The Rotor Influence Check (RIC) is a test performed with the motor de-energized. High resistance, cracked, or broken rotor bars and end rings will cause a non-symmetric reflected impedance onto the stator windings resulting in elevated inductance levels for the stator phase located over the rotor fault. Rotating the rotor in calculated increments and retesting the inductance will present a clear image of the residual flux and reflected impedance coming from the rotor. Variations of inductance indicative of rotor defects will affect all phases of the stator similarly allowing you to isolate the anomaly to the rotor.

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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.