Summary
Various faults can be detected with on-line methods, but with unsteady load the diagnosis might be inconclusive. Known off-line methods can be of limited sensitivity or requiring shaft rotation. DC resistive imbalance (DC R) test is prescribed by EASA AR100, but true DC R of an assembled motor is not measurable with ordinary short-time techniques. This new improved off-line method can be applied on assembled machine, to provide alternative detection of the total electromagnetic imbalance (through the parameter RE-M): air gap eccentricity, broken rotor bars, connection issues, etc. It utilises long decay time (>> 1 s) of the rotor RL circuit. The true resistive imbalance (Rtrue DC) is measured and used for decomposition of the electromagnetic trajectory, hence “dual imbalance”. Motors ranging from 1.5 kW to 90 kW were tested with simulated faults (collapsed bearings and drilled rotor bars), and the RE-M % parameter was found to be proportional to the total amount of electromagnetic asymmetry, on all tested motors.
Read more Read lessLimited tests were applied to much larger HV motors (630 kW, 3 MW, rated up to 13.8 kV) and the results suggest that the method is applicable to any size.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | A1_11536_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | United Kingdom |
| Study committees | |
| File size | 983 KB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
PETSOV Dimitar - Megger Instruments United Kingdom; ZUREK Stan - Megger Instruments United Kingdom; JONES Jeff - Megger Instruments United Kingdom; RIVRON Tony - Megger Instruments United Kingdom
Keywords
motors, generators, rotating machines, resistive imbalance, electromagnetic imbalance, air gap eccentricity, open rotor bars, broken rotor bars, winding resistance, collapsed bearings
