Motor Current Signature Analysis

Motor Current Signature Analysis (MCSA) is a diagnostic technique which is used to analyse Motors, Transformers, Generators, Alternators, Distribution and other Electric Equipment. It has proven to be a highly valuable predictive maintenance tool. Although it is a relatively young, rarely utilized technology, it is rapidly gaining acceptance in industry today. Mechanical faults related to belts, couplers, alignment and more, are easily found through the use of a demodulated current spectrum.

ROKADE Group provides industry with the most advanced predictive maintenance testing and troubleshooting tools for AC and DC Motors, Coils, windings, Transformers, Generators, etc. to a wide range of industries worldwide. We have a full line of testing instruments, software, accessories and training programs, to meet the varied needs of the Clients.

We perform advanced non-destructive motor testing and analysis for both de-energized motor circuit analysis and energized electrical signature and power analysis, by deploying our well trained technical personnel to ensure improved productivity, reduced downtime and a rapid return on investment.

Motor Current Signature Analysis

Scope of Motor Current Signature Analysis

The following Fault Zones can be identified in this method to effectively report on the condition of Motors

Power Analysis

Stator Fault

Rotor Fault

Air Gap

Power Analysis

By analyzing the power quality and power circuit condition, the health of the motor can be effectively determined. Non-linear switching loads from variable Frequency Drives, computers and fluorescent lighting cause harmonic distortion in the system, resulting in excessive current and overheating. The additional current would lead to insulation failure of the windings.

The Power circuit refers to the incoming supply to the Motor Controller up to the motor windings. High resistance joints and contacts in this circuit are known to be the source of 46% of the faults which would reduce motor efficiency. This would cause problems like harmonics, voltage and current imbalance, resulting in reduced horsepower rating of the motor, to overheat the windings and eventually ending in insulation failure.

Stator faults are indicated by high impedance imbalance and rising negative sequence currents. Changes in startup current and time can be caused by stator or rotor faults. Hence it is important to record the various, parameters and trend the data to obtain useful information for diagnosis.

Stator Fault

By measuring the AC inductance per phase, any extreme imbalance in the readings would indicate turn-to-turn stator fault.

A phase-to-phase fault is usually indicated by high voltage imbalance between the phases.

Rotor Fault

A rotor bar defect is identified by comparing the Pole Pass Frequency side band to the line frequency (50Hz) and analyzing the data through an FFT Analyzer.

The difference in amplitude would normally be 50dB or greater. Broken rotor bars also cause skewed or erratic inductance patterns at the peak of the sinewave. 

Air Gap

If the air gap between the stator and rotor is not evenly distributed around the 360 degrees of the motor, uneven magnetic fields will produce magnetic imbalances to cause movement of the stator windings, resulting in winding failure, vibration and bearing failure. This static eccentricity is usually caused by shaft misalignment or the shaft sitting too low in the bearing.

This defect can be detected through variation in the peaks of the sinewave from the inductance measurements. Dynamic eccentricity happens when the rotor centre does not stay at one place but is allowed to move. This defect results in the movement of the inductance of all three phases up or down together. 

Detections Using Motor Current Signature Analysis

Stator faults.

Static and Dynamic air-gap irregularities.

Broken rotor bar or Cracked rotor end-rings.

Bearing and Gearbox failures.

Abnormal connection of the stator windings.

Bent Shaft (causing serious damage to stator core and windings).

Types of Motor Current Signature Analysis (MCSA)

Corrective

Run to failure.

Preventive

Pre-planned periodic motor replacement.

Predictive

Complete program that includes static and dynamic motor testing

Benefits of Thermography Services

Provides "Early Warning" information.

Determine root cause of problem.

It is Safe, Fast & Non-intrusive.

Ultimate goal: Save time & money.

Reduce unscheduled downtime by predicting imminent motor failures & identifying problem areas.

Applications

Rotor Bar testing.

Induction Motor Testing.

DC Motor Testing.

Synchronous Alternator Testing.

Industries served

Steel Plants

Power Plants

Cement Plants

Chemical Plants

Petrochemical Plants

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