Motor Circuit Analysis

MTI’s Motor Circuit Analysis (MCA) provides a complete analysis of your motor circuits.  Utilizing state-of-the-art Motor Circuit Analysis technology on an on-going basis, MTI’s staff can obtain a detailed look of your motors electrical components to identify problems that need to be addressed before failure occurs.

MTI utilizes the MCEmax™ to conduct extensive Motor Circuit Evaluation. With the MCEmax™ there is no need to break motor connections to initially test the entire motor circuit. On-line or off-line, the MCEmax™ tester is designed for convenient field use. Unlike more invasive methods, the low voltage and minimum current test signals ensure no damage to motor or circuit.

On-line Emax Testing Capabilities

MTI’s on-line motor circuit evaluations are non-destructive. On-Line Emax™  Testing includes:

  • Current Signature Analysis – Performed through a combination of frequency versus dB amplitude spectrums (graphs) and software automation to identify rotor bar defects and or static or dynamic eccentricity.
  • Start-Up In-Rush Tests (when possible) – Performed by recording graphically the amperage versus time for the motor to get to normal operating speed and load. Changes in start-up characteristics can be attributed to rotor or stator faults. Also, like motors / equipment can be compared for evaluating which is in better condition.
  • Power Analysis – (480 volt systems ONLY or higher volt systems if current transformers and potential transformers are installed and available on all three phases). Provides invaluable insight into incoming power quality, power circuit condition, stator health, and motor efficiency.

Off-Line MCE Testing Capabilities

MTI’s off-line motor circuit evaluations are non-destructive. Off-Line MCE™  Testing includes:

  • Resistance to Ground (RTG) – Temperature corrected to 40 degrees C at 5,000 volts DC on 4160 volt motors, 2,500 volts DC on 2400 volt motors, and 500 volts DC on 480 volt motors. RTG looks at the insulation system integrity.
  • Polarization Index – Graphed 10 minute RTG test of the motors cable and winding insulation resistance to ground leakage potential. The graph will indicate if there are momentary RTG value decreases over the 10 minutes which could indicate problems that not evident using non-graphical analog or digital testers.
  • Capacitance to Ground (CTG) – Determines the cleanliness of the stator windings-conductive material buildup. CTG is correlated with RTG to determine when a motor should be sent out for a clean dip and bake.
  • Resistance Phase to Phase (RP-P) – Detects high resistance connections which can cause overheating.
  • Inductance Phase to Phase (IP-P) – Examines the stator and the rotor for turn to turn or phase to phase shorting, broken rotor bars or end rings, eccentricity and casting voids.
  • Average Inductance – Used to compare the same or like motors for possible problems such as a motor not being re-wound correctly.

Related PdM Technologies: Vibration Analysis and Infrared Thermography.


What types of motors or motor circuits can be analyzed?

AC Induction, DC, AC Synchronous, Wound Rotor, Servo, and VFD motor circuits can all be tested.

What problems can Motor Circuit Analysis uncover?

The Offline motor circuit analysis can detect problems and/or provide trending information on Motor Leads, Stators, Rotors, Fields, Armatures, Brushes, Resistor Banks, Coils, Contactors, Power System, etc.


Can a VFD (Variable Frequency Drive) powered unit be tested?

Yes, on-line tests including power quality tests before and after the VFD can be performed to evaluate VFD problems that may be present.

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