Is It Possible to Check if Your Motors are Defect Free?

YES, it’s possible to check if the windings, insulation, rotor, stator, power supply, and connectors are free of defects.


A study conducted in 1985 by the Electric Power Research Institute (EPRI) in association with GE found that motors failed 41% due to bearings failures, but 47% of the time due to rotor and stator failures.

1985 EPRI/GE Study EL 4263-286 Volume 1 Project 17

You Don’t Have to be Part of the Statistics

Motor Circuit Analysis (MCA) test the motor when it is off-line, thus making it Safe and a Convenient method to test you motor’s health. Motor Circuit Analysis (MCA) is a de-engergised test method to access the health of the motors in your plant.

This method can be initiated from the Motor Control Centre (MCC) or directly at the motor, itself. The advantages of testing from the Motor Control Centre (MCC) is that the entire electrical portion of the motor system, including the Connections and Cables between the test point and the motor is evaluated.

How Does It Work

The electrical portion of the 3 phase motor system is made up of the basic motor circuit, which is nothing more than 3 simple RCl circuits (resistive, capacitive, inductive). Each basic circuit represents one phase of the three-phase motor system. Each phase of the motor system is identical, each basic circuit should respond the same way to an applied signal.

Diagnostic with regards to failures can start as indicated in the below image, between turns in the same coil, between coils in the same phase, and phase to phase. Motor Circuit Analysis provides a Complete view of the motor in just minutes.

Typical Test Sequence

Traditional Megohmmeter – IS NOT ENOUGH

Megohmmeter insulation testing will only detect faults to ground. Only a portion of the Motor electrical winding failure begin as ground faults, they will go undetected using this method, alone. Moreover surge testing requires the application of high voltages, which can be destructive when testing a motor, making it unsuitable for troubleshooting and true Predictive Maintenance Testing.

Megohmmeter Vs. Digital Multimeter

Therefore,  when  testing  Three-phase  equipment  such  as  motorsgenerators,  or  transformers,  the  response  of  each  phase  is  compared  to  the  other  two.

Phase  resistance  is  evaluated  to  determine  connection  issues;  Inductance  is  evaluated  for  possible  rotor  problems;  Impedance  and  inductance  matching  are  used  to  detect  contamination  or  over-heating  of  the  windings;  Insulation  to  ground  tests  detect  conductor  to  ground  issues

Motor Circuit Analysis Is the Way Forward


Typical applications where Motor Circuit Analysis is most effective

  • AC/DC Motors
  • AC/DC Traction Motors
  • Generators/Alternators
  • Machine Tool Motors
  • Servo Motors
  • Control Transformers
  • Transmissions & Distributions Transformers

Motor Circuit should also be used for;

  • For Commissioning purposes
  • Troubleshooting
  • And, Reliability Testing

CIS Industrial Services – Expertise You Can Count On!!!

CIS Industrial Services has appointed Dickey Kruger during February, 2020.

Dickey Kruger has 17 years of experience in the field of Motor Circuit Analysis. He has a vast experience in the Mining Sector, diagnosing electrical drives, from a simple Motor driving a conveyor belt to a more complex machines such as, Continuous Miner for the under ground mining operations.

Should you wish to measure your Electrical drives in your plant effectively, please do not hesitate to get in touch with CIS Industrial Services to make use of this wealth of experience, assisting you, making sure your drive’s runs effectively as they were designed too.

About CIS Industrial Services.

CIS Industrial Services are a leader in the supply of advance Oil Condition Monitoring technologies, Vibration Monitoring technologies, Motor Circuit Analysis (MCA), Products, System and Services.

The products we represent are trusted by the world’s leading industrial and commercial companies to monitor Vibration, and Oil, helping to optimise equipment productivity, reduce operating cost, thereby remaining competitive in a global economy.

Should you wish to learn more about our Products and Services, please do not hesitate to contact Lourens Janse Van Rensburg via email: or alternatively via phone: +27 (0) 79 512 8027