Using Dynamic Electric Motor Monitoring to Identify Mechanical Issues

Dynamic electric motor testing is often called on-line testing because it requires the motor to be running and generally assumes the motor is in its natural environment. Dynamic testing involves the connection of voltage probes and current transformers. Connecting dynamic test equipment is safe, quick and non-intrusive. Data is acquired and results are displayed in a summary format. The collected data is compared to the user-entered nameplate information and is presented in a pass/fail format with both current test data and trending logs displayed after each successive test.

The Need for Motor Testing

Every reliability technician knows that costs associated with motor failures can be devastating to any business operation. Finding that a motor is operating with conditions that create excessive heat or stress is a guide to the technician to make changes in the motor’s operation and to monitor its insulation. Knowing that a motor is in imminent danger of failing provides the technician with time to schedule repairs at his convenience rather than having the motor dictate to him due to a catastrophic failure. Reducing unscheduled downtime while increasing efficiency and profitability are common goals of all reliability technicians. Dynamic motor testing and monitoring is a relatively new concept aiding and advancing the capabilities of those responsible for the safe and continuous operation of electric motors and related equipment.

What Dynamic Testing Tells You

A motor is one part of a complete system that includes incoming power quality, the motor and the driven load. Many motor problems are created by poor incoming power quality, and many more problems can be attributed to the load and load-related issues.
State-of-the-art dynamic motor test equipment is capable of separating electrical issues from mechanical issues as well as defining power-related problem areas. Good test equipment will provide an enormous amount of information regarding the incoming power, including voltage levels, imbalances and harmonic content. A small amount of voltage imbalance will result in a much larger amount of current imbalance and increase losses within the motor. Harmonic distortion also results in wasted energy causing overheating due mainly to non-sinusoidal sine waves. These issues directly affect a motor’s performance and its ability to handle its load. Overall, poor power quality manifests itself as higher heat within the stator and rotor, reducing efficiency and eventually resulting in premature motor failures. Monitoring power quality and making necessary adjustments are essential in maintaining motor longevity.

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