When it comes to motor testing, the most important thing to remember is that it should not be done only when a motor is acting up but rather as part of a regular preventive maintenance schedule. Conducting even basic motor testing goes a long way in saving precious time, money, and manpower. Over the years, motor data collection and testing techniques have evolved significantly, making it easier to uncover and troubleshoot motor problems. Currently, there are two types of motor testing methods: energised and de-energised.
Energised testing is the more common and preferable testing method as it takes place while the motor is running under simulated load, which enables accurate identification of issues that may occur during normal operations. Moreover, testing while the motor is on means you can perform dynamic testing that is more suited to detecting temperature, balance, and distortion problems. In contrast, de-energised testing is a safer method wherein the motor is run through its paces by checking for wire damage, insulation resistance, and current leakage while in an offline state.
Regardless of which of the two categories they fall into, modern motor tests leverage computer-guided tools to measure the motor’s integrity and monitor the trends and baselines in its inner workings. Operators now have access to various diagnostic tools to troubleshoot motor issues and even perform electric motor rewinds. Without further ado, the following are some motor testing tools and techniques organisations need to add to their preventative maintenance toolbox.
1. Surge test
Surge testing is the go-to method for reliably detecting motor burnout and predicting potential motor failure. Performing the test involves using a testing machine to apply a safe level of surge or voltage pulse to each set of windings to isolate their performance. Through this process, users can then detect if there is insulation failure or shorted motor conductor turns. Overall, surge testing is the most efficient way to uncover turn insulation weaknesses, including phase-to-phase and coil-to-coil insulation.
2. High potential/Voltage test
Often shortened to just the Hipot test, this method is a minute-long test that takes place at a specified voltage that goes beyond the motor’s peak to lead operating voltage to ensure that the motor insulation is free of defects and functioning as expected. Detecting issues with the insulation is key to preventing the motor from encountering a short circuit or power leakage that may lead to damage or, worse, complete motor failure. Some common issues that a Hipot test can reveal include stray wires, damaged insulation, contaminants in the conductors, and more.
4. Megohmmeter test
The megohmmeter test provides reliable periodic testing of the overall performance of a motor’s insulation by applying high voltage for a certain amount of time and measuring for leakage current through the insulation. The information gathered from this process can then be graphed to evaluate the state of the insulation over time and stay on top of the motor’s maintenance needs.
4. Digital multimeter
A digital multimeter combines the testing capabilities of many single-task metres, resulting in a comprehensive tool that can measure amps, ohms, and volts. Multimeters fall into a handful of categories ranging from general purpose to advanced, making it tricky to find the one you need. From a feature perspective, the most important factors to look for in a digital multimeter are:
- AC and DC voltage.
- The ability to measure current resistance and continuity.
- A certified safety rating.
5. Power quality analyser
A power quality analyser is essentially an improved digital multimeter with the added feature of assessing power quality, simplifying tracing harmonic distortion issues and voltage anomalies that may develop over time. Many of these events typically fly under the radar since they come and go in very quickly, making them hard to define and detect. But with the help of a power quality analyser and its event capture and high-speed wave shape, operators can more easily identify these disturbances.
Conclusion
When a motor encounters an issue working, determining the cause can be challenging without the help of a technician. However, by knowing the basic motor testing methods and having the necessary tools to perform them, you can detect and diagnose motor problems more confidently. Should the issue be beyond what you can address in-house, working with an electrical and mechanical engineering services provider is the best option to get the timely electric motor overhauling or rewinding you need.
