Comparing Two Motor-Testing Approaches

Using the AT5 de-energized motor-testing instrument helped the in-house team test a motor in only 20 min. (includes moving between units).

Would in-house or third-party testing make more economic sense for an enormous motor fleet?

A large automotive manufacturing facility in the Midwest scheduled a planned shutdown in July 2018. In operation since the early 1980s, the plant spans more than 3 million sq. ft. and contains hundreds of motors and other essential equipment required for the site’s stamping, injection molding, welding, painting, and assembly processes.

The company’s engineering coordinator, Rich DaRe, a reliability professional for more than a decade, has taught predictive technologies for the vehicle manufacturer since 2014. This article involves an interesting opportunity that appeared on his radar.

THE OPPORTUNITY

During preparation for the planned, week-long shutdown, DaRe learned that an outside contractor had been hired to come on site to test motors. Having relied upon the hand-held, de-energerized ALL-TEST PRO 5 (AT5) motor-testing instrument from All-Test Pro LLC, Old Saybrook, CT (alltestpro.com), to perform in-house condition monitoring for the plant for the past several years, he was curious as to whether hiring a third-party would be more or less costly for the company than in-house motor testing.

DaRe reached out to his fellow in-house PdM technician, who agreed to help him test motors with the AT5 during the shutdown. The plan was to test 90% of the motors in the plant, with the outside contractors assigned a specified section and the in-house team testing their specified motors.

When the shutdown began, the motors to be tested were taken offline and disconnected from variable-frequency drives (VFDs) where required. DaRe and his partner tested each unit using the AT5, quickly collected the data for each, and then reconnected the VFDs. 

THE RESULTS

At the end of the week, DaRe reviewed the time it took for the outside contractor to perform motor testing and compared it to the time it took the in-house team to test 394 motors over a period of 128 hours. That time included disconnecting the motor leads (when required), taking the readings, re-wiring the motors back to the VFDs, and analyzing the AT5 reports. In comparison, it took 270 hours for the outside contractor to test 185 motors using its own proprietary PdM equipment (contractor hours include a plant escort). 

LESSONS LEARNED

Manufacturers need reliability programs. Catching motors before they fail saves headaches and significant money by avoiding unplanned shutdowns. The in-house team’s testing revealed two motors that needed to be replaced. The outside contractor discovered one. Being able to replace motors before they cause problems to the production line, and potentially other equipment, is critical for plant reliability. 

Testing in-house with the correct equipment can save time and, in turn, money. Using the AT5 de-energized motor-testing instrument helped the in-house team test a motor in only 20 min. (includes moving between units), whereas it took the third-party team an average of approximately 90 min./motor using their proprietary technology (includes time required to move between motors. Equipment size/weight meant a pulley system was sometimes needed).  

The AT5 motor-circuit analyzer offers a complete electric motor-health analysis in minutes, which makes it particularly efficient in planned-shutdown situations. “The real key here is the time it saves,” stated DaRe, who initially learned about the instruments from ALL-TEST Pro at an international maintenance conference.

Saving time is just one of the apparent benefits. “The AT5,” DaRe continued, “has been a superior approach for determining the condition of our
motors and will save us a lot of headaches in the long run. There is great benefit to developing in-house experts and having your own people make data-reinforced decisions.” EP

More About the Technology

The ALL-TEST PRO 5 can be used to test all types of motors, including induction, synchronous, AC, DC, brushless DC, servo, and wound rotors, as well as single-phase. The health of all motor components is evaluated, including, but not limited to, induction windings and rotors, DC field windings and armatures, and field and rotor coils in synchronous motors. Single and 3-phase transformers, pole and pad mounted, are also ideal candidates for evaluation with the portable, lightweight AT5.

With a memory-storage capacity for more than 650 tests, the AT5 has specific motor-trending data accessible at the touch of a button. Test results are easily uploaded to a computer and the MCA software provides expert diagnosis, trending, and a wide variety of printed or on-screen reports. With the ability to perform complete stator and rotor analysis, personnel can detect early faults in motors, transformers, and generators. Tests, which can be performed from distances of more than 1,000 ft., produce reports that show bad connections, winding and turn faults, air-gap issues, broken rotor bars, contamination, and ground faults. The auto diagnosis within the instrument provides an immediate status report on the equipment’s health, making route-based testing and trending extremely efficient. 

For more information on motor-testing issues and solutions, visit alltestpro.com.