WHAT IS 3 MINUTES OF MOTOR TESTING WORTH TO YOU?
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THE COMPANY
A motor distributor in the Netherlands provided a 17 Kilowatt, 400-Volt motor to a local hospital in 2015. The hospital rented a portable crane to install the motor onto the roof of the building. The motor is used to operate a fan that is mounted on the hospital’s roof. In the spring of 2016, the motor suddenly stopped running, so the motor distributor was contacted for field service, troubleshooting, and on-site support.
THE CHALLENGE
The motor had been connected to a Variable Frequency Drive (VFD), and when the motor stopped running, the hospital’s maintenance technician reset the VFD. The motor did start, but unfortunately, the VFD shut the motor down again. Next the technician performed an insulation-to-ground test and determined the motor winding was not shorted to ground. Using a DMM (Digital MultiMeter) he then measured phase resistance and learned the phases were not open. The motor testing tools the technician used pointed to a “good” motor; therefore, they decided to replace the VFD.
After the new VFD had been installed, the motor started up, but did not continue to run. Much to the technicians’ chagrin, they were experiencing the same problem; which compelled the hospital’s maintenance manager to contact the distributor who had supplied the hospital with the motor.
The responsive motor distributor, who has a service center and support staff, sent one of their technicians to the hospital to test the motor. The service center technician used a meg-ohm meter and Digital Multi-meter (DMM) to determine that the motor was not grounded and the phases were not open; which was no different from the previous test results. Since the motor still did not run, the decision was made to replace the motor.
A crane was brought in to remove the motor from the roof of the hospital and allow a replacement motor to be installed. The replacement motor started and operated normally, confirming the new VFD was working as intended. The “suspect” motor was sent to the service center for a more thorough inspection.
