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Motor Repair

Successful repair of a polyphase machine requires the usual amount of matter-of-fact operations to replace bearings, rewind a rotor or stator, balancing and testing to complete the repair.  Most larger repair shops are equipped to do these operations and are very successful at this, quickly returning the machines to service.

Issues beyond these elementary problems require a further understanding of machine operations and manufacturing techniques.  If un-corrected, they often lead to continuing failures and loss of productivity.  Depending on the repair center’s experience, these issues may not be recognized nor properly corrected.

AC Motor Technologies, Inc. has provided technical support for the service centers beyond the matter-of-fact and successfully corrected these issues.  For example:

2-Pole Motor vibration at temperature.
 A large 2-pole induction motor rotor was rebuilt using identical parts.  During test, the motor exhibited high vibration at temperature.  AC Motor Technologies, along with the Service Center, disassembled the motor and created an assembly drawing from the parts.  An internal clearance was found to be incorrect and the part re-machined.  This not only corrected this issue, but gave the service center guidelines for the repair of future units.

Large Low-Speed Synchronous Motor failure.

 A large synchronous motor which had been operating poorly was taken to a service center for repair.  Upon disassembly, the motor was found to have failed field winding connections, a stator winding ground and failures in the brushless exciter rectifier.  AC Motor Technologies was able to explain the failures, configure a more effective solution, and guide the exciter rectifier repair process.  The motor was returned to service and now is running “better than ever before”.

Synchronous machine testing

 One service center had been asked to test a synchronous motor to demonstrate the effectiveness of their repairs.  AC Motor Technologies prepared a test equipment plan to permit this kind of testing in the future.  This included test equipment configurations, connections, and an excitation supply for any type of synchronous machine.  Procedures were identified to permit starting at reduced voltages and then testing to produce a confirming “V” curve.  This service center now regularly tests synchronous machines and is becoming a know “center” for this type of work.  Their capability is now being expanded to include brushless exciter-rectifier repair and testing.

Induction Motor Rotor Failure

 A large vertical induction motor rotor had failed in each of 5 identical units which were being powered by adjustable frequency drives.  AC Motor Technologies participated in the discovery that the rotor bars were loose and resonated at a drive harmonic produced at the start-up frequency of the drives.

Synchronous motor exciter rectifier failures

 A 1250 Hp synchronous motor had a history of rectifier failures and synchronizing difficulties.  The synchronizing process was taking a minute or two to complete.  This resulted in failure of the exciter rectifier due to over temperature.  Replacement of the control with a Trigger-1 module and a reconfiguration of the exciter field current supply successfully resolved the issue.

Brushless Exciter-Rectifiers

AC Motor Technologies, Inc. now accepts exciter-rectifiers for repair, overhaul, and testing. Without parts, cleaning and testing can be done in one or two days for rectifier diameters up to 15”. Modifications, mechanical parts replacements, semiconductor replacements and control replacements will be identified and additional cost/time to complete the repair determined.

Repair Centers

 AC Motor Technologies, Inc. has been working with a few good Repair Centers.  These include:

  • Jay Electric Co.                               Birmingham, Alabama
  • Malloy Electric                                 Sioux City, Iowa
  • Birclar Electric                                 Romulus, Michigan
  • GE Service Center                         Tucson, Arizona
  • Kiemile-Henke                               Dayton, Ohio
  • Integrated Power Services           La Porte, Texas
  • Integrated Power Services           Rock City, South Carolina
  • Kiemle-Hankins                             Monroe, Ohio

Find a good Service Center near your location – AC Motor Technologies can help them to make your Motor right!