Background

Should I Replace or Repair My Electric Motor?

Does rewinding a motor harm its efficiency?

A two year study conducted by EASA (Electrical Apparatus Service Association ) shows that there is no significant loss in motor efficiency when quality rewinding procedures are followed. They found that in some instances, the motor efficiency actually increased.

EASA decided to do this study because there was no documented evidence to prove or disprove that a rewound motor will lose efficiency.

The study was conducted by an impartial third party under controlled circumstances. The testing was conducted on motors from 7.5 horsepower to 300 horsepower. They focused on motors with higher power ratings, as these were the most likely to be rewound.

Motors that were rewound without explicit control on stripping and rewind lost efficiency ranging from -0.3 to -1.0 percent. When controls were put into affect, the losses decreased and some even increased. The range was -0.1 to +0.2 percent. Motors that were rewound multiple times using quality rewind procedures had efficiency changes of -0.1 to +0.8 percent.

Nine Steps in Controlling Rewind Efficiency:

Burn Out Process
Temperature and time must be controlled to ensure a clean core. This will avoid degrading the interlaminary insulation.

Coil Removal
Proper coil removal eliminates damage to the laminations and decreases the chance for stray losses.

Conductor Cross-Sectional Area
Never reduce the cross-sectional areas when changing the wire gauge as this increases I²R losses.

Mean Length of Turn
Failure to control (MLT) can increase stator I²R losses.

Changing Winding Configuration
I²R losses, core loss or stray loss should not increase in a winding change.

Bearing Lubrication
Avoid over lubrication and mixing non-compatible greases, follow mfg's recommended schedules.

Fans
Replacing a fan with other than original design can increase windage loss , temperature rise and I²R losses.

Catastrophic Damage
Evaluate production loss, energy costs and operational costs before you decide to rewind a motor with catastrophic damages.

Core Losses
Measuring core loss before burn out and after core stripping and cleaning will identify significant increases in core loss.

7 Reasons why Kalen Electric rewinds are better than new:

  • All motors are repaired to EASA Premium Efficient Guidelines.
  • Core loss testing before and after burnout
  • Only Premium Class H Inverter Duty Insulation Systems are used.
  • Each motor is individually remanufactured to our Customer's repair specifications.
  • ISO Grade G0.4 premium rotor balance.
  • FFT Vibration reports.
  • Complete documentation of Failure/Repair/Test results.

EASA's rewind study is good news for the customer. Now we have technical proof that motors can be rewound without a loss of efficiency. The study shows customers they have an option when their motor fails. They can chose to rewind it or they can chose to replace it.

Questions? Call us today if you need assistance at 541.345.1579