Picture 1 - The dull segments are where the bars were not connected.

Picture 2 - The evidence of shorts in the original rotor bars

Picture 3 - The end product from Houghton International

One client is an overseas power generation company who were experiencing rotor failures on their 3.3kV PA Fan motors on a regular basis.

Client Problem
On analysis, we found the rotor has been poorly braized by the previous repairer, leaving an open circuit in roughly ten bars (see picture 1.)

As such, the rotor bars were shorting in the slot because they weren't properly connected to the end rings. (See picture 2.)
The knock-on effect was increased pressure on the windings and differential expansion in the other rotor bars, leading to failure.

The Houghton International Solution
We also analysed the motor's starting characteristics and made a recommendation that the number of starts should be limited to 3 per hour to reduce the likelihood of thermal expansion cracking bars with too many shock loads and high start-up currents.

Our puddle braizing technique meant the repaired rotor was more able to cope with its arduous workload, and will run for many years to come. Picture 3 shows the finished product.