Large AC Squirrel-Cage Induction Motor Repair Versus Repalce 1

[engineerithink]

Hi All,

I was wondering if anyone knew of any books/websites/whitepapers/etc. which can direct me on making an informed recommendation to repair or replace large voltage AC squirrel-cage induction motors. What I am particularly interested in are approximate cost estimates for replacing different components of the motor like the rotor, stator, or bearings. I understand that there are many factors which determine cost such as availability of materials and demand for repair work. However, if I have approximate cost I can determine whether or not I should even bother requesting a quote to repair the motor. Something as simple as repairing rotor bars usually equals x amount of dollars will do fine. This way I can say something like the downtime to repair the motor plus the approximate cost to replace ___ motor components justifies replacing the motor instead of repairing it.

Thank you!!!

 

[engineerithink]

Thanks all,

In this instance, we are replacing a 1250hp boiler feedwater pump motor fed from our 2300V switchgear. One of the biggest reasons why I suspect O&M wants to replace the motor is because it was installed in the early 60's.

 

[stephenw22]

Just because a motor is 40-50 years old doesn't really mean anything. If everything is still in good shape, there's no reason to think it won't last another 40-50 years. We have some motors on our site that have been running well for around the same length of time, without anything but regular maintenance.

It might be worth it to do some thorough testing on the motor. I'm not sure about the efficacy of on-line testing for finding motor faults or wear, but I'm sure someone else here could answer that.

Also, at 1250HP, you may be able to re-wind and re-rate the motor to higher power and better efficiency. We've rewound a couple of large compressor motors here with good results. It was done before my time, but I recall that we were able to give a pretty substantial boost to the motor HP.