Maximum Number of Motor Starts/Hour
Maximum Number of Motor Starts/Hour
(OP)
I am working with some 50+ year old GE 100HP Squirrel-Cage motors used as an oil pump for a large generator. The info I've gathered from them include: 3-phase, 4000V, 18.2 FLA, 700RPM, 60Hz, Frame 6334Y, Type K, 10-pole, Nema Class B, Model 5K6334PL1. My question is how many times per hour can these motors be started safely?
NEMA MG-1 has some general specifications, but points to the manufacturer for more specific recommendations.
NEMA MG-1 has some general specifications, but points to the manufacturer for more specific recommendations.





RE: Maximum Number of Motor Starts/Hour
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Maximum Number of Motor Starts/Hour
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
RE: Maximum Number of Motor Starts/Hour
In the 50s NEMA frame motors were common.
When they re-rated the NEMA frames to "U" frames in 1952* they produced about 41% more power out of the same size frame.
For normal applications of large "U" frame motors, three starts per hour was generally safe and conservative.
A lot of large motors used compensator starters back in those days for hard to start loads. (Auto-Transformer starters)
DOL plugging stops and DOL plugging reversal was common with NEMA frame and "U" frame motors in the integral HP sizes.
Then came the "T" frame re-rate in 1964*. Another 41% HP out of the same size frame.
See if you can find the frame designator. That is "U" frame or "T" frame. What was normal service on many "U" frame motors would be abuse of a "T" frame motor.
If there is any indication that these were compensator start, you may want to consider retaining the compensator.
With no "U" or "T" in the frame size they may be NEMA frames. Rugged as a sledge hammer and cool running.
*- Cowern Papers;
http://www.baldor.com/Shared/manuals/PR2525.pdf
Bill
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"Why not the best?"
Jimmy Carter
RE: Maximum Number of Motor Starts/Hour
RE: Maximum Number of Motor Starts/Hour
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(2B)+(2B)' ?
RE: Maximum Number of Motor Starts/Hour
RE: Maximum Number of Motor Starts/Hour
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
RE: Maximum Number of Motor Starts/Hour
Overall, considering they are GE motors and 50 years old, the starts per hour capability of the motors are probably better than what your application requires. So, for setting a relay pick a fairly safe number like 2 starts per hour and see what happens.
RE: Maximum Number of Motor Starts/Hour
RE: Maximum Number of Motor Starts/Hour
I spent some time looking for starting frequency information on a couple of manufacturers sites with no joy.
I remember setting up the controls for a 125 HP, U frame motor driving an air compressor.
I still remember that there was a note on the name plate limiting starts to 3 starts per hour.
You have some advantages.
1> A NEMA frame is tougher than a "U" frame motor.
2> After the rewind, I expect that the windings will be rated for a higher temperature than originally.
3> Your oil pumps probably have lower inertia than the air compressor and will be easier to start.
Suggestion; See if you can get the rewind shop to specify a number of starts per hour and sign off on it.
I would be confident with three starts per hour and may go to four starts per hour while monitoring the temperature build-up on the first few motors to be started at 15 minute intervals.
But, the best and safest number will be supplied by the re-winders. I am sure that with modern magnet wire the motor will safely take more starts per hour than it would with the original wire and insulation.
If you can get guidance from the re-winders, please share it with us.
Yours
Bill
--------------------
"Why not the best?"
Jimmy Carter