2 HP motor overheating?
2 HP motor overheating?
(OP)
We have a 2 hp motor connected to a gearbox that drives a 5' shaft which had two blades on the shaft to stir liquid in a 500 gallon vessel. Management decided to have maintenance install a third "more agressive" blade on the shaft and now the motor is drawing 7.2 amps and running at a temp of 176 degrees F. This is in a hazardous location room. Am I right in being a bit "uncomfortable" with this?





RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
S! Rip
RE: 2 HP motor overheating?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
FLA 6.3, nema nom eff 82.5%
S! Rip
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
S! Rip
RE: 2 HP motor overheating?
I once got into an argument with a management type about his insisting that I increase the speed of a pump (above motor base speed) in order to make up for the fact that they had removed a 400HP pump and installed a 100HP replacement. They were shocked that the 100HP pump could not handle the peak flow conditions and were angry at me for insisting that running the pump faster would not solve their problem.
They just closed their doors last month I heard...
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RE: 2 HP motor overheating?
176 degrees F is not particularly hot. An Insulation Class B motor is good for 110 degrees C which is 230 degrees F. That is winding temp so the motor shell would have to be lower. I'm guessing here but I'd say around 205 degrees F would be a good place to quit.
Unless the motor is located in a freezing cold environment, you're going to have to reduce the amps anyway.
RE: 2 HP motor overheating?
If he used a thermal imager looking at the outside frame, the motor was a lot hotter on the inside...
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: 2 HP motor overheating?
At full motor speed, I was guessing at 25 degrees F differential temp from inside to outside. At 176 degrees outside, that would be 54 F degrees differential.
How much is reasonable? Maybe one of these motor shop guys can tell us.
RE: 2 HP motor overheating?
I have seen anywhere from 20 deg C to 60 deg C temp difference between the motor body and the winding. Motor body temperature is not indicative of the winding temperature anyway (except may be in trending on a route check). That's why none of the standards speak about motor body temperatures.
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
First of, this isn't a dual voltage 260/460 V motor, going by your earlier post. If you supply 460 V, to a 230 V motor, it will cook the motor within minutes.
Second of, even if it is a dual voltage motor, the HP of the motor does not increase by increasing the supply voltage. Your rated motor current will come down by 50% at 460 V and the percentage overload as before will still be there.
Either you ask the "management" to chip in for a new higher HP motor or remove the third blade.
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
RE: 2 HP motor overheating?
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson
RE: 2 HP motor overheating?
All this fussing about thermal curves and differential temps, etc. etc. become moot if the above is true.
There are exceptional cases (like motors running in a freezer at -20 degrees C) where you can cheat and get some extra over the nameplate rating but it doesn't sound like that kind of situation here.
Or, am I missing something?