Fan cooled motor without fan

[Barry1961]

I have a .25 hp, 750:1, TEFC integral gearmotor that I want to drive very slowly by removing the fan and coupling to the stub shaft. It would be driven about 6 rpm with another very small integral gearmotor through a small clutch. A basic creep drive.

The actual required horsepower at high speed is .12 hp and the duty should be 5 minutes on and 6 hours off. Should I be worried about heat since the fan is gone? How long do you think I could run at half FLT without a fan without doing damage?

Barry1961

 

[TurbineGen]

That would depend on the ambient temperature and conditions. I wouldn't think there would be any problem in your application, but I'd keep an eye on the motor temperature just to be sure.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[electricpete]

I'm not sure I understand.

You have motor with integral gearbox. The motor has a rated speed and the output shaft has a much lower rated speed.

You will drive the motor (using fan stub) at a low speed... I assume much lower than the motor rated speed. Right?

Is this motor deenergized? If not, it doesn't sound like a good idea to me.

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[electricpete]

I suspect more likely you are just using the motor for it's gearbox... and you want to check if this unit (while denergized, but rotating and transmitting torque) needs a fan. Then I agree with TurbineGen

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[itsmoked]

I suspect it will work. But what you need to do is set it up so you can add an external fan if it's needed. Then run it with a temp gun in your hand. If the motor temp climbs rapidly to something you could extrapolate to being too hot, then you need to add that external fan.

Otherwise we can guess all day about the results.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Barry1961]

The 1/4 hp will be deenergized while the creep motor is running. The creep motor will be deenergized and disengaged, with clutch, when the 1/4 hp is running.

Thanks all!!

Barry1961

 

[MikeHalloran]

The 1/4HP will die when powered without a fan.

Mike Halloran
Pembroke Pines, FL, USA

 

[MotorVib]

I would think that you will need to derate the motor if you were using the full 1/4 hp, but with using only 1/8 hp you might not. I would run the motor for 5 min and check the temp.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[Barry1961]

I was hoping that with the low duty cycle would it not be a problem at all. But I have absolutely no real world experience running a TEFC motor without a fan. There should be room enough to mount an external fan if needed.

Barry1961

 

[fangas]

I tend to agree with Motorvib. At 50% load, and given your duty cycle. I'd try 1 or 2 cycles, measuring the temp before and after the 5 min load run, and the 6 hr off time. Also, I'd use the simple "back of hand" temp guage. If it gets hot laying the back of your hand on it, stop.

Also, be aware, the fan guard is an integral part of the fan. It directs the airflow across the frame. Without it, the fan is pretty much useless.

Good luck

Ed

 

[MotorVib]

Talking about the back of the hand test. The lab techs that I have worked with had a quick check. If you can keep you hand on a motor for more then 5 sec the temp is under was 120 deg F.

But hear is something more useful check the temp rise of the motor. For ever 10 Deg C of constent running the insulation life is cut in 1/2.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[jraef]

By any chance is this a 3 phase motor? If so, I would look at replacing that cobbled up "creep" drive arrangement with a VFD on your 1/4HP motor and run at the creep speed that way.


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[lostlazy]

I wouldn't think twice about it...