Motor Rotation CW vs CCW

[session88]

We have a 400 HP, ODP, 4160 volt, 3 phase motor that was built by the manufacture to run CCW. We have a different pump we would like to couple this CCW motor to. Problem is the different pump needs a clockwise rotating motor. Will most likely run louder. Not an issue. Will cooling be an issue with this ODP? Will the internal cooling fins not function correctly runing CW? My main concern is if this motor running CW will have close to the same torque output as it does running CCW??? Don't want to risk damaging this expensive motor. Any comments or previous threads would be appreciated. Searched previous threads for a few hours. No luck.

 

[electricpete]

I used to think directional motor rotor fans were only on 2-pole motors, but I saw one recently on a 6 pole.

If it is an ODP, there may be a chance that you can peak through the inlet air opening (with motor secured) to get a look at the rotor fan. Or else boroscope. Or else contact oem. Or else, do you feel lucky?

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(2B)+(2B)' ?

 

[electricpete]

You might also try monitor stator temperature under load by RTD. However, I am not 100% sure that RTD's in the slot will tell the whole picture if rotor fan is not properly cooling the endwindings.

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(2B)+(2B)' ?

 

[waross]

The main concern is cooling. Most induction motors have bidirectional fans. Unidirectional fans are more common on generators.
But, if the motor has unidirectional fans, it will not be cooled properly with the fans running backwards.
The best course of action is to inspect the fans. You may be able to interchange the DE and NDE fans.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[starkopete]

Hi,
I have come across (quite a few times) where the internal directional fans are reversable simple by turning them around.

Thanks.

 

[jraef]

Unidirectional cooling fans are rare. But unfortunately the only times I ever see them? Large OPD motors...



"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[macmckim]

What was the speed of the 400HP ODP motor? If it is a 2P machine, depending on the mfg and if there was a noise concern, high possiblity that motor in uni-directional.

 

[edison123]

Is the direction of rotation stamped anywhere on the motor ? If the cooling fans are unidirectional, the OEM will mark the direction on the motor, usually on the DE. Ask the OEM or post photos of the fans here.

And no, the motor torque is not affected in any way change in direction.

Muthu

http://www.edison.co.in

 

[session88]

The speed is 3565 RPM. The drive end has a direction arrow. CCW facing non drive end. (end bell) Thanks for all the info and advice. We are looking at pruchasing the correct cooling fans from the manufacture to safely run this motor CW. Hopefully the fan swap out will be something our local motor shop can handle. Was also wondering if I could purchase some portable fans made specifically to force and duct air into a motor like this for additional winding cooling?

 

[electricpete]

Regarding arrows -
Interesting to use the arrow as an indicator whether the fan is unidirectional. I haven’t heard of that, but there may be something to it.

At our plant, I think all large motors have arrows, whether directional or not. I’m not sure if we added them ourselves, or if it was part of our purchase spec. I realize of course motors without unidirectional cooling don’t care, but I thought maybe it coordinates with a connection labelplate.

I see that NEMA MG-1 requires arrow for unidirectional fan, but they don’t prohibit it for non-unidirectional.

I’m still a little unsure what to make of all that. I know at our plant, presence of an arrow wouldn’t prove anything one way or another.

================

I don’t think external fans is a good option. It is not likely it will create the correct internal cooling pattern.


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(2B)+(2B)' ?

 

[electricpete]

Also as mentioned by others, 2-pole usually does have directional fans (and no rotor vent ducts) as far as I have seen.

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(2B)+(2B)' ?

 

[edison123]

pete

"I see that NEMA MG-1 requires arrow for unidirectional fan, but they don't prohibit it for non-unidirectional."

When a motor is sold as a package in an equipment like compressor or pump, then the motor (with bidirectional fan) will be stamped for direction by motor OEM / equipment OEM / assembler.

All motors with unidirectional cooling fans are required to have the direction stamped.

Muthu

http://www.edison.co.in

 

[jraef]

Don't know if he was going to post it here or not, but the OP, as posted in another forum, found out from the motor mfr. that they just had to swap the DE and NDE fans.

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[starkopete]

If you look closely at the fans themselves they may have directional arrows on them (I've seen this from a couple of different manufacturers). If they do, as jraef suggests, simple swap the fans from one end to the other.

Thanks

 

[electricpete]

Thanks Muthu for your answers to my questions. I suspect our arrows were added by pump OEM's.

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(2B)+(2B)' ?

 

[wolf39]

Bidirectional fans are of the centrifugal type with a fan blade angle of 90 degrees. Such fans are not very efficient as far as the power is concerned they absorb from the shaft. Curved fan blades are more efficient and axial fans are most suitable for large output motors (and generators). Such motors, however, have to be directional ones, with the sense of rotation marked somewhere.

Wolf

http://www.hydropower-consult.com

 

[Ray39836]

Looks like you need to swap fans, don't forget to rebalance.