Motor life, depending on applied voltage? 3

[IanAnd555]

Hi everyone, this is my first post.
My boss asked me today to someone find out the answer to this question.

If I have a motor rated at 120V, would it necessarily "hurt" the life span of the motor if it was run at say, 110V?

I do not have a specific motor in question, I'm just thinking that someone here has maybe had experience with using a motor at a voltage other than the one specified.

Anyone run into anything like this before? Any wisdom to shed on the subject? Any help is good help!

Thanks!
Ian

 

[dpc]

Possibly. What most shortens the life of a motor winding is heat because heat degrades the winding insulation over time. The hotter the motor runs, the shorter its life, everything else being equal.

Running a motor at a lower voltage generally results in more current draw by the motor to produce the same power output. Higher current creates more resistive losses in the motor and more heat.

Of course, too high a voltage creates its own problems, such saturation, etc.

 

[itsmoked]

To make a valid determination you would need to measure the motor's current draw. If it is below nameplate current then likely there would be no perceptible reduction in life.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Agreed.

 

[jraef]

All true, but it should also be noted that, at least here in North America, NEMA standards for motor design state that a motor should be capable of tolerating a voltage of +- 10% of rated. So a 120V rated motor getting 110V is within that tolerance range and the user should expect no noticeable decrease in life expectancy if run at rated load or less. For that reason, you will see most "120V" motors are actually rated at 115V, because then they can be hooked up to anything from 104 to 127V.

If the motor is truly rated for 120V, there is of course not much chocolate left in that "fudge factor", so if the 110V drops another 3% (which utilities do on a regular basis) to below 107V, you are at serious risk of letting out the magic smoke.


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

For reference, this is from one of the Cowern Papers on the effects of voltage variation in AC motors.

"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

 

[IanAnd555]

Thanks guys! Very helpful