Motor Starts/HR

[ptonsparky]

Ref: NEMA Standards Publication MG 10-2001



Trying to calculate the # of allowed starts per hour on a small motor. Part of the formula asks for values listed in MG1 - 12.54.

Someone have that available? My search found a place to buy the whole thing, and while that may be of benefit eventually, today isn't the day.

Yes, same project.

 

[Smart $]

Ref: NEMA Standards Publication MG 10-2001



Trying to calculate the # of allowed starts per hour on a small motor. Part of the formula asks for values listed in MG1 - 12.54.

Someone have that available? My search found a place to buy the whole thing, and while that may be of benefit eventually, today isn't the day.

Yes, same project.

I have what I believe is a copy of MG 1-2007... but there is no 12.54. It's only 6 pages of content (12 actual), 8 sections plus Annex A?which is Table 12-12.

 

[ptonsparky]

I have what I believe is a copy of MG 1-2007... but there is no 12.54. It's only 6 pages of content (12 actual), 8 sections plus Annex A?which is Table 12-12.

I downloaded the Contents & Forward of MG1-2011. 53 pages.

 

[Jraef]

Ref: NEMA Standards Publication MG 10-2001



Trying to calculate the # of allowed starts per hour on a small motor. Part of the formula asks for values listed in MG1 - 12.54.

Someone have that available? My search found a place to buy the whole thing, and while that may be of benefit eventually, today isn't the day.

Yes, same project.

I have a copy at my office, I'll PM the info for you later today when I get back from a jobsite (assuming I remember).

 

[ptonsparky]

I have a copy at my office, I'll PM the info for you later today when I get back from a jobsite (assuming I remember).

Thank you.

 

[Smart $]

I downloaded the Contents & Forward of MG1-2011. 53 pages.

I don't think my copy is the full edition, as it just covers premium motors and not motors and generators.

FWIW, here's a link to the 2009 edition, 671 pages...

https://law.resource.org/pub/us/cfr/ibr/005/nema.mg-1.2009.pdf

 

[ptonsparky]

There it is:
View attachment 11305

That will give me something to do besides drink beer.

 

[gar]

141029-1958 EDT

If your drive can provide current limiting (torque limiting) and you set this below the maximum continuous rating of the motor, then as a rough statement I would say there is no limit on the starts per hour. If you don't exceed the maximum design internal hot spot temperature then there should be no motor damage.

I believe you are concerned with your 7.5 HP motor that is normally only loaded to about 1/2 its rating. At a continuous load of 1/2 motor rating the motor temperature rise is probably about 1/4 of its full load rise assuming full motor speed. Lower motor speeds cause a higher temperature rise. If you need near zero speed at full load torque, then the motor needs an external blower.

.

 

[Cow]

That looks like a lot of math! Might be time to use a drive, then you don't have to worry about the starts!

 

[ptonsparky]

The information was more for me than the project, but it did keep me from any beer yesterday afternoon and looks like it may make a teetotaler out of me. I should have paid more attention in school. HINT...HINT to you guys just starting out.

The 7.5 appears to draw less than 1/2 at start with a loaded auger. My load is an average of 5 one second recordings. Running is 1/3 give or take.

 

[electric_cal]

Take a look at this. It should be of help.

 

[ptonsparky]

WK2 is what I am trying to solve for. I haven't had much time to study it, but that may not help me anyway.