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Max winding temp

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lighthunter:
Update:

Thanks again Pete for all the ideas and thoughts on this one. All attempts to adjust the volt/amp curve via vfd programming failed as the OEM disallows it. Weve yet to get any real support from those people.

 The compressor has been running fine for a while now. I drilled a hole near the bottom of the end frame and put compressed air to it so it blows cool air through the cage out the cover of electrical box. A co-worker drilled the fitting a bit larger as the cooling requirement was higher than i had anticipated. It takes around a 6hp efficiency hit just to cool it but it works. Runs about 175F now. Whats difficult for me is knowing exactly whats ok? A different unit had oiltemp that reached 221F today. Pressure washed cotton fuzz from radiator and now at 196 where thermostat regulates it. Maybe its fine for winding temp to be 250F no one i know will go there and articles written about it tiptoe around the subject. Oddly most manufacturers do not put temp sensors in windings yet a common house fan includes this as a safety device. A thermal cutoff or tco. As i write this im reminded of an event years ago... 1998... how time has gone... when a laser roots blower also siemens motor, failed due to a temp sensor in winding. I jumpered and machine ran, i ordered a temp switch in a T0220 package and inserted/epoxyed into winding at end of motor seems like i started at 110C and kept having to order higher ones till i got one that didnt trip under normal circumstances. Seems like the number was 115 or 120C when i finished and that one ran for years that way. So by that info i can set this at 250F and reduce the orfice size to maybe 4HP of cooling. Of course an air booster in reverse trading pressure to volume would reduce the flow requirement again.  Anyone else agree i can increase thermal trip point to 250F or 120C?

I kinda feel stupid i forgot the eqperience i learned back then about winding temp.

Perhaps i better ask the elder gentleman what class wind wire he used for this one.

Its not an ideal solution but it is a solution and it does run welll now. Anyone have an idea on a moisture sensor for air line. I will need it to fault on humidity as moisture will kill windings too. So far our dryer is flawless but theres no feedback to stop anything if it doesnt remove all moisture.

Hope everyone is doing well, i havent had much time to post as garden, work and other odd jobs have been over the top lately.

Pete:
Hi Lh, well that was a novel solution.
Here is a link to a page about winding insulation temperature ratings.
A H class winding will have White Nomex slot insulation. The rest of the insulation will be mica or fibreglass for phase insulation and leads.
Pity that Siemens pack the motors windings in too tight and fit too big a motor into a small frame.
Gone are the days where open frame motors could be run at double their ratings. Nowadays the ratings are absolute max.
I hope you are well and that the workaround stays working.
I guess some sort of air dryer like spray painting sets have could work but sounds like you are putting a lot of air into the motor.
Cheers
pete
https://www.hecoinc.com/blog/electric-motor-insulation-class-what-is-it

lighthunter:
Hey Pete, that Heco document is wonderful.  We still have no email service where i work so have not gotten info on winding class yet. Because the alarm temp control i put in only has a max setting of like 209F thats what i set it to. It runs at about 185°F so am real happy with it now. The motor current at 60 hz 3600ish rpm is 200A, nameplate is 166A, thats a bit concerning but it doesnt have to run there very often.
Again that heco document is better than any i had found on the subject.

 The heat here is crazy lately like near 100 with high humidity but it rained last night so its been nice today. Crops are doin great. Its hard to make it through June without your garden being wiped out by drifting farm chemicals but this year is a bit better, lost some peppers but the rest pulled through. Even the apple trees have leaves still looking like a leaf rather than the gnarled curled shape they usually get from sprays. Ha for years i thought it was cedar apple rust until i finally caught on to it. Hope everyone is doing well!

rossw:

--- Quote from: lighthunter on June 25, 2022, 07:05:10 pm ---Crops are doin great
--- End quote ---

Hah, you're lucky.
Where I am, the *WEEDS* are doin' great. Other things ok, but weeds are going bonkers!

Pete:
Spray drift eh. I was talking to a beekeeper years back and he was totally confused because he lost something like 100 hives and could not work out what caused it.
I asked him where they were and if there were any tree plantations nearby. He told me and I knew his problem straight away.
Spray drift from the plantations was it.
The plantations were sprayed regularly with a chemical called Alphacypermethrin. It is used to kill the eucalypt beetles that eat the trees.
Well as we know if it kills one insect it kills them all and the bees were not far from the plantations.
I had a friend who had his whole crop of Flowers that he had been selectively breeding for 20 years wiped out by the farmer next door spraying 2-4-D.
The farmer denied it but also happens to run a dairy and has a well frequented cheese factory. Unfortunately for my friend and his 20 year Hellebore  program the farmer was from a rich family with political connections and nothing was done about the spray drift.
Our state claims to be a Clean Green state, but nowhere is safe from chemical sprays.
Glad the documents are helping and hope the problem with the motor stays fixed
Pete

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