strange electric motor -- idler?

I found a (very) surplus 3-phase motor today. I got a real good deal on
it because the nameplate the seller and I read the data off said it was
a 50Hz 5hp 2850 rpm motor, and he didn't believe me when I told him it
would run fine on 60Hz power. Loading it in my car, I noticed *another*
nameplate. I have never seen 2 nameplates on an electric motor before!
This one said 60Hz 7.5hp 3450 rpm! The motor is a Baldor, has that ISR
sticker on it (inverter surge rated), and has a spec number which doesn't
work on the Baldor site: 36H928-0194G1.
I want this motor for an idler for a phase converter. The largest load
motor it has to start is 3hp. This motor is pretty small physically for
a 7.5hp motor. It has a 182TZ frame. No shorts to the case. All nine
wires were disconnected so I didn't check all 72 lead-leads because the
price was so right. I'll spin it up and see, if it sparks it will be an
"oh well". I was looking for a 5hp 3ph motor for use as an idler. I seem
to have found a 7.5hp of sorts, a kind of wimpy one. I don't care as long
as it will work. But I don't want to spend a lot of effort if this motor
has something inherently non-idler about it.
Grant Erwin
Kirkland, Washington
Reply to
Grant Erwin
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It sounds like you did really well. Some of the high efficency motors appear to be much smaller than they normally would. Ive a high effeciency 10ph 3450 that is the same physical size as my high efficency Wegg 5hp and both are the same size as the several GE 1.5hp 2 speed motors I have have kicking around.
Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry
Reply to
I believe that the second plate is for export to Canada. It's rated 7-1/2hp Canadian so you have to look-up the exchange rate in the paper.
Reply to
Tom Gardner
Wow, that sucks. Machinery that changes its' horsepower up & down daily!
Reply to
Stephen Young
Naaah, Sears has been doing it for years!
Reply to
John Holbrook
Humor noted. Please get back on topic. Let me rephrase the original question: has anyone seen an otherwise-standard-looking motor labeled with 2 nameplates, one for 50Hz (e.g. @ 5hp) and the other for 60Hz (e.g. 7.5hp)?
The real question is do you think this motor is suitable for an idler for a phase converter.
Reply to
Grant Erwin
I imagine it would work fine Grant. It seems unlikely that it would have that much extra hp by upping the frequency that little bit. I have motors in my shop with different Hz ratings for speed but the amperage draw doesn't differ much and the hp is stated as the same. I read that 3450 rpm motors theoretically are not as good as 1725 rpm motors for RPCs. But, I have built an RPC for my neighbor that uses a 3450 motor. My big RPC is a 1725 motor, I think. I have another RPC that is also 1725. So maybe the slower motors are best. But the one for my
Reply to
Eric R Snow
But setting aside all the potential Canadian jokes, it makes perfect sense. All things being equal, the lower the line frequency, the more iron you need for a given horsepower.
This GE document:
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Has a table on page 5 that shows the recommended derating for using a 60hz motor on 50hz.
Reply to
Jim Stewart
I think it will work just fine for a phase converter. There has been some discussion about using 3450 rpm motors for phase converters. Some people seem to think that the higher RPM motor is better, but my opinion is that it is the physical size that counts. So in my opinion your 7.5 hp motor will act more like a 4 hp motor as a phase converter.......... But still will be fine for powering a three hp motor.
I have not seen motors with 2 nameplates, but have seen motors with data for 50 hz and 60 hz on the same nameplate.
Reply to
Dan Caster
Wow. A ten-phase motor?? What'll they think of next! :^)
Kidding aside I think you're call is right, it'll probably work fine for Grant.
How did *your* converter project turn out, gunner?
Reply to
jim rozen
Gack! Sigh..brain fart..again.
The motor is still sitting on the work bench. Between work, moving stuff out to the warehouse, the hot weather and my now apparent inablility to handle such, and a host of other inane excuses, Ive not progressed anywhere with it yet.
On the other hand..I now have more room in the shop, so I can actually do something. Its on the short list to do.
Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry
Reply to
The older I get, the more I realize that wealth in the shop is not indicated by huge piles of stuff with tiny narrow paths between the goods.
Rather, it's having huge expanses of space to waltz around in, with the same stuff artistically dotted throughout the real estate.
The implication here is I need either a) more space or b) less stuff. I can see where your though processes have led....
Reply to
jim rozen
Yeah! And Jim, Gunner ought to build hisself one 'o them naked phase converters like yours and save all that space took up by them capasators.
Bob Swinney
Reply to
Robert Swinney
The motor I used for the converter at work has both 50 and 60 HZ ratings for current and HP. Its a 5HP @ 60hz and a 4.7HP @ 50hz. The nameplate current was higher for 50hz. I've been running it for months without issue. It is high efficiency with an aluminum frame. I have accidentally left it running all weekend before, and the motor was nice and cool on Monday morning. It runs the mill and shaper quite well. I think yours would do just fine for an idler motor.
Hope this helps
Reply to
John L. Weatherly

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