- Occupation
- Licensed Electrician
I think it's a problem in the wiring at the jobsite.
Two speed one winding motor troubleshooting advice
- Thread starter phineascage
- Start date
- Status
I think it's a problem in the wiring at the jobsite.
MTW
Senior Member
- Location
- SE Michigan
I doubt we'll ever get to know now, after a 16 page cage match, I doubt the OP wants to step back into the ring.
Maybe you can tell us? Surely the answer must be in those numbers somewhere?
MTW
JFletcher
Senior Member
- Location
- Williamsburg, VA
The motor shop could have sent them the specs on a different motor by accident, maybe there meter or the way it reads is substantially different from the site meter, it could even be the motor shop pencil whipped their specs.
he measured the voltage, 480 at pnl, 475 at motor
when calculated using his conductor sizes, lengths and currents 470+
the currents are balanced
wire the same as the 'good' units, the motor was r$r, no wiring change
he said others said it was always like that
what prompted the rebuild (not rewind)?
the no load readings are moot without the mfgs spec
I think the motor is overloaded at hi speed
the ol's must be turned up since it is running at 115%
125 is allowed but mfgs usually recommend 100% or less, especially with a fixed load
the others are running at 95%+
bad fan bearings?
misaligned?
???
The extra 45A is there with the motor uncoupled. The fan plays no part in that.
It will be interesting to see what the motor shop come back with following the motor's return trip there.
Russs57
Senior Member
- Location
- Miami, Florida, USA
- Occupation
- Maintenance Engineer
You have the nameplate rating of the motor in the first post. It was also stated motor was repaired due to bad bearing.
OL relay will take into account service factor amps so is going to be tripping at 115% of setting.
Don’t see how anyone can defend #2 wire size despite other motors coping with it (and in fact we don’t know wiring to other motors).
OL relay will take into account service factor amps so is going to be tripping at 115% of setting.
Don’t see how anyone can defend #2 wire size despite other motors coping with it (and in fact we don’t know wiring to other motors).
no load i moot w/o knowing spec and test conditions
again
same motor
same v
same load
30% more current
mostly inductive if no load since motor pf 0.1 range
explain what would cause this?
and why it would not impact lo i?
so no load is hi
hi is hi
but lo is ok
using same coils
Defective motor.
Let's see what the motor shop comes back with.
it should only see 145 A for 110'
3.2 v drop
the 'hot' sees 157 or 3.5 v
not an issue
ampacity ~ 115
so runs hot, but so short v drop is not bad
Z will rise running hot but even if doubled only 7 v
the 500 is 2 v max so total worse case drop 10 v or so
result is 267 vs 277 or 3.6% or 462
he measure 274/474 at the motor
I wonder if he meant 2/0?
motor shop said it was ok, megger, no load i
if bad why send it back?
it runs fine on lo
carries the load on hi
and ran like this for 'what I’ve been told this has been and ongoing problem for years'
Maybe they got it wrong. And maybe there is no maybe.
The 153A on no load would ring alarm bells for me.
Shall we be patient and wait to see if they have any new findings?
so 152 and 195 no load are both valid numbers?
Patience, Sunshine. Patience.
who is impatient?
you are projecting cupcake
weg says the nla/fla is 50-65% for >200 hp dahlander (pole changing) motor
145 to 190 A
due to basically 8 pole low speed motor design
seems in range
normal 4 pole 30-40%
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