# Thread: you're wrong. no you're stupid. well you're stupider so there.

1. Originally Posted by topgone
These things here got me confused. Why do other people here claim that the setup is okay when the OP mentioned "it failed"? Did I miss a lot?
failure not = burned up, damaged or over temp
he was told the output was clamped at 840 kva, not possible
it started and ran the motor fine
he did not know how they ascertained that
we do know where the 840 was measured, makes a big difference
filter takes 50-60 kva
xfmr consumes 40 or so

2. Senior Member
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Originally Posted by Ingenieur
failure not = burned up, damaged or over temp
he was told the output was clamped at 840 kva, not possible
it started and ran the motor fine
he did not know how they ascertained that
we do know where the 840 was measured, makes a big difference
filter takes 50-60 kva
xfmr consumes 40 or so
For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.

3. Originally Posted by topgone
For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.
I am having trouble with that math! Your transformer to motor ratio is only slightly higher than the OP (1.17 vs 1.28).

I dont think it ever went over temp. Here is what the OP said:

. I've never seen it before, usually it just runs over temp.
The way I read that, if you take into account the previous and next few sentences, he wasnt saying that his transformer went over temp. He was saying, in general overtemp is what he sees on an overloaded transformer versus the "current limit" phenomenon he thinks he is seeing now.

4. Originally Posted by Fulthrotl
1HP = 746 watts.
1,000 HP = 746,000 watts.

that's not allowing for any losses whatsoever.
no heat, transformer loss, zip.

125% would be 932,500 watts.
Agreed. The transformer simply isn't big enough regardless of any other problems that there may be.

5. Senior Member
Join Date
Feb 2013
Location
India
Posts
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Originally Posted by Besoeker
An 875kVA transformer isn't big enough for a 1,000 hp motor. If you were in the business of designing drive systems you would have no difficulty in understanding that.
The OP question is 840KVA limitation of 875KVA transformer. My proof is no evidence other than OP statement existed for it.

6. Originally Posted by topgone
For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.
???
665/850 = 0.78
746/875 = 0.85
1.09 or 9% more
moot
when converted to kva for eff/pf for this motor range
BOTH are ok
Last edited by Ingenieur; 11-15-17 at 03:55 PM.

7. Originally Posted by Fulthrotl
1HP = 746 watts.
1,000 HP = 746,000 watts.

that's not allowing for any losses whatsoever.
no heat, transformer loss, zip.

125% would be 932,500 watts.
so?
the xfmr is rated in mva
the motor depending on measuring point
is between 740-840 kva both < 875
filter loss 60 kva
xfmr 40 kva
calcs http://forums.mikeholt.com/showthrea...52#post1871852

drive mfgs (link previously posted) state xfmr kva >= motor kva
which it is
and the filter reduces stress on the xfmr

no one can say the xfmr is too small
the data indicates otherwise

8. Originally Posted by Ingenieur
failure not = burned up, damaged or over temp
From the OP:

"usually it just runs over temp."

I don't know why you continue to ignore that.

9. Originally Posted by Besoeker
From the OP:

"usually it just runs over temp."

I don't know why you continue to ignore that.
why do you misrepresent it?
he said 'usually', but not in this case, in this case output was clamped at 840 kva
impossible

10. Originally Posted by electrofelon
...
I dont think it ever went over temp. Here is what the OP said:

I've never seen it before, usually it just runs over temp.

The way I read that, if you take into account the previous and next few sentences, he wasnt saying that his transformer went over temp. He was saying, in general overtemp is what he sees on an overloaded transformer versus the "current limit" phenomenon he thinks he is seeing now.
I'm not the only one
imo it was NOT over temp
only output limited (impossible in this case)

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