I recently installed a 480vDelta/208vWye 112.5kva xfrmr back-fed to supply test equipment for a lab. The 68kva load is only turned on about 1hr/month, but the customer is complaining about his power bill showing +/- 1kw-hr consumption when "not in use", or about $90.00 / month. Is it normal for a transformer to consume power, albeit <1%, while under "no-load" situations? My amp-probe confirmed this consumption. I recommended switching off the Main when not in use, but I'm concerned that the CB is not switch rated. Ideas or -gulp!- lessons anyone?
Transformer consuming power w/o load
- Thread starter photon
- Start date
- Status
Re: Transformer consuming power w/o load
No load losses it is. It takes power to magnetize the transformer. A typical 150degC rise 112.5kva dry type distribution transformer will have a no load loss of 600w with a total loss at full load of just short of 4000w.
But contrary to what one would expect an 80degC rise transformer may have a NL loss of 700w which is more than the 150degC unit. However the total losses for the 80degC unit may be a little less than 3000w or 20-25% less than the 150degC unit.
No load losses it is. It takes power to magnetize the transformer. A typical 150degC rise 112.5kva dry type distribution transformer will have a no load loss of 600w with a total loss at full load of just short of 4000w.
But contrary to what one would expect an 80degC rise transformer may have a NL loss of 700w which is more than the 150degC unit. However the total losses for the 80degC unit may be a little less than 3000w or 20-25% less than the 150degC unit.
Re: Transformer consuming power w/o load
Prove it to yourself...put an amprobe on the primary and "see" the current draw.
We had a customer who had a 300kva XFMR in use with no load for a long time. When we discovered it, we turned it off and saved him about $150/mo on utility bill.
Prove it to yourself...put an amprobe on the primary and "see" the current draw.
We had a customer who had a 300kva XFMR in use with no load for a long time. When we discovered it, we turned it off and saved him about $150/mo on utility bill.
caosesvida
Senior Member
Re: Transformer consuming power w/o load
I did that experiment with a welder I had, a cracker box. it drew about 3 amps just idleing. something to think about. Just imagine the computers and printers all idleing across the world, maybe we don't need so much oil??
I did that experiment with a welder I had, a cracker box. it drew about 3 amps just idleing. something to think about. Just imagine the computers and printers all idleing across the world, maybe we don't need so much oil??
- Status