1 - 20 of 21 Posts

#### Redlog

·
##### Registered
Joined
·
2 Posts
Discussion Starter · ·
Hi All recently <i got a huge electrical bill and am now trying to figure out where <i am using all the power. <i have figured some of the usage but am trying to figure out how to determine the wattage of several transformers that <i have.
<i have several 75kva 600v 3 phase transformers and a couple 45 kva 600v 3phase transformers.
Can someone tell me how to calculate the wattage of these?:vs_worry:

#### mm11

·
##### JW
Joined
·
428 Posts
The power is already calculated. 75kVA and 45kVA. This sounds like a commercial installation...

#### Daniel Holzman

·
##### Civil Engineer
Joined
·
5,832 Posts
Transformers convert voltage from one level to another. They consume only a small amount of power due to losses within the transformer. Most unlikely that transformer losses represent a significant part of your electric bill.

#### sparky48

·
##### Electrician (Retired)
Joined
·
111 Posts
The "K" stands for 1000
The "VA" stands for watts
So 1000 X 75 = 75,000 watts
1000 X 45 = 45,000 watts

#### mm11

·
##### JW
Joined
·
428 Posts
VA does not stand for watts.

#### Redlog

·
##### Registered
Joined
·
2 Posts
Discussion Starter · ·
I am still a bit confused I realize that the transformer converts power and in this case it steps it down from 600 volts to 120/208 for me. We get billed for electricity used and these transformers must use an amount of wattage to operate. I understand that w=V x A So in my case in the conversion that 600v x 72.2 amps (nameplate) = watts that this transformer produces ?

#### jbfan

·
##### Super Moderator
Joined
·
9,988 Posts
The power the transformer uses is minimal.

The power you are paying for is what is connected to the transformers.
You can have these transformers, but not use the full capacity of them.

What kind of business is this?
How much more is the bill than before?

Have you contacted the power company?

gregzoll

#### micromind

·
##### Idiot Emeritus
Joined
·
1,910 Posts
There are 2 Watt ratings on transformers, operating and parasite.

The operating Watts is Watts out = Watts in. This is determined solely by the load downstream of the transformer. This can be anywhere from zero on up.

The parasite rating is Watts in and 0 Watts out. This is what the transformer 'wastes'.

In actual operation, Watts in will always be higher than Watts out. This is because all transformers produce heat and this heat comes from Watts in but is not converted to Watts out.

In my experience, the parasite load of a 45KVA transformer is roughly 10 KWhrs per day. a 75 would be about 15.

The amount billed will never be less than the parasite load, and any amount more than parasite is actual usage.

Lets say you have 3 - 75s and 2 - 45s. That's roughly 65 KWhrs per day, or nearly 2000 KWhrs per month plus the actual usage. If you're paying 10¢ per KWhr, that's \$200 a month as an absolute dead minimum. Add the actual usage on top of that and you can see why it's expensive.

Rob.

P.S. Unless you're being billed for VARs or low Power Factor, VA (or KVA) has nothing to do with the bill, it's all Watts.

#### jimn

·
##### Registered
Joined
·
1,456 Posts
What electric rate are you on? Commercial rates often come with demand billing . The higher your peak demand draw is in a billing period, the more you pay per kWh . For example our little theater has a 400 AMP three phase service. We have the theater light system with enough instruments to create 280 AMP load. We also have 4 5 ton HVAC units . Bring up the theater lights as one of those 5 ton units fire up and the cost for every kWh that month goes through the roof.

#### TimPa

·
##### Registered
Joined
·
589 Posts
OP realize that a transformer will use power, even when you are not using it's output to operate any devices. so if you are not using the 120/208, turn off the supply to the transformer.

#### TimPa

·
##### Registered
Joined
·
589 Posts
Hi All recently <i got a huge electrical bill and am now trying to figure out where <i am using all the power. <i have figured some of the usage but am trying to figure out how to determine the wattage of several transformers that <i have.
<i have several 75kva 600v 3 phase transformers and a couple 45 kva 600v 3phase transformers.
Can someone tell me how to calculate the wattage of these?:vs_worry:
the VA x Power Factor = watts. PF is less than 1.

#### sparky48

·
##### Electrician (Retired)
Joined
·
111 Posts
VA does not stand for watts.
I simple form VA stands for Watts. I don't care how you want to twist it. So then in my calculation is the xfrmr 75000 watts and 45000 watts or do you come up with something else???? Give me a break.

#### gregzoll

·
##### Banned
Joined
·
17,158 Posts
The "K" stands for 1000
The "VA" stands for watts
So 1000 X 75 = 75,000 watts
1000 X 45 = 45,000 watts
Incorrect. "The ratio between the VA (i.e. rms volts time rms amps) and Watts is called the power factor PF. In other words, volt-amps x power factor = watts. Similarly, KVA*PF = KW, Or kilovolt-amps times power factor equals kilowatts."

http://www.rapidtables.com/calc/electric/kva-to-watt-calculator.htm

#### gregzoll

·
##### Banned
Joined
·
17,158 Posts
I simple form VA stands for Watts. I don't care how you want to twist it. So then in my calculation is the xfrmr 75000 watts and 45000 watts or do you come up with something else???? Give me a break.
It never has stood for watts. As for a break, yeah you will get your chops broke and ribbed for a while by some of the sparky's. Just let it roll and laugh. All of us have had brain farts every now and then. Sometimes stating it on a forum not how you are thinking of it in your head, comes out a little wrong. You just have to do the math on this one.

#### Daniel Holzman

·
##### Civil Engineer
Joined
·
5,832 Posts
Watts is a measure of real power, VA is a measure of apparent power, which depends on the reactance in the circuit. The comment about watts = V x A x P where P is the power factor is correct for a single phase AC circuit. The power factor depends on the inductance and capacitance of the devices on the circuit. Most AC circuits, especially ones including inductance motors, will have a power factor well below 1.

The net effect is that a transformer rated at say 1000VA will only be able to deliver 1000 watts when the circuit has zero reactance. Typically, the transformer will be able to deliver less than 800 watts (real power). For a good discussion about apparent power, true power, reactance, capacitance, inductance, see http://whatis.techtarget.com/definition/volt-ampere-VA.

None of this is relevant to the question of why the OPS has a higher than normal power bill, as the losses through transformers are not likely to contribute a significant amount to the monthly power bill. There may be complicated factors such as time of day billing or peak demand billing that are impacting the bill, but unless there is something wrong with the transformers, the lost power through the transformers is a small but unavoidable cost of transforming voltage.

#### gregzoll

·
##### Banned
Joined
·
17,158 Posts
Hi All recently <i got a huge electrical bill and am now trying to figure out where <i am using all the power. <i have figured some of the usage but am trying to figure out how to determine the wattage of several transformers that <i have.
<i have several 75kva 600v 3 phase transformers and a couple 45 kva 600v 3phase transformers.
Can someone tell me how to calculate the wattage of these?
A huge bill in your hand, could be not so large in someone else's. When a transformer are looked at as a certain percentage of loss from the stepping up or down, the energy loss is converted to heat or BTU's. That is why you see the radiators on them.

The loss of power from transfer is already calculated by the power company, when they bill businesses so much per kWh.

"Typically, the total losses for a 75 kVA transformer are about 1,000 W at 35% loading or 1.3%. The actual losses when the transformer is fully loaded can be more than 3,000 W for linear loads and 7,000 W for nonlinear loads. This amounts to 4% and 9.3% respectively—considerably more than the NEMA TP-1 table for minimum efficiencies for a 75 kVA transformer. While the overall concept for requiring more energy-efficient transformers is quite good, engineers may want to be very careful about transformer selection when the anticipated operating conditions do not match the base criteria that were used in developing the TP-1 table."

http://blog.schneider-electric.com/...ncy/2013/03/25/how-big-are-power-line-losses/

http://www.csemag.com/single-articl...-losses/84a7466f05abe1341ddb4b5a402249e9.html

#### gregzoll

·
##### Banned
Joined
·
17,158 Posts
You have to know Ohm's law and also Coulomb's law regarding electrical force and also Newton's laws of motion, to really grasp the concept of how the transformer works in playing into the use of electricity by a transformer and a structure, whether it is at an idle state or a load is used.

Transformers are going to always use some amount of electricity, regardless if you have a load on them that is off. Think of it like a garden hose waiting to be turned on.

http://www.copper.org/environment/sustainableenergy/transformers/education/trans_losses.html

#### gregzoll

·
##### Banned
Joined
·
17,158 Posts
I simple form VA stands for Watts. I don't care how you want to twist it. So then in my calculation is the xfrmr 75000 watts and 45000 watts or do you come up with something else???? Give me a break.
You have to remember a little thing called Ohm's law. No one is twisting it around, except that you are not calculating it correctly. Yes watts is the energy, which is converted to BTU's. That is why during the Summer months when it is really hot outside and everyone wants to run their A/C, they have to cool the suckers off, otherwise you can fry eggs on them.

#### dmxtothemax

·
##### Registered
Joined
·
5,468 Posts
Hi All recently <i got a huge electrical bill and am now trying to figure out where <i am using all the power. <i have figured some of the usage but am trying to figure out how to determine the wattage of several transformers that <i have.
<i have several 75kva 600v 3 phase transformers and a couple 45 kva 600v 3phase transformers.
Can someone tell me how to calculate the wattage of these?:vs_worry:
A much simplier answer -

va = w
K = 1000
so 75kva = 75,000W.
&
45Kva = 45,000W.

Is this what you wanted to know ?
if not please elaborate.

:vs_cool:

#### Know A Little

·
##### Registered
Joined
·
714 Posts
But the point of this whole thread is not about your transformers but about what loads you are feeding and your past and present bills I ASSUME.

What was your low bills KWHR?

What is the high bill KWHR?

What is your rate per KWHR?

Do you have a power factor penalty?

Do you have a demand charge?

My old license plates

1 - 20 of 21 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.