Step down transformers & efficiency?

AI Thread Summary
Power efficiency in step-down transformers decreases with voltage due to increased current, which leads to higher power losses from resistance, as described by Ohm's law. Transformer losses include copper losses in windings and core losses, which remain consistent regardless of the transformer mode. When converting from 480V to 120-208V, users can expect an increase in electricity usage of about 2-10%, depending on the specific heating unit and transformer efficiency. Modern transformers are generally efficient, operating around 98% at rated load, but energy bills may rise if additional loads are present. Overall, the efficiency loss is primarily attributed to the increased current and associated power losses.
mxtiger67
Messages
8
Reaction score
0
My question is why the power efficiency % goes down with Voltage in step down transformers.

The #of coils is less, therefore internal resistance is less too. Why the loss of efficiency in power?
I hope someone can help
 
Physics news on Phys.org
Generally it is because the current becomes larger as the voltage gets smaller. Larger current leads to more power loss via ohm's law.
 
mxtiger67 said:
My question is why the power efficiency % goes down with Voltage in step down transformers.

The #of coils is less, therefore internal resistance is less too. Why the loss of efficiency in power?
I hope someone can help

Can you explain your question a little more. I don't recognize the phenomenum you describe.
 
I guess what I'm asking is, where is the power loss, where does it go?
 
mxtiger67 said:
My question is why the power efficiency % goes down with Voltage in step down transformers.

The #of coils is less, therefore internal resistance is less too. Why the loss of efficiency in power?
I hope someone can help

Transformer losses include copper losses (I^2*R losses) in the primary and secondary windings, and the core losses (hysteresis and eddy-current losses) in the iron. These losses are the same whether operating in the step-up or step-down mode. Hence, the efficiency is the same in either mode as well.
 
I have to put a stepdown transformer in a new store.

The landlord put the wrong heating unit on the roof so i have to convert 480 Volt to 120-208 Volt power. Does anyone here know if I will use more electric because of this? Are todays transformers more efficient? Should I expect a higher electric bill? If so by what percentage?

Thanks for all your help!

Shawn
 
CurriousShawn said:
The landlord put the wrong heating unit on the roof so i have to convert 480 Volt to 120-208 Volt power. Does anyone here know if I will use more electric because of this? Are todays transformers more efficient? Should I expect a higher electric bill? If so by what percentage?

Thanks for all your help!

Shawn

Yes, you will. It depends on the specific heating unit and the specific transformer, but should be in the neighborhood of 2-10% more.
 
CurriousShawn said:
The landlord put the wrong heating unit on the roof so i have to convert 480 Volt to 120-208 Volt power. Does anyone here know if I will use more electric because of this? Are todays transformers more efficient? Should I expect a higher electric bill? If so by what percentage?

Thanks for all your help!

Shawn

Why don't you tell the landlord to change the heating unit to the correct type?

If you step up the voltage (or down) there is some power lost as described above. So yes, it will cause you to use more energy by whatever the efficiency of the transformer is.

CS
 
  • #10
I take it the existing 480-120/208V transformer was checked to make sure it was too small before a second one was added...?
 
  • #11
Thank You for all your comments!

In a way the landlord is saving me $$ by putting in a 480 Volt Rooftop unit (RTU) in. This is a 10 Ton unit needing a crane to lift and put in and a 3 month wait in manufacture, no one that we know of stocks these things. That will run direct without the Step-down Transformer. The problem arose when the contract had called for 120/208 service and the transformer before the meter was only 120/208 with no means to supply the RTU. The landlord had to dig a new trench and install 600 ft of large gauge copper wire x 4 to supply the RTU. The step-down will power all of the lighting and 110 outlets. So by your comments I will be paying a premium in electricity of 2-10% on our store feed for all the other stuff. Now you all have the complete story. PS in case your interested www.floor-n-more.com tells a little about what we do.

Shawn
 
  • #12
Transformers are very efficient when operated at rated load, usually around 98% or so. That means you'll lose 2%, i.e. use 2% more energy than you would without the transformer.

That doesn't mean your power bill will go up by 2%, unless of course you have nothing else that uses electricity in your store.

CS
 

Similar threads

Sizing an Isolation Transformer for a DC Power Supply
Replies
8
Views
2K
I Trying to understand the inner workings of a solar cell
Replies
2
Views
2K
A Why does the principle of stationary action work?
Replies
3
Views
2K
Copper Losses in an Electric Generator
Replies
5
Views
3K
Is the Transformer in My Adapter Damaged? A Question for Physics Assignment
Replies
10
Views
2K
B What Determines Induced Voltage in a Transformer?
Replies
4
Views
2K
Long distance electrical transmission efficiency
Replies
2
Views
2K
I Getting a reduced voltage from a fixed secondary voltage of a transformer
Replies
8
Views
1K
How the efficiency of transformer affects turn ratio
Replies
1
Views
3K
Help with Transformers: Understand Step-Up Coils & Voltage
Replies
25
Views
5K

Hot Threads

Recent Insights

Back
Top