Step down transformers & efficiency?

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    Efficiency Transformers
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Discussion Overview

The discussion revolves around the efficiency of step-down transformers, particularly focusing on the relationship between voltage, current, and power loss. Participants explore concepts related to transformer operation, efficiency, and practical implications for electrical systems in a store setting.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants suggest that power efficiency decreases with voltage in step-down transformers due to increased current, which leads to greater power loss via ohm's law.
  • One participant questions where the power loss occurs and seeks clarification on the phenomenon of efficiency loss.
  • Another participant notes that transformer losses include copper losses and core losses, indicating that these losses are consistent regardless of whether the transformer is in step-up or step-down mode.
  • A user inquires about the practical implications of using a step-down transformer for a heating unit, asking if it will result in higher electricity usage and costs.
  • Responses indicate that using a step-down transformer may lead to an increase in electricity costs, with estimates ranging from 2-10% more, depending on specific equipment and transformer efficiency.
  • One participant emphasizes that transformers are generally very efficient when operated at rated load, typically around 98%, suggesting that losses are minimal but still present.

Areas of Agreement / Disagreement

Participants express differing views on the reasons for efficiency loss in step-down transformers, with some attributing it to increased current and others questioning the nature of the losses. The discussion remains unresolved regarding the exact mechanisms and implications of efficiency changes.

Contextual Notes

Participants mention various factors affecting transformer efficiency, including specific equipment and operational conditions, but do not reach a consensus on the broader implications of these factors.

Who May Find This Useful

Individuals interested in electrical engineering, transformer design, or those facing practical issues with electrical systems in commercial settings may find this discussion relevant.

mxtiger67
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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
 
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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
 

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