Step down transformers & efficiency?

In summary, the power efficiency % goes down with voltage in step down transformers due to larger current being drawn, leading to more power loss via ohm's law. Transformer losses, including copper and core losses, are the same in both step-up and step-down modes, resulting in the same efficiency. If a step-down transformer is used to convert 480 Volt to 120-208 Volt power, there may be a 2-10% increase in energy usage, depending on the specific transformer and other electrical equipment in the store. Today's transformers are typically very efficient, with an efficiency rate of around 98%.
  • #1
mxtiger67
8
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
 
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  • #2
Generally it is because the current becomes larger as the voltage gets smaller. Larger current leads to more power loss via ohm's law.
 
  • #3
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.
 
  • #4
I guess what I'm asking is, where is the power loss, where does it go?
 
  • #5
It is dissipated as heat.
 
  • #6
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.
 
  • #7
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
 
  • #8
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.
 
  • #9
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
 

1. What is a step down transformer?

A step down transformer is an electrical device that converts high voltage electricity into low voltage electricity. It is typically used in power distribution systems to decrease the voltage from power plants to a level that can be safely used by households and businesses.

2. How does a step down transformer work?

A step down transformer works by using two sets of wire coils, one with a larger number of turns and one with a smaller number of turns. The larger coil is connected to the high voltage source and the smaller coil is connected to the low voltage output. When electricity flows through the larger coil, it creates a magnetic field that induces a lower voltage in the smaller coil.

3. What is the efficiency of a step down transformer?

The efficiency of a step down transformer is typically around 95-98%. This means that for every 100 units of electricity that enter the transformer, 95-98 units will be output to the lower voltage circuit. The remaining 2-5 units are lost as heat and other losses.

4. How do you calculate the efficiency of a step down transformer?

The efficiency of a step down transformer can be calculated by dividing the output power by the input power and multiplying by 100. Efficiency = (output power / input power) * 100. For example, if a transformer has an output power of 900 watts and an input power of 1000 watts, the efficiency would be (900 / 1000) * 100 = 90%.

5. What factors affect the efficiency of a step down transformer?

The efficiency of a step down transformer can be affected by various factors such as the quality of the materials used in its construction, the design and size of the transformer, the temperature and load of the transformer, and the frequency of the electricity passing through it. Higher quality materials and designs can result in higher efficiency, while higher temperatures and loads can decrease efficiency.

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