Transformer engineering problem

In summary, the problem is that the person is trying to calculate the power out, given the input power and efficiency, but their internet homework submission page is saying that the answer is not correct.
  • #1
neraketam
2
0
Homework problem:
A transformer on a pole near a factory steps the voltage down from 3900V to 220V. The transformer is to deliver 1180kW to the factory at 91% efficiency. Find the power delivered to the primary in kW.

What I've done:
Well, I thought that power in equals power out. So I worked all the math to prove that and used P=IsVs, solved for Is then used that to find Ip (Ip=VsIs/Vp). Then found P=IpVp. I got 1180kW! I then calculated in the efficiency--not correct. And then in the follow up question, I found out that my Ip isn't even correct. What's wrong here?
 
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  • #2


Originally posted by neraketam
Well, I thought that power in equals power out. So I worked all the math to prove that and used P=IsVs, solved for Is then used that to find Ip (Ip=VsIs/Vp). Then found P=IpVp. I got 1180kW!
Sounds like you are going in a circle.

True, power in = power out for an ideal transformer. A nonideal one will waste some of that power. If I read the question correctly, the first part just asks for what input power is needed to get the output power given, given the efficiency:

Pin X 0.91 = Pout
 
  • #3
transformers

I did that but my silly internet homework submission page is saying it's not correct. That is not the first time it's said that so...at least I know I'm doing the problem right and thanks for getting back to me so quickly!
 
  • #4
You don't need to know anything about voltage and current to do this. All you need to know is the power out and the efficiency. It is supposed to be 1180 Kwatts out. So, figure the efficiency from that. Can't help you with your internet problem though. Sorry.

P.S. Why did I just post this when Doc Al did it so nicely with just a formula?
 

FAQ: Transformer engineering problem

What is a transformer and how does it work?

A transformer is an electrical device that is used to transfer electrical energy from one circuit to another through electromagnetic induction. It works by using two or more coils of wire, known as the primary and secondary windings, that are wound around a common iron core. When an alternating current is passed through the primary winding, it creates a changing magnetic field, which in turn induces a current in the secondary winding, allowing for the transfer of energy.

What are the common problems with transformers?

Some common problems with transformers include overheating, insulation breakdown, and winding faults. Overheating can occur due to excessive load or poor ventilation, while insulation breakdown can be caused by aging or external factors such as lightning strikes. Winding faults can be caused by physical damage or manufacturing defects.

How do you diagnose a transformer problem?

Diagnosing a transformer problem typically involves a combination of visual inspections, electrical testing, and thermal imaging. Visual inspections can reveal physical damage or signs of overheating, while electrical testing can identify issues such as insulation breakdown or winding faults. Thermal imaging can also be used to detect hot spots, which can indicate potential issues.

What are the factors that affect transformer performance?

The performance of a transformer can be affected by various factors, including load, temperature, and insulation. Higher loads can cause the transformer to overheat, while extreme temperatures can affect the insulation and lead to failures. Other factors such as the quality of the materials and manufacturing process can also impact performance.

How can transformer problems be prevented?

Regular maintenance and testing can help prevent transformer problems by identifying potential issues before they escalate. This can include visual inspections, electrical testing, and oil analysis. It is also important to follow proper installation and operating procedures, as well as ensuring the transformer is not overloaded. In addition, using high-quality materials and following industry standards can help prevent problems.

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