Transformer question (between substation and home)

In summary, the conversation discusses finding the turn ratio required for an ideal step-down transformer to bring electrical energy to a home at 240V. The conversation also mentions the equations for turn ratio, voltage, current, power, and resistance in both the primary and secondary circuits. It is suggested to assume the home load as a resistance in the secondary circuit to continue with the solution.
  • #1
blooperkin
8
0

Homework Statement


A power station generates 100kW of power at a voltage of 10kV. Given that the connecting cables in the primary and secondary circuit each have a resistance of 10Ω, find the turn ratio required for an ideal step-down transformer to bring electrical energy to the home at 240V.

Homework Equations



Turn ratio:
Ns/Np = Vs/Vp = Ip/Is
(s- secondary coil, p- primary coil)

V = IR
P = V^2/R = IV = I^2R

The Attempt at a Solution


For the primary circuit,
Current = 100000/10000 = 10A
Potential difference across 10Ω resistance = 10*10 = 100V
Potential difference across primary transformer = 10000-100 = 9900VI know the power across both transformer coils must be equal, so:
Power output at secondary circuit = Power input at primary coil = 9900*10 = 99000W

- What does this 99000W refer to? The power across the secondary coil or the power across the whole secondary circuit?
- Or does the secondary coil act like cell in the secondary circuit? ie. Do I have to consider its resistance?
- Does the home act like a lightbulb in a circuit? So it has a resistance?

I'm stuck here because I can't find the potential difference across the secondary coil to use the turn ratio formula.

Diagram of secondary circuit:
fks0og.jpg
 
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  • #2
The power is going somewhere, so yes, assume the home load (resistance) is R. What equations can you write down?
 

What is a transformer and what does it do?

A transformer is an electrical device that changes the voltage of an alternating current (AC) electricity. It is used to step up or step down the voltage between a substation and a home. It does this by using two sets of wire coils wrapped around a metal core, which creates a magnetic field that transfers the electricity from one coil to the other at a different voltage.

Why is a transformer needed between a substation and a home?

A transformer is needed to change the voltage of the electricity coming from the substation to a level that is safe and usable for the home. The electricity coming from the substation is at a high voltage, which is necessary for long-distance transmission, but it is not safe for use in homes. The transformer lowers the voltage to a safer level for household appliances and electronics.

How does a transformer work?

A transformer works on the principle of electromagnetic induction. The primary coil, which is connected to the high voltage power line, creates a magnetic field when electricity flows through it. This magnetic field then induces a current in the secondary coil, which is connected to the low voltage line going to the home. The number of turns in each coil determines the voltage change.

What are the different types of transformers?

There are three main types of transformers: step-up, step-down, and isolation. Step-up transformers increase the voltage from the primary to the secondary coil, while step-down transformers decrease the voltage. Isolation transformers are used to isolate the electrical circuit from the power supply, providing a layer of protection against electrical shocks.

What are the safety precautions for transformers?

Transformers contain high voltage electricity and should only be handled by trained professionals. It is important to keep a safe distance from transformers and to never touch them or any wires connected to them. If you notice any damage or overheating of a transformer, it is important to contact your local utility company immediately for repairs.

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