Transformers Current and Voltage

In summary, a transformer with a turns ratio of 5:1 and 90% efficiency is connected to a 230 V supply and has an output current of 2.7 A. Using the equation for efficiency, the secondary voltage can be calculated. The output power and input power can also be determined, and the input current can be found by accounting for the efficiency.
  • #1
xvivi
1
0

Homework Statement


A transformer has a turns ratio of 5 : 1. It is connected to a 230 V supply and an output (secondary) current of 2.7 A is measured. If the transformer is 90% efficient, calculate:
  1. Secondary voltage
  2. Input (primary) current
[/B]

Homework Equations


Pout/Pin*100=efficiency[/B]

The Attempt at a Solution


I don't think it can be solved as most of the equations dealing with transformers assume an ideal transformer.[/B]
 
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  • #2
Hi Xvivi,
The ratio is 5:1, just to remind that even the tronsformer isn't 100% efficient the output is yet the same, the only thing that changes is the ouput current,
You can pull out the ouput voltage, use the fact of thethe 90% efficiency to determine the input current, good luck !
 
  • #3
xvivi said:
I don't think it can be solved as most of the equations dealing with transformers assume an ideal transformer.
In your analysis here you do include an ideal transformer, then add an external resistance to it to account for its non-ideality.
 
  • #4
Work out the secondary voltage assuming an ideal transformer.
Work out the output power
Work out the input power allowing for the efficiency being 90%
Work out the input current.
 

1. What is the difference between current and voltage in a transformer?

The current in a transformer refers to the flow of electrical charge, while voltage refers to the potential difference between two points. In a transformer, the current is induced by the changing magnetic field, while the voltage is induced by the changing magnetic flux.

2. How does a transformer change the current and voltage?

A transformer works on the principle of electromagnetic induction. It has two coils, a primary coil and a secondary coil, which are wound around a core. When an alternating current is passed through the primary coil, it creates a changing magnetic field, which induces a current in the secondary coil. The ratio of the number of turns in the primary and secondary coils determines the change in current and voltage.

3. Why is a transformer used in the electrical grid?

A transformer is used in the electrical grid to step up or step down the voltage levels. This is necessary for efficient transmission and distribution of electricity. High voltage is used for long-distance transmission to reduce energy loss, while lower voltage is used for safe distribution to homes and businesses.

4. What is the efficiency of a transformer?

The efficiency of a transformer is the ratio of the output power to the input power. Ideally, a transformer should have 100% efficiency, but due to losses in the form of heat and electromagnetic radiation, the efficiency is usually around 95-99%. The efficiency of a transformer can be improved by using high-quality materials and proper design.

5. Can a transformer change DC (direct current) to AC (alternating current) or vice versa?

No, a transformer can only change the voltage and current of an AC power supply. It cannot convert DC to AC or vice versa. For this purpose, other devices such as inverters or rectifiers are used.

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