How Do You Calculate Primary Current in a Step-Up Transformer?

In summary, the 5kVA ideal step-up transformer with a turns ratio of 200:1700 and a primary voltage of 1000V has a primary current of 5A at full load. This can also be calculated by dividing the secondary current (0.588A) by the turns ratio (10/17) and then dividing by the primary voltage (1000V).
  • #1
RRTF
1
0

Homework Statement


An 5kVA ideal step-up transformer having a turns ratio of 200:1700 and is connected to a primary voltage of 1000V. Determine the primary current at full load.

Homework Equations


Vs/Vp = Ns=Np = Ip/Is

The Attempt at a Solution


I think it is 1700/200=Vs/1000=8500V
But, I do not know how to calculate the current,
I think it is 5kVA/8500 is Secondary current
then when I have Secondary current is 10/17 (0.58823)
((10/17) x 8500) / 1000 = 5A

I think the primary current at full load is 5A?

Thank you
 
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  • #2
All sounds good to me.
Since it is ideal, 5 kVA can be used on primary or secondary:
primary 1000V x 5A or secondary 8500V x 0.588A both = 5 kVA
 
  • #3
RRTF said:

Homework Statement


An 5kVA ideal step-up transformer having a turns ratio of 200:1700 and is connected to a primary voltage of 1000V. Determine the primary current at full load.

Homework Equations


Vs/Vp = Ns=Np = Ip/Is

The Attempt at a Solution


I think it is 1700/200=Vs/1000=8500V
But, I do not know how to calculate the current,
I think it is 5kVA/8500 is Secondary current
then when I have Secondary current is 10/17 (0.58823)
((10/17) x 8500) / 1000 = 5A

I think the primary current at full load is 5A?

Thank you
Since the transformer has capability of 5000 VA and 1000V is connected to the primary, the input current is at "full load" is 5000/1000 = 5A, a quick way to your answer.
 

1. What is an ideal step-up transformer?

An ideal step-up transformer is a device that increases the voltage of an alternating current (AC) while decreasing the current, without any losses in energy. It is made up of two or more coils of wire, known as the primary and secondary windings, which are wound around a common iron core.

2. How does an ideal step-up transformer work?

An ideal step-up transformer works on the principle of electromagnetic induction. When an alternating current flows through the primary winding, it creates a changing magnetic field around the iron core. This changing magnetic field induces a voltage in the secondary winding, resulting in an increased voltage output.

3. What is the voltage ratio of an ideal step-up transformer?

The voltage ratio of an ideal step-up transformer is equal to the ratio of the number of turns in the secondary winding to the number of turns in the primary winding. For example, if the secondary winding has twice as many turns as the primary winding, the voltage ratio would be 2:1.

4. What is the purpose of using an ideal step-up transformer?

The purpose of using an ideal step-up transformer is to increase the voltage of an AC power supply. This is useful in many applications, such as in power transmission, where high voltages are needed to reduce power losses over long distances, or in electronic devices that require a higher voltage input than the available power supply.

5. Are there any limitations to ideal step-up transformers?

Yes, there are several limitations to ideal step-up transformers. They can only be used with AC power sources, and they are not able to increase the power of the input signal. Additionally, real-world transformers have losses due to factors such as resistance and leakage inductance, which means that the output voltage will not be exactly equal to the theoretical voltage ratio.

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