How to work out the turn ratio on a transformer

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Discussion Overview

The discussion revolves around calculating the turn ratio of a transformer using input and output voltages. It includes theoretical considerations, practical implications, and various types of transformers.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant suggests that for an ideal transformer, the turns ratio can be calculated using the formula N = Vp/Vs, where Vp is the primary voltage and Vs is the secondary voltage.
  • Another participant notes that in real transformers, the turns ratio may be slightly higher than calculated, typically by about 2%, and suggests using a primary voltage that is about 10% of the rated voltage for improved accuracy.
  • Several participants provide examples of calculating the turns ratio, with one stating a ratio of 24.6 based on specific voltage values.
  • There is a discussion about the types of transformers, with one participant mentioning that step-up transformers have a turns ratio greater than 1, while step-down transformers have a ratio less than 1. Another participant adds that there are more types of transformers beyond just these two categories.
  • Multiple participants inquire about calculating the output voltage of a transformer based on the input voltage, indicating a need for clarification on the relationship between voltage and turns ratio.
  • One participant mentions that the formula for calculating the turns ratio is provided in an earlier post but emphasizes that one can only solve for one unknown with one equation, suggesting the need for measurements if the turns ratio is unknown.

Areas of Agreement / Disagreement

Participants express differing views on the calculation of the turns ratio, with some providing examples that lead to confusion regarding the correct representation. There is no consensus on the specific values or methods for calculating the output voltage based on the input voltage.

Contextual Notes

Some participants highlight that the calculations depend on ideal versus real transformer conditions, and there are unresolved questions about the specific formulas and their applications in different transformer types.

speedy46
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I would like to know how to work out the turn ratio on a transformer from having just the input and output voltages.
 
Last edited:
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For an ideal transformer (that is, no losses in the windings or in the core), the turns ratio is just N = Vp/Vs where
N = turns ratio
Vp = primary Voltage (rms)
Vs = secondary Voltage (rms)

In real transformers, the turns ratio will be slightly higher (typically about 2%) than what is calculated by this formula. One way to improve the accuracy of the calculation is to use a primary Voltage that is only about 10% of the rated Voltage.
 
For example = 244 / 9.88 = 24.6

So the turn ratio is 24 - 6
 
Last edited:
There are two types of transformers,step-up transformer(sut) and step-down transformer(sdt),the turns ratio for (sut)is bigger than 1 and for (sdt) is less than 1.
 
speedy46 said:
For example = 244 / 9.88 = 24.6

So the turn ratio is 24 - 6

what? isn't it 246 to 10? or 24.6 to 1?
 
ws0619 said:
There are two types of transformers,step-up transformer(sut) and step-down transformer(sdt),the turns ratio for (sut)is bigger than 1 and for (sdt) is less than 1.

There are quite a few more types of transformers than just step-up and step-down (e.g. autotransformers, buck-boost, isolation).

CS
 
Thank you

How do you calculate the out put voltage of a transformer when you only know the input voltage
 
speedy46 said:
Thank you

How do you calculate the out put voltage of a transformer when you only know the input voltage

its based on the ratio as stated
 
Is there a formula for working this out please
 
  • #11
The formula is in post #2. But, you can only solve for one unknown when you have only one equation. If you don't know the turns ratio, you must measure the primary and secondary Voltages.
 
  • #12
thank you
 

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