Why Are Primary Turns Fewer and Thicker in Step-Up Transformers?

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Discussion Overview

The discussion revolves around the design characteristics of step-up transformers, specifically focusing on the number of turns in the primary and secondary coils, the thickness of the wire used, and the relationship between voltage and current. Participants explore the underlying principles of transformer operation, including frequency considerations and practical applications.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants suggest that fewer turns in the primary coil result in lower voltage and higher current, necessitating thicker wires.
  • Others argue that the frequency of the A.C. voltage in the secondary coil must match that of the primary, questioning why there is confusion about this.
  • One participant proposes that more turns in the secondary coil lead to higher voltage, indicating a proportional relationship between turns and voltage.
  • There is a discussion about the relationship between resistance and voltage, with some participants questioning if increased turns imply increased resistance and thus higher voltage according to Ohm's law.
  • A participant introduces the application of step-up transformers in switch mode power supplies (SMPS), highlighting their efficiency and design differences compared to traditional transformers.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the frequency of the voltage in transformers, with some agreeing that it remains constant while others seek clarification. There is no consensus on the implications of resistance in relation to turns and voltage.

Contextual Notes

Some participants express confusion about the frequency of the voltage in transformers, indicating a potential misunderstanding of transformer theory. The discussion includes practical applications that may not be fully explored in theoretical contexts.

Who May Find This Useful

This discussion may be useful for individuals interested in electrical engineering, transformer design, and practical applications of transformers in power supply systems.

Hardik Batra
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WHY in step up transformer, the number of turns are less in primary and copper wire is thick. Whereas in secondary number of turns are more and copper wire is thin.

In step-down transformer the situation is reversed.

I want the reason for this?
 
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Fewer turns -> lower voltage -> higher current at the same power -> thicker cables required
 
For in step up transformer, the frequency of the A.C. Voltage induced in the secondary has the frequency as that of the voltage in primary-----confusing why?
 
Why do you expect the frequency to change?
The magnetic field oscillates with the same frequency as the coils - they cannot have a different frequency.
 
how the voltage be increase in step up transformer?
 
More turns -> higher voltage

Those two are proportional to each other.
 
Your mean that more turn --> more resistance --> from v = IR --> more voltage ?
 
Hardik Batra said:
For in step up transformer, the frequency of the A.C. Voltage induced in the secondary has the frequency as that of the voltage in primary-----confusing why?

How could it be a different frequency? 1. What possible mechanism could cause it and.
2. Which frequency would it choose to be?

What's confusing about that, if the only conclusion must be that it's the same.
 
Hardik Batra said:
Your mean that more turn --> more resistance --> from v = IR --> more voltage ?
Did you think of looking up transformers / transformer theory on Wiki? You could avoid all these odd questions by just reading about it.
 
  • #10
Step up transformers are frequently used in SMPS for audio amplifiers in cars for example. The 12V from the battery cannot deliver much energy through a 4 Ohm load. Here comes the frequency you might be wondering about. In such SMPS the DC voltage from the battery is "sliced" into pulses by some electronics. This pulsed voltage is has a frequency at several 100 kHz. Thus the transformers are small and efficient with a few turns of very thick wire at the primary side, and a thinner (But still relatively thick) wire on the secondary side. The resistance in the windings are often less than 0.001 Ohm - on both sides, even though the secondary winding might have 10 times the resistance, but still very low. These power supplies (SMPS stands for Switch Mode Power Supply) are much more efficient than 50Hz transformes which is designed to transfer as much energy as the smaller high frequency transformer.

Maybe more information than you asked for...

Vidar
 

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