Denken Exam · Free practical tool

Ideal transformer calculator

Relate winding turns to voltage and inverse current ratios. State the known winding side so the transformation direction is unambiguous.

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The method

Vp/Vs = Np/Ns = Is/Ip; ideal input power equals output power.

Before using the result

  • Ideal transformer ratios only. Input voltage/current belong to the selected known side. Regulation, losses, saturation and safety ratings are excluded.

Worked examples

These original training examples illustrate the method for Third-Class Electric Chief Engineer 電験三種 (Theory/Power/Machine/Law). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.

1. Worked example

Relate winding turns to voltage and inverse current ratios. State the known winding side so the transformation direction is unambiguous.

Primary turns
1,000
Secondary turns
100
Known side
Primary
Voltage (V)
230
Current (A)
10
  1. a = 1000 / 100 = 10.
  2. Vp/Vs = 230/23 = a; Is/Ip = 100/10 = a.
  • Primary/secondary turns ratio: 10
  • Primary voltage: 230 V
  • Secondary voltage: 23 V
  • Primary current: 10 A
  • Secondary current: 100 A

2. Comparison example

Compare a different supplied condition using the same method. For Denken Exam, the important check is that the input meaning, units and method assumptions still match the problem.

Primary turns
1,000
Secondary turns
200
Known side
Primary
Voltage (V)
230
Current (A)
10
  1. a = 1000 / 200 = 5.
  2. Vp/Vs = 230/46 = a; Is/Ip = 50/10 = a.
  • Primary/secondary turns ratio: 5
  • Primary voltage: 230 V
  • Secondary voltage: 46 V
  • Primary current: 10 A
  • Secondary current: 50 A

Check your understanding

1. Which relationship is used?

Vp/Vs = Np/Ns = Is/Ip; ideal input power equals output power.

2. Which assumption should you check first?

Ideal transformer ratios only. Input voltage/current belong to the selected known side. Regulation, losses, saturation and safety ratings are excluded.

3. How should you verify a different unit system?

Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.

Continue with the matching exam topic

This tool connects to Third-Class Electric Chief Engineer 電験三種 (Theory/Power/Machine/Law) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.

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