Calculation and design of common power transformers with single phase less than 500W

Many electronic amateurs like to test their own circuit debugging equipment, often encounter the circuit to try, the transformer does not know how to do? Reading books, checking the information on the Internet, a lot of formulas to see dizziness, or do not know how to design a transformer. Here to guide you how to calculate and design a single-phase 500W internal power transformer.

Tools/raw materials

Calculator, silicon steel sheet specification sheet, transformer skeleton specification sheet, enameled wire specification sheet, silicon steel sheet material 470 or 600 IE type

Step / method

1, calculate the power of the transformer

Transformer power = output voltage X output current

For example, a transformer with an output voltage of 30V and a current of 10A according to the circuit requirements, 30V X 10A = 300W (transformer power)

2. Calculate the cross-sectional area of ​​the core of the transformer

Transformer power X 1.44 = Y , Y open root X 1.06 = core cross-sectional area

Transformer power 300W X 1.44 = 432,432 open root X 1.06 = 22.00 square centimeter (core cross-sectional area)

22 square centimeters = 2200 square millimeters (core cross-sectional area)

3, calculate the transformer core stack thickness

Core cross-sectional area (mm 2 ) / 矽 steel sheet tongue width (mm) = core stack thickness

2200 mm 2 / 40 mm = 55 mm (stack thickness), the core size is a silicon steel sheet with a tongue width of 40 and a stack thickness of 55 mm.

There is a problem here. Some people will ask why you can use 40 pieces of silicon steel to teach you an experience value.

Stack thickness / tongue width = (1.0∽1.6), 55mm / 40mm = 1.375.

Less than 1.0 with a small one size steel sheet, indicating that the sheet steel window is too large to be dissatisfied; greater than 1.6 with the larger size of the sheet steel, indicating that the sheet steel window is too small to wind. The specific specifications are compared with the specifications of the silicon steel sheet.

4, the choice of skeleton

The core cross-sectional area is E40 X 55, then the skeleton is E40 X 55. Compared with the transformer skeleton specification table, there is just the skeleton of this specification. If it is not, it is OK to choose the stack thickness and the larger one. If amateurs are inconvenient to buy a skeleton, then do it yourself.

5, calculate the number of coil input primary turns

45 / core cross-sectional area (cm 2 ) X 220V = input primary turns,

(45/22 cm 2 ) X 220 = 450 匝 (enter primary number of turns)

6, calculate the number of secondary turns of the coil output

(Input primary turns / 220) X output voltage = output secondary turns

(450/220) X 30V = 61.36 (take the integer 62匝)

7. Calculate the winding diameter of the enameled wire 　

Current (open root) X 0.7 = wire diameter

Output current 10A (opening) X 0.7 = 2.21 (output 30V wire diameter), input current = (300W transformer power / 220V input voltage) open root X 0.7 = 0.81 (input 220V wire diameter).

8, calculation results

矽Steel sheet specifications E40mm, stack thickness 55mm; transformer skeleton specification E40 X 55; input coil number 450匝, wire diameter 0.81 copper enameled wire; output coil number 62匝, wire diameter 2.21 copper enameled wire.

Precautions

Here mainly for electronic amateurs, the calculation method of the transformer is only suitable for small power supply transformers, and is made of EI iron core. At the same time, the circuit requirements are different, and the design requirements for the transformer are different. Please treat them differently. Due to different materials, the high-power transformers have different winding processes and different transformer structures. The design method is of course different. It will not be described in detail here.

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