Electronics Homework

Electronic Class





Counting and assemble the transformer for power supply  in home lab.


Transformer is very important part of power supply. It allow to transform the AC voltage without loosing energy. Efficiency of transformer is 95 - 98%. The weaknesses of transformer is big weight, coast, and technologies problems with assembling.


Counting the transformer. 


Given:          V1 - primary AC voltage 50-60 Hz  (~120 V);

                    V2 - secondary AC voltage;

                    I2 - secondary current;


1)       The power (P) of transformer: P = V1 x I1 = V2 x I2;

So I1 = V2 I2 /V1

2)       The area (cm2) for window of the coil = a x b. Approximately we can find it like P . So size a and b of the core = P . 

3)       Transformer core is the set of iron’s slices (picture 1). Find in Data Book the size of transformer core b = a (cm)   bigger and closest to P  .  The quantity of the pieces n = a/d, where d is width of one piece.

4)       Find the quantity of the loops per one volt M. Use the empirical formula: M = 50/P . So quantity of the loops for primary coil of transformer: w1 = V1 x M . For secondary coil do same way:  w2 = V2 x M.

5)       Diameter of wires in millimeters we can find from the formula: d = .02 x I  . So for primary coil d1 =  .02 x I1  and for secondary coil d2 =  .02 x I2  (mm).


Assembling the transformer.


1)       Making the bobbin for the transformer coil with the carton and glue and sizes of the core (picture 2).

2)       Round the first coil on bobbin with wire d1  and quantity loops are w1 (picture 3).

3)       Round the second coil on bobbin with wire d2  and quantity loops are w2 (picture 4, 5).

4)       Setup the iron’s slices of transformer core in the bobbin (picture 6 & 7).

Fig. 1


Fig. 2


Fig. 3


Fig. 4


Fig. 5


Fig. 6


Fig. 7



Study name and pictures of the details above


I recommend to use online book about electronics: http://www.learningelectronics.net/