Homework
Transformer
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:
V_{1}  primary AC voltage 5060
Hz (~120 V);
V_{2}  secondary AC voltage;
I_{2}  secondary current;
1)
The power (P) of transformer: P = V_{1}
x I_{1} = V_{2} x I_{2};
So I_{1} = V_{2} I_{2}
/V_{1}
2)
The area (cm^{2}) for window of the coil
= a x b. Approximately we can find it like P^{½}
. So size a and b of the core = P^{¼} .
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^{¼
}.
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^{½} .
So quantity of the loops for primary coil of
transformer: w_{1} = V_{1} x M .
For secondary coil do same way:
w_{2} = V_{2} x M.
5)
Diameter of wires in millimeters we can find from
the formula: d = .02 x I^{½}
. So for primary
coil d_{1} =
.02 x I_{1}^{½ }
and for
secondary coil d_{2} =
.02 x I_{2}^{½}
(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 d_{1}
and quantity loops are w_{1 }(picture 3).
3)
Round the second coil on bobbin with wire d_{2}
and quantity loops are w_{2 }(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/
