What is transformer | transformer winding formula

The Transformer is an electrical static device, it cans Steps up & Steps Down the voltage and the current without changing the Frequency, it works only on the AC voltage it will not work on DC voltage. Its works on "Faraday's law” of “Mutual Induction" based, the voltage and current transfer from one coil to other coil with help of electromagnetic, It not have any movable part, it Current rating measure always in "KVA".

What is the Mutual Inductance?            

When two coils are placed close to each other changing the electromagnetic field produce by the current in one coil will cause to induced the voltage in the second coil because of the mutual inductance Mutual inductance is established by the inductance of each coil and by the amount of the coupling between the two coils is wound on a common core.

Why Rating in KVA?

First of that entire "KVA" means "Kilo Volt Ampere" we take a transformer rating in "VA" 'K' only use for Kilo.

Another reason that Power factor has not mattered in the transformer, it’s manufactured without consideration, that which will be load connect to this transformer.

And other reason, when any appliances consume electricity we take rating in KW, but when any appliance give power to us or transfer, we'll rating in “VA” so transformer only transfer electricity not consume.

How many types of transformer connections? 

 There are Four (4) types of connection
1-   Star to Star
2-   Delta to Delta
3-   Star to Delta
4-   Delta to Star

 How many phase will the transformer operate?

 Transformer will operate on both “Single Phase” and “Three Phase”
 Transformer Usages;

•  Generating Station.

•  Stabilizers.

•  Battery Charger/UPS etc. 

 Parts of Transformer

1- Bobbin

Bobbin used for Coil

Coil makes from enameled wire.

2- Core

There are three types of core. 
·              Air core
·              Ferrite core
·              Iron core
 "Air & ferrite core" mostly using at high frequency, and Iron core commonly used, Core uses for transfer magnetic flux."

3- Enameled Wire

Enameled wire used for windings.

4-Insulation paper

Insulation paper used to separate one coil from another coil.

5- Oil
We are use "Mineral" oil in the transformer, Oil provide culling & insulating to windings that windings will not break quickly because windings take heat when transformer on using condition.

Note: - Heat is depended on output Load.

 "Transformer having two windings"

1-   Primary Winding (Input Winding)
2-   Secondary Winding (Output Winding)

 How many types of Transformer?

There are many types of transformer some types mention here.

1- Step Up Transformer
This type transformer increase voltage from AC to AC its primary winding is lower than secondary winding, it’s used on Grid station for transfer voltage and other uses for voltage Stabilizers.

2- Step down Transformer
This type of transformer decrease voltage from “AC” to “AC”, its primary winding is higher than secondary winding; this is use for distribution electricity and other for battery charger or power supplies.

3- Auto Transformer
This type of Transformer which known as Auto/Variable transformer this is only having one winding for input and output this type transformer mostly used in voltage stabilizers its work increase or decrease voltage.

4- Isolation transformer
This type transformer mostly used for own safety purpose from shock it provide “Galvanic isolation” and highly changing of voltage its primary and secondary windings ratio is equal, its uses for power supply for sensitive equipment such as Computers, medical devices or laboratory instruments etc.

5- Power transformer
This type transformer use for both works Step Up & Step Down this used from “765Kv” to “33Kv” it use for transmission and Receiving, and its Load Fluctuations is low and always operate at Full load with 100% efficiency at full load, power transformer size is very big because it use only on Grid stations.

6- Ferrite core transformer

This type transformer use for high frequency device and very low losses, its uses in electronic applications such as switch mode power supply “SMPS” and “UPS”, its core ‘E’ shape or ‘Round’ shape core and this size very small.

7- Toroidal Core transformer

This type transformer is Round shape, Ferromagnetic Material its higher efficiency, low losses, low noise and lower operating temperature, but it cannot use for higher voltage difference it work only “40%” Step down and “115%” Step up from input voltage.

 Transformer Winding Formula for Stabilizer, Battery Charger and “UPS”.

Note:- Transformer Bobbin size take in "inch"
Formula:- 

Step 1:- Length * Width = Square Inch 

Step 2:- 8 / Square inch = Turn per volt (TPV)
Note "8" is constant value
(TPV) is Turn for one Volt.

Step 3:- TPV * Required voltage

Step 4:- Chose wire gauge 

Example:-
I want to make a transformer for battery charger I have a bobbin 1.5 inch By 2 inch
Input voltage is 230v
Output voltage for battery charger require 14.5v "20amp".

Step 1:-
Length * Width = Square Inch
1.5*2 = 3 

Step 2:- 8/Square inch = Turn per volt (TPV)
8 / 3= 2.66 
2.66 is Turn per volt (TPV) 

Step 3:- TPV * Required voltage "For Input"
2.66 * 230 = 611.8 (Round off 612)
We will give "612" turns for primary winding (Input).

Step 4:- Wire gauge depend on the current when input and output current is different because voltage is different so now we calculate the current then select wire gauge.

We know that output current is 20 amps, Like above example so we will chose Wire gauge for secondary winding easily take from Current rating Table, but wire choose for Primary winding we will do a calculation.

 Ampacity (Current) Formula

Calculation;
Note: - Primary wire gauge depended on the Secondary Load 
Formula:-

Step 1:- Current * Voltage = Watt 

Step 2:- Watt / Voltage = Current (Ampere) 
Output Current is "20amp"
Output Voltage is "14.5v" 
Put Values

Step 1:-
20 amp * 14.5v = 290 watt 

Step 2:-
Note:- We take here voltage from Primary winding.

290 watt / 230v = 1.26 Amp.

So:
Now we can take both of them wire gauges easily from Current Rating Table...

 ↓↓↓

Current Rating Table

SWG	Current	mm	Copper g/ft	Silver g/ft
1	180	7.62	124.0854	62.04268
2	152	7.01	104.878	52.43902
3	127	6.4	87.5	43.75
4	108	5.89	74.08537	37.04268
5	89.9	5.38	61.89024	30.94512
6	73.7	4.88	50.91463	25.45732
7	62	4.47	42.68293	21.34146
8	51.2	4.06	35.36585	17.68293
9	41.5	3.66	28.56707	14.28354
10	32.8	3.25	22.59146	11.29573
11	26.9	2.95	18.53659	8.341463
12	21.6	2.64	14.90854	6.708841
13	16.9	2.34	11.67683	5.254573
14	12.8	2.03	8.810976	3.964939
15	10.4	1.83	7.134146	3.210366
16	8.19	1.63	5.640244	2.53811
17	6.27	1.42	4.329268	1.948171
18	4.61	1.22	3.170732	1.426829
19	3.2	1.02	2.204268	0.991921
20	2.59	0.914	1.786585	0.803963
21	2.05	0.813	1.411585	0.635213
22	1.57	0.711	1.079268	0.485671
23	1.15	0.61	0.792683	0.356707
24	0.968	0.559	0.667683	0.300457
25	0.8	0.508	0.551829	0.248323
26	0.648	0.457	0.445122	0.178049
27	0.538	0.417	0.371951	0.14878
28	0.438	0.376	0.301829	0.120732
29	0.37	0.345	0.254878	0.101951
30	0.308	0.315	0.21189	0.084756
31	0.269	0.295	0.185366	0.074146
32	0.233	0.274	0.160671	0.064268
33	0.2	0.254	0.137805	0.055122
34	0.169	0.234	0.116768	0.046707
35	0.141	0.213	0.097256	0.038902
36	0.116	0.193	0.079573	0.031829
37	0.0925	0.173	0.06372	0.025488
38	0.072	0.152	0.049695	0.019878
39	0.0541	0.132	0.037195	0.014878
40	0.0461	0.122	0.031707	0.012683