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What is transformer
What is transformer
Transformer is an electrical device which able to change voltage by lowering or increasing the voltage value.
This transformer discovered from the principle of induction by Ottó Bláthy, Miksa Déri and Károly Zipernowsky (Hungarian engineers) in 1885 .
A transformer contains two coils (or winding) and conductor material is using soft iron.
The input supply or incoming supply we identify as primary coil and the supply out is known as secondary coil. The voltage coming out from the secondary coil is call induced voltage. Low voltage LV transformer are made for AC supply below 500 volts.
Transformer Principles
Transformer Principles
A transformer is a passive electrical device that transfers electrical energy between two or more circuits. A varying current in one coil of the transformer produces a varying magnetic flux, which, in turn, induces a varying electromotive force across a second coil wound around the same core.
Elements of transformer
Elements of transformer
a. Voltage (V)
Vp - voltage primary
Vs - voltage on secondary coil
b. coil winding or Turns (T)
Np - number of turns in primary coil
Ns - number of turns on secondary coil
c. current (A)
Ip - current on primary coil
Is - current on secondary coil
Transformer Formula
Transformer Formula
Formula;
Where;
Vp voltage primary winding
Vs voltage secondary winding
Np number of turns in primary coil
Ns number of turns in secondary coil
Ip current at primary
Is current at secondary coil
Step down Voltage
Step down Voltage
Figure above is identified as step down transformer. The transformer are commonly used in many electrical and electronics supply.
The primary coil can be check with the use of multi-meter (ohm range) and get the highest resistance value.
The secondary coil of a transformer are usually lower resistance value.
Step up Voltage
Step up Voltage
Figure above is known as step up transformer.
The transformer are specifically used in some electrical and electronics circuits.
The primary coil can be check with the use of multimeter (ohm range) and get the lower resistance value.
The secondary coil of a transformer are usually higher resistance value.
Figure above is a single phase transformer, commonly consisting of four terminal connects which a pair of primary and secondary.
Figure above is another single phase transformer.
Common step down secondary output voltage are range of 3, 5, 12, 24 and 36 volts.
If a transformer consist another terminal normally no 5, this is identify as E for grounding the transformer body.
Types of transformer
Types of transformer
Basically types of transformer are categories:
1. Power transformer
Example of the following types are
Power,
Audio transformer,
Constant voltage transformer,
Loud speaker transformers,
Variable resistance transformer.
Toroidal (or dough nut shape)
Laminated core
2. Instrument transformer
Examples of these transformer
Resonant transformer
Current transformer
Voltage transformers
Ferrite Core
3. Communications or radio signal
Examples of these transformer can be found on any communication devices.
RF transformer,
Signal transformer ,
Video balun
Three phase transformer
Three phase transformer
Three phase transformer is basically consist of three set of winding (coil), this is commonly use for three phase supply only.
Each winding or coil of this transformer are single phase winding.
The power of both primary and secondary winding is the same with formula below.
Pp1 = Vp1 x Ip1 <=> Vs1 x Is1
Pp2 = Vp2 x Ip2 <=> Vs2 x Is2
Pp3 = Vp3 x Ip3 <=> Vs3 x Is3
Figure above showing a three phase transformer diagram.
P1 means primary winding for L1 (or Red phase).
S1 indicating secondary for L1 or sometimes labeled as A.
P2 means primary winding for L2 (or Yellow phase).
S2 indicating secondary for L2 or sometimes labeled as B.
P3 means primary winding for L3 (or Blue phase).
S3 indicating secondary for L3 or sometimes labeled as C.
All above picture is an example of three phase transformer.
Auto transformer
Auto transformer
An auto-transformer is basically a three phase transformer with tapping supply point, it is also known as auto step down transformer and named auto-trans voltage reduction device. A simple auto-transformer has only one point tapping and it is commonly selected according to design circuits of component. The terminals of an auto-transformer has 3 sets x 3 winding with total of 9 terminals overall. The label of the terminals are commonly identify 0v (star symbol) , then follow by 50% 120v and a 100% 240v terminals.
Figure above is an auto-transformer wiring diagram with tapping point to lower supply voltage.
For many tapping point the transformer is added with more terminals which indicates certain percentage of supply required. The tapping point can have range of 50%, 65%, 75% and 80%.
Figure above showing a physical auto-transformer.
Basic Transformer calculation
Basic Transformer calculation
Main formula ; Vp ÷ Vs = Np ÷ Ns = Is ÷ Ip
Example 1: Finding number of turns.
A transformer with voltage primary (Vp) is 230 volts and secondary voltage (Vs) is 130 volts, the number of turn on primary winding (Np) is 600T, find the secondary number of turns (Ns)?
Solution: Ns = Vs x Np ÷ Vp
Ns = 130v x 600T ÷ 230v = 339.13 T
Example 2: Finding current.
Given the Vp is 220 volts and Vs is 80 volts, the primary current is 3 ampere. Calculate the secondary current (Is) of the transformer?
Solution: Is = Vp x Ip ÷ Vs
Is = 220v x 3A ÷80v = 8.25 A
Example 3:
A transformer with voltage primary (Vp) is 220 volts, number of turns on primary (Np) is 500T and secondary (Ns) is 3200T. Calculate the expected voltage at secondary (Vs)?
Solution: Vs = Vp x Ns ÷ Np
Vs = 220v x 3200T÷ 500T = 1408 V
For more exercise click here.
Auto-Transformer Voltage calculation
Auto-Transformer Voltage calculation
Example
1) Calculations of the auto-transformer settings can identify.
Solution: 120v ÷ 240v x 100% = 50%
2) Given the percentage of auto-transformer setting is 65% of 415 volts, find the voltage output expected from the secondary winding?
Solution: 65% of 415 volts
= 0.65 x 415v = 269.75 volts
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