TRANSFORMER

Transformers
     What is transformer?.
     A transformer is a device that is use to step-up or to step-down the voltage in the source. Transformers is composed mainly of two or more wires that is not connected, wound in a metallic object such as iron. Picture below is one examples of commonly used transformers in many of our appliance. The second picture below is the transformers used in the distribution in transmission lines.

Appliace Transformer

Distribution Transformers

Those big and small transformers has the same function, either to step-up or to step-down voltages.

What is inside the transformer?
     For common appliance transformer, inside is two unconnected wires. Wires are not connected in actual, but they are connected magnetically. What will happened in the primary winding will be felt by the secondary winding. The voltage in either winding is equal                                       

                                                         V = Ndf/dt

where:

V= is the voltage in the winding

N= is the number of turns in winding
df/dt= is the rate of change in magnetic flux with respect to time

http://en.wikipedia.org

We can also say that the voltage in the primary winding is proportional to the voltage in the secondary winding by a factor of  N1/N2, where N1 and N2 is the the number of turns in the primary and secondary windings respectively. The voltage and number of turns ration is constant.

                                                    N1/V1=N2/V2 = C
 For the current relation in the transformer, if the transformer is a step-down transformer, the current increase by a constant. This constant is equql to the ratio of the primary and secondary voltage.

                                                           V1I1=V2I2

                                            or

                                                          I1/I2=V2/V1

For A Three Phase Transformers
     For a three phase transformers, the output voltage in its output has the same magnitude but different in phase angle. The current also if assumed a balance load has the same magnitude but different int phase angles. The phase angle diffenrences for the voltage is 120degrees and for the current if assumed a balance load is equal to 120 degrees. The current in phase angle and magnitude differs if the load in not balance.
Unbalance load means that the load in phase A, differs with that of phase B, and differs with phase C or vise versa. Three phase transformers are commonly used in machines that require large amount of power since three phase tranformer supplies 3times that of the single phase.