What is Transformer and How does it work?

A transformer is an electrical device that converts alternating current from one voltage to another. There are two types of transformer 'high-step' (step up) or 'low-step' (step down) and it works according to the principle of magnetic induction. A transformer has no moving/rotating parts, it is a completely stationary device. Its construction is very simple, two or more insulated copper wires wrapped around an insulated steel or iron core (laminated steel/iron core).

What is Transformer and How does it work?

A transformer has two windings, primary and secondary winding. When the primary winding supplies voltage, a magnetic field is created and the magnetic flux travels through the iron core to the secondary winding, where the magnetic field is created. As a result of which a voltage is found in the secondary coil. The rate of change of the transformer's voltage depends on the rate of five numbers of the primary and secondary coils.

What is Tap and when is it used?

Tap is provided in some high voltage transformers to correct the high or low voltage condition and output the specified voltage at the secondary terminal. Taps are set to take into account the high or low voltage, usually one and a half to one, and five percent above or below the specified primary voltage. For example: If a transformer is rated at 480 volts on the primary and operates at a line voltage of 504 volts, the tap on the primary must be 5% higher than normal to maintain the correct voltage rating at the secondary.

What is the difference between an insulating, isolating and shielded winding transformer?

Insulating and isolating transformers are the same. Basically these two terms are used for the purpose of describing the isolation of the primary and secondary windings of the transformer (isolation) or the insulation of both. Shielded winding transformers are designed with a metal shield between the primary and secondary windings to reduce noise. All two, three and four winding transformers are of insulating or isolating type. Only the primary and secondary windings of an auto-transformer are electrically connected to each other, there is no insulator or isolator.

Can a transformer be operated at a voltage other than that given on the nameplate of the transformer?

In some cases the transformer may be operated at a voltage lower than the voltage specified on the nameplate. If taps are not available, the transformer should not be operated at a voltage higher than that given on the nameplate. If the transformer is operated at a voltage lower than the rated voltage, its kVA rating will also gradually decrease. For example, if a transformer has a primary voltage of 480 volts and a secondary voltage of 240 volts, and if it is operated at 240 volts, the secondary voltage will drop to 120 volts. If the transformer is rated 10 kVA then it will be 5 kVA or proportional to the given voltage.

Why is the efficiency of a transformer high?

Transformer is a static device i.e. fixed device. It has no rotating parts, so there is no friction. The loss in transformer is very less as compared to other rotating equipment. Hence the efficiency of the transformer is very high. Transformer efficiency ranges from 95%-98%.

Can transformers be connected in parallel?

Single phase transformers can be used in parallel, but their impedance and voltage must be equal. If the voltages of the two transformers are not the same, the circulating current in the closed network of the two transformers will generate excessive heat and reduce the life of the transformer. Also the impedance of each transformer should be within 7.5%. For example: If the impedance of transformer A is 4% and transformer B is connected in parallel, then the impedance of B should be between 3.5% or 4%. Similar precautions should be taken in parallel connection of three phase transformer. Also the phase and phase angle of the two transformers should be same.