Why are transformers rated in KVA?

Transformers are rated in kVA or VA and not in kilowatts. While electric loads such as motors, lamps, heaters, etc. are always rated in kW, equipment used for power generation and transmission (generators and transformers) are rated in kVA. This article illustrates why are transformers rated in kVA and why not it is rated in … Read more

Transformer FAQ and Transformer Interview Questions

Here are the most frequently asked transformer interview questions and their answers What is a transformer? By definition, a transformer is a static electrical device that transforms electric energy from one level to another level. Normally transformers are used to step up or step down voltage and current levels, impendence matching and providing electrical isolation … Read more

Buchholz relay – Working Principle, Construction and Operation

A Buchholz relay in a transformer is an oil-activated relay, used to sense abnormalities such as short circuits, overheating, and oil leakages inside a transformer. It is a cylindrical object found in the pipe connecting the conservator to the main tank, in large oil-immersed transformers. It is very common in all oil-immersed transformers rated higher … Read more

What is meant by stalling of motor?

Motor stalling is a condition in which a motor stops rotating even when there is sufficient voltage at its terminals. This condition occurs when the torque required by the load is more than the maximum torque (Breakdown torque) that can be generated by the motor. At this condition, the motor drains the maximum current and … Read more

Types and comparison of induction motor starters

As the name indicates, starters are used to start or stop a motor. It consists of an electromechanical switch and protection devices (overload and/or short-circuit protection). Why should we need a starter? An induction motor draws 5-10 times its rated current during start. In order to reduce the starting current, we need a starter. If … Read more

What will happen if a DC voltage is applied to a transformer coil?

This is a quite common question asked by many. In fact, it is necessary to know why we don’t apply DC voltage to a transformer coil. You may come across the same question during interviews too. This article can help you clear your query.  Well! Here is the answer: Before explaining what will happen if a … Read more

Which is the most efficient electrical machine?

The most efficient electrical machine is the transformer. Transformers have efficiency above 95%. The autotransformer has an efficiency of close to 98%. The maximum efficiency is achieved under the fully loaded condition. Read More about Transformer: Electric Transformer

Operation of generators

The generator is a device which converts the mechanical energy into electrical energy.


GeneratorIn order to understand the operation of a simple generator, consider rectangular coil ABCD placed in a magnetic field as shown in the figure. The two ends of the coil are connected to the two copper half rings (or split rings) R1 and R2 called commutator. There are two carbon brushes B1 and B2 which press lightly against the two half rings.

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