Basic Electrical Engineering Interview Question Answers

•  what is electrical engineering

Electrical Engineering the field of Engineering that generally deals with the study and application of electricity, electronics, and electromagnetism.Electrical engineering deals with high voltage especially AC above the range of 110 or 220V. Moreover, electrical components and devices use alternating current (AC) / Voltages and tend to be larger in size and require 230V (In UK) and 110V (In US) single-phase ac voltages whereas in industries and power stations, it may be up to 11kV and for transmission, it may be higher than 400kV.

•  what is an ideal transformer

A ideal transformer is an imaginary transformer in which no losses occur at all. In other words, the transformer Input power is equal to the output power of the transformer i.e. they have 100% efficiency. It is just a theoretical transformer because there must be some losses in a real transformer.

Transformer input Power = Transformer Output Power.

PIN = POUT.

• Why Transformer in rated in KVA, not in kilowatt

When manufacturers design a transformer, they have no idea which kind of load will be connected to the transformer. The load may be resistive (R), inductive (L), capacitive (C) or mixed load (R, L, and C). Its mean, there would be different power factor at the secondary (load) side. The output of real power may vary depending on the power factor. Thus the manufacturer denotes it as “this transformer can provide x number of amperes at y amount of voltage”. This way, they go for VA as in (voltage x Amperes) instead of W in case of  rating of transformer.

•  what are Transformer losses and their types

A real transformer has the following losses

• Copper Losses (Winding Resistance)

The losses occur due to the current flow through the windings that causes resistive heating of the conductors.

• Core or Iron Losses

There are two types of core or iron losses

• • Hysteresis Losses

These losses occur due to the magnetic field reversal. The magnetization & demagnetization of the core consumes some energy, also known as hysteresis loss.

• • Eddy Current Losses

The losses due to the current generated inside the core. The eddy current causes the resistive heating of the core.

Various other losses include:

• Stray losses (leakage Flux)
• Dielectric Loss
• Other Losses
  • Magnetostriction Losses
  • Mechanical losses

 

• what is voltage regulation of transformer

Voltage regulation in transformer is the percentage change in the secondary voltage from no load to full load condition. Ideally, the secondary voltage remains the same throughout the load, in which case the voltage regulation is zero. But practically it varies with the power factor of the load.