Definition – Frequency is the rate at which something occurs over a particular period of time. For example, when a voltage completes one cycle per second, then the frequency is 1 Hz; 50 cycles per second equals 50 Hz. It is measured in Hz (Hertz)

In India, 50 Hz frequency is used for AC electrical system that is why all our electrical equipment including generators, motors, and lights are designed to operate on 50 Hz supply. Generators are designed to produce 50Hz voltage & electrical equipments are designed to work on 50 Hz.

Effect of frequency in electrical system –

it’s a general practice that when any country uses 50 Hz frequency, they use 230V supply and those countries use 60 Hz tend to use 120 V. Frequency directly affects the performance of lights & equipment.For example-

a)if 50 Hz designed bulb is operated  on  low frequency current, the filament cools on each half-cycle of the alternating current, leading to perceptible change in brightness and flicker of the lamps; the effect is more pronounced with arc lamps, and the later mercury-vapour and fluorescent lamps.

1. b) The speed of an Induction Motor is directly proportional to the frequency of supply. When frequency is high the motor speed will be high &vice- versa.

The frequency of electrical system can affect the performance of electrical equipment which can be seen by equations given below –

f = N X P /120 – For generator voltage N = 120f/p – for motor speed

E = 4.44 Øm f N – for transformer emf

Where f = frequency, N = Speed of Generator/Motor/ turns in transformer, P = No of poles, Øm = Maximum flux.From above equations it is clear that frequency plays an important role in electrical system so it should always be in the range.