VOLTAGE

VOLTAGE

1.             Static:                     The item that rubs off the outer layer of the atom “steals” some of the extra electrons, giving it a slightly negative charge. We call this built-up electric charge “static electricity.”

We rub our comb or ruler to our hair some of the electrons move to the ruler and because of that, it attracts pieces of paper.

2.             Dynamic:                              Dynamic electricity is a flow of electrical energy that occurs in a long period time. There are two types of electricity voltage.

a.       Alternating Current (AC)

b.      Direct Current (DC)                

Alternating Current (AC):

An electric current that repeatedly changes its direction or strength, usually at a certain frequency. The term is also used to describe alternating voltage. Power stations generate alternating current because it is easy to raise and lower the voltage  of such current using transformers; thus the voltage can be raised very high for transmission (high voltages lose less power as heat than do low voltages), and lowered to safe levels for domestic and industrial use.

When an alternator produces AC voltage, the voltage switches polarity over time, but does so in a very particular manner. When graphed over time, the “wave” traced by this voltage of alternating polarity from an alternator takes on a distinct shape, known as a sine wave:

An AC voltage wave than period is the rate of that back-and-forth oscillation. This is called frequency. The modern unit for frequency is the Hertz (Hz), which represents the number of wave cycles completed during one second of time. In Pakistan the power system frequency is 50 Hz, the AC voltage only completes 50 cycles every second and AC voltage is 220 Volts.

Frequency:         In AC supply, number of cycles passed through in one second is called Frequency. 

Phase:             Phase is somewhat as live wires carrying Alternating current phase means initial angle of sinusoidal signal 90,180.270 degrees or radians.

Neutral:      Neutral is a circuit conductor that carries current in normal operation, which is connected to ground (or earth).

Neutral:       In multiphase circuits, the conductor used to carry unbalanced current. In single-phase 

Conductor   systems, the conductor used for a return current path.

Ground:          An electrical term meaning to connect to the earth. 

Voltages are in three categories.

Low Voltage                            (LV)                    Less than 1000 V

Medium Voltage                      (MV)                     1kV to 33 KV

        High Voltage/Tension                    (HV/HT)                       More than 33 KV

Direct Current (D.C):

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. The electric charge flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for direct current was galvanic current.

Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements. Direct current may be made into alternating current with an inverter or a motor-generator set.

Direct current is used to charge batteries, and in nearly all electronic systems as the power supply. Very large quantities of direct-current power are used in production of aluminum and other electrochemical processes.

Direct current is used for some railway propulsion, especially in urban areas. High voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids.

Direct Current (DC)                 

The flow of electric charge is only in one direction.

DC supply we gets from;

1.       DC Generator

2.       Battery

3.       Rectifier / Diode (its a component)

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