WORLD ELECTRICAL PORTAL

DOL Starter (Direct On Line Starter) Diagram & Working Principle What is DOL Starter? A DOL starter (or Direct On Line starter or across the line starter ) is a method of starting of a 3 phase induction motor . In DOL Starter an induction motor is connected directly across its 3-phase supply, and the DOL starter applies the full line voltage to the motor terminals. Despite this direct connection, no harm is done to the motor . A DOL motor starter contains protection devices, and in some cases, condition monitoring. A wiring diagram of a DOL starter is shown below: Since the DOL starter connects the motor directly to the main supply line, the motor draws a very high inrush current compared to the full load current of the motor (up to 5-8 times higher). The value of this large current decreases as the motor reaches its rated speed. A direct  online starter can only be used if the high inrush current of the motor does not cause an excessive voltage drop in the supply circuit. If

LIGHTNING ARRESTER Defination:   The device which is used for the protection of the equipment at the substations against travelling waves, such type of device is called lightning arrester or surge diverter. In other words, lightning arrester diverts the abnormals high voltage to the ground without affecting the continuity of supply. It is connected between the line and earth, i.e., in parallel with the equipment to be protected at the substation. The following are the damages that are caused by the travelling wave on the substation equipment.   The high peak or crest voltage of the surge may cause flash-over in the internal winding thereby spoil the winding insulation. The steep wave fronts of the surges may cause external flashover between the terminal of the transformer. The highest peak voltage of the surge may cause external flashover, between the terminal of the electrical equipment which may result in damage to the insulator. WORKING PRINCIPLE: Lightning arrestor working principl

SURGE ARRESTER On the flow of current in a power line increases at some point, then electrical surges will occur. The most popular surge can be occurred due to lightning because sometimes lightning can cause an electrical surge. Throughout a lightning storm, lightning may hit somewhere close to a power source and affect the voltage supply during a  power  line. Sometimes, an electrical device can be protected from the lightning surge effects by detaching it from the source of power. A surge arrester cannot work perfectly due to very high voltage which is generated from lighting. What is Surge Arrester? Definition :  A protective device that is used to protect the electrical  power system  from surges caused by lightning is known as surge arrester. It includes two terminals like high voltage and ground. Once an electric surge travels through the surge arrester from the power system, then a huge voltage current can travel to the insulation directly otherwise to the ground terminal to pro

POWER FACTOR CORRECTION- complete guide. What is power factor? Power factor is a measurement of power quality and can be calculated in relation to an entire power system or individual equipment such as low voltage switchgear. The formula for power factor is PF = kW / KVA. The above formula calculates the ratio of working or actual power (kW) to the apparent power; which is what we are charged for (kVA). So, in basic terms power factor is a calculation of how much value for money we’re getting for the power we truly consume. The excess power supplied but which doesn’t produce any productive work is known as the reactive power (kVAR). The reactive power (kVAR) and actual power (kW) combined will amount to the total apparent power. A perfect power factor is 1.0, which would signify complete value for money, where zero reactive power is present, and all power is being used productively. However, a perfect power factor is typically unfeasible to achieve, and it is more realistic to aim for

How Does a Generator Create Electricity? How Generators Work Generators are usefull appliances that supply electrical power during a power outage and prevent discontinuity of daily activities or disruption of business operations. Generators are available in different electrical and physical configurations for use in different applications. In the following sections, we will look at how a generator functions, the main components of a generator, and how a generator operates as a secondary source of electrical power in residential and industrial applications. How does a generator work? An electric generator is a device that converts mechanical energy obtained from an external source into electrical energy as the output. It is important to understand that a generator does not actually ‘create’ electrical energy. Instead, it uses the mechanical energy supplied to it to force the movement of electric charges present in the wire of its windings through an external electric circuit. This flow

Why Transformer Rated In kVA, Not in KW? Transformer Always Rated In kVA instead of KW As the name suggest,  transformer  only transfer the power from one circuit to another without changing the value of power and frequency. In other words, It can only step up or step down the value of  current and voltage  while the power and frequency would remain same. A general  date on transformer nameplate  are printed for further details, such as rating in VA, single phase / three phase ( power or distribution transformer ), step up / step down, connection etc. Right to the question, In simple words, There are  two type of  losses in a transformer ; 1 )   Copper Losses 2)   Iron Losses or Core Losses or Insulation Losses Copper losses (I²R)   depends on   current  which passing through transformer winding while  Iron losses or core losses or  Insulation losses depends on Voltage . i.e. total losses depends on voltage (V) and current (I) which expressed in  Volt ampere  ( VA ) and not on the loa