ELECTRICAL EASY

For better understanding of advantages and disadvantages of Short-pitched winding, we shall first understand the meaning of short-pitched coil and full-pitched coil. It will take some 10 minutes of your precious time to go through the write-up but it will really help you. Full Pitch Coil: A full pitched coil is defined as the coil whose two coil sides are 180 electrical degree apart. As the Pole Pitch, which is defined as the space electrical angle between two consecutive poles is 180 degree, therefore in an alternate manner we can also say that a Full Pitch Coil has its two coil sides one pole pitch apart. This can be seen in the figure below. Short Pitch / Chorded Coil: If it happens that the two coil sides are not lying under the pole, then obviously the space electrical angle between the coil sides will not be 180 degree rather it will be less than 180 degree as shown in figure below. Thus we can define a Short Pitch Coil as the coil having th...

In principle, of course transmission lines can be rated in kW. There is some upper limit as to the power they can transmit. If the Power exceeds that power level then the lines would overheat, leading to breakdown of insulation and perhaps to the lines melting. But such a method of rating is pretty impractical. ( Why impractical?) The kW or MW load on a transmission line varies, literally from one instant to the next. Any rating of maximum sustained load could be exceeded on an instantaneous basis, or even for a short time, without causing too serious damage to the system though perhaps weakening it for the future. So there could be an instantaneous current spike perhaps several times higher than the rated steady-state current. So instead Power Grids are rated by voltage, which is essentially constant throughout the system. Because the limiting factor for most transmission lines is the insulation withstand voltage, the insulator size and materials and the air spacing be...

Hydrogen is used for the cooling of Rotor winding i.e. field winding and Rotor Core in Turbo Generator. As shown in figure below, there are small windows on the Rotor structure which allows the passage of Hydrogen. This hydrogen cools the Rotor structure and filed winding. This hydrogen after cooling becomes hot which in turn is cooled by a Heat Exchanger having water in tube tube side.   The use of Hydrogen for cooling of Generator Rotor has many advantages as listed below. Hydrogen is used as the cooling medium in Turbo Generators due to its high thermal conductivity. Hydrogen reduces the amount of wind resistance and friction on the spinning generator shaft, thus increasing the generator’s efficiency. A reduction in hydrogen purity from 98 to 95% on a large generator can increase losses from friction and windage by 32%; this is equivalent to 685 KW (0.7MW) for a 900 MW Generator. Hydrogen’s density at 98% purity is of the order of 1/10 that of air at a ...

The Indian Electrical Industry is one of the leading electrical markets in the world, involved in the manufacturing and development of electrical  equipment . The electrical industry consist of production of transformers, motors, generators, switch gears, home appliances, transmission lines, etc. This post describes about the top 8 Electrical Companies in India: 1. BHARAT HEAVY ELECTRICALS LIMITED (BHEL) Bharat Heavy Electricals Limited (BHEL) is the leading electrical company in India, which came into existence in the year 1964. Headquartered in New Delhi, the company is involved in the designing, manufacturing and installing of products related to power and transmission sector. BHEL is a Maharatna Company with operations in more than 70 countries in the world. Some of its products are Boilers, Transformers, Gas Turbines, Fuel Cells and Valves. 2. SIEMENS A German Multinational Corporation, Siemens is next electrical company on this list, which...

Before going to the mark difference between Dry Type Transformer and Oil Filled Transformer, it is worth to have some discussion on Dry Type Transformer. Dry Type Transformer: Dry Type Transformers find use in locations where the use oil Filled Transformers increases the fire hazard such as shopping malls, Hospitals, residential complexes etc. In dry type transformers air is used as the cooling medium instead of oil. The insulation used in dry type transformers are designed to withstand higher temperatures. Dry type transformers are more expensive than conventional transformers. Vacuum Pressure Impregnation, Epoxy Resin cast are some of the methods of Insulation adopted in Dry Type Transformer construction. Comparison between Dry Type and Oil Filled Transformer: Dry Type Transformers use air as the cooling medium. Oil Type Transformers are considered a potential fire and safety hazard for indoor application. Dry Type Transformers can be located cl...

Transformer Oil is basically an Insulating Oil. Insulating Oils or Transformer Oils are mineral electrical insulating oils processed from fractional distillation and treatment of crude petroleum.  An Insulating Oil must have the following properties: 1)    Excellent dielectric properties resulting in minimum power loss. 2)    High resistivity leading to better insulation values between windings. 3)    High flash point and thermal stability facilitating reduction in evaporation losses. 4)    Long life performance and excellent ageing characteristics, even under severe electrical stress. 5)    Virtually devoid of corrosive sulphur, leading to enhanced stability and protection against corrosion. 6)    Wider operating temperature range, resulting from higher flash and lower pour point. 7)    Available in a wide range of grades to fit every requirement and meeting every possible specific...

As we know, both Snubber Circuit and Crowbar Circuit is used for protection against Overvoltage using Thyristor but they way they protect the Thyristor has some difference. Crowbar Circuit: Power supplies are normally reliable, but if they fail then they can cause significant damage to the circuitry they supply. To protect against this it is possible to add a simple SCR overvoltage crowbar protection circuit. Crowbar protection is a fail-safe protection mechanism which short circuits the output of a power supply under failure conditions such as over voltage. Here Fail-Safe means, in case of failure the system will go to safe condition. Crowbar protection can also refer to a circuit which has its sole purpose to cause a fuse to blow by subjecting it to high current. Figure below shows a typical Crowbar Circuit. Above Crowbar Circuit uses an 8V supply and has its overvoltage protection set at 9.1V but this overvoltage setting can be adjusted by changing to the zene...