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Saturday, 18 July 2015
Why do cylindrical Alternators operate with steam turbines?
Steam turbines are found to operate at fairly good efficiency only at high speeds. The high speed operation of rotors tends to increase mechanical losses and so the rotors should have a smooth external surface. Hence, smooth cylindrical type rotors with less diameter and large axial length are used for Synchronous generators driven by steam turbines with either 2 or 4 pole...
1. Why almost all large size Synchronous machines are constructed with rotating field system type?
The following are the principal advantages of the rotating field system type construction of Synchronous machines:
· The relatively small amount of power, about 2%, required for field system via slip-rings and brushes.
· For the same air gap dimensions, which is normally decided by the kVA rating, more space is available in the stator part of the machine for providing more insulation to the system of conductors, especially for machines rated for 11kV or above.
· Insulation to stationary system of conductors is not subjected to mechanical...
Friday, 17 July 2015
Generator Protection
Generator Protection
GENERATOR AND ITS PROTECTION
The
core of an electrical power system is the generator. There are power
units based on steam, gas, naphtha, water power, diesel engine drive and
wind mills. The range of size extends from a few hundred KVA (or even
less) for engine-driven and hydro sets up to turbine driven sets
exceeding 500MVA in rating.
...
Comparision of Direct-on-line (DOL) and Star-delta Motor Starting
Motor starting methods
Direct-on-line starting (DOL)
As the name suggests, direct-on-line starting means that the motor is started by connecting it directly to the supply at rated voltage. Direct-on-line starting, (DOL), is suitable for stable supplies and mechanically stiff and well-dimensioned shaft systems – and pumps qualify as examples of such systems.
Line diagram for Direct-on-line motor starting
Where:
K1 –...
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