A 400 V , 50 Hz ,three phase alternator ,rated at 200 kVA at a lagging power factor of 0.835 , is star connected and driven at 1500 rpm. The windings of the alternator have resistance 0.01 Ω and reactance, 0.118 Ω per phase at 50 Hz. The stator of the alternator has 96 slots, with 6 conductors per slot , in a double layer. To improve the wave form only 80 % of the pole pitch is wound. The alternator can be considered to have “constant overall efficiency” of 90 %. Determine the value of the maximum pole flux available to the alternator According to available information about the alternator described above it may be used to produce 60 Hz , provided the maximum phase current is limited to the same value as when operating at 50 Hz. Determine for the alternator ,when operated at 60 Hz: smallest power factor at which the current can deliver its rated load the rated output power
Synchronous Generator
In comparison to an asynchronous generator, it is a machine where the rotor speed is equal to the rotating magnetic field produced by the stator, i.e., mechanical speed is equal to the electrical speed, thus called synchronous, and not asynchronous.
Salient Pole Rotor
Salient pole rotor includes a large number of exposed poles mounted on a magnetic wheel. The construction of a bright pole is as shown in the image on the left. The proposed poles are made of metal laminations. The rotor winding is provided on these poles and is supported by pole shoes.
A 400 V , 50 Hz ,three phase alternator ,rated at 200 kVA at a lagging power factor of 0.835 , is star connected and driven at 1500 rpm. The windings of the alternator have resistance 0.01 Ω and reactance, 0.118 Ω per phase at 50 Hz. The stator of the alternator has 96 slots, with 6 conductors per slot , in a double layer. To improve the wave form only 80 % of the pole pitch is wound. The alternator can be considered to have “constant overall efficiency” of 90 %.
Determine the value of the maximum pole flux available to the alternator
According to available information about the alternator described above it may be used to produce 60 Hz , provided the maximum phase current is limited to the same value as when operating at 50 Hz.
Determine for the alternator ,when operated at 60 Hz:
smallest power factor at which the current can deliver its rated load
the rated output power
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