why we are giving D.C. supply to field of an alternator, why can't we give the a.C. supply

Answer Posted / y.srinath

dynamically induced e.m.f requires fixed polarity& magnetic flux .if we given a.c to field the polarity of a particular pole is not fixed .if one pole behaves as north pole for +ve half cycle & same behaves as north pole for negative half cycle to.that's why we are using d.c supply for alternator.

Is This Answer Correct ?    1 Yes 1 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

why we get 2 differnet values for power factor in 2 watt meter method in 3 phase

1367


How do we arrive at selecting reactive capacitance value as 30% of h.p rating of motor?

1370


We are preparing another project which involves Waste heat recovery from a 1 MW GE Engine. The Engine in particular gives out flue gas at 487Deg C with a flow rate of 5650 kg/hour and this can be cooled to 180 Deg C. This gives a thermal output of ~ 594 KW that is available for input to VAM via heat exchanger / boiler. Additionally 581 KW will be available from engine jacket water (temperature profile 80/ 80 Deg C and a flow rate of 50m3/hr) Our estimation is that 300 TR of cooling is possible with a suitable VAM machine(s). Please advise what is the most suitable arrangement with maximum TR and min Capital expenditure. plz reply me as early as possible

1492


A commercial Building is designed with 14th floor levels with indoor substation of three phase transformer with rated capacity of 1000 Kva.The transformer delivered 65% of its rated capacity at 0.67 power factor lagging.Because of low power factor, the power customer was penalized and certain cost was charged accordingly based on every point percentage lower than 85%.This situation may repeatedly happen on the succeding energy bills of power customer.The power customer is desired to improve its historical power factor of 0.67 lagging and no further penalty be impose by the local power company on the next bill. Q: Identify the appropriate solution you want to offer to Client?.Justify SCIENTIFICALLY and MATHEMATICALLY the principles behind the solution.

1338


why 3 phase is converted into 2 phase using electronics circuit why not 2 phases are diresctly putted from the 3 phase transformer??

1676






how to calculation increase capacitor,increase power factor for three phase.

1630


Write the analogous electrical elements in force current analogy for the elements of mechanical translational system.

754


In our factory so many iron pillors are exists for supporting the shed/Hangar. If do more no of earthings at one piller instead of doing more earth pits in many locations and running earth strip around the hanger, I can save the money. Please suggest this method is acceptable as per Is specifications though the Earth resitance of the farthest piller is with in the limits as per IS specifications.

1643


What is the effect of pi controller on the system performance?

609


difference between Ac and Dc mcb ????

1121


What is the significance of integral controller and derivative controller in a pid controller?

629


How is operate breaker failure scheme in substation

1528


What is the magnetic field (coil DC ) of Turbo Expander?

1579


Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close?

675


what happen if the supply is given to the stator of the 3phase induction motor with out assembling the rotor ?

1478