Recent questions and answers in Alternator

The driving power from the prime-mover driving the alternator is lost but the alternator remains connected to the supply network; the field supply also remains on. The alternator will: A) get burnt B) behave as an induction motor but will rotate in the opposite direction C) behave as a synchronous motor and will rotate in the same direction D) behave as a synchronous motor but will rotate in a reverse direction to that corresponding to generator action

In an alternator if the winding is short pitched by 60 electrical degrees, its pitch factor will be: A) 1.0 B) 0.866 C) 0.75 D) 0.50

An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: A) 1000 rpm B) 920 rpm C) 950 rpm D) 970 rpm

The economic size of a conductor in transmission and distribution lines of electric power is decided by (a) Ohm’s law (b) Kelvin’s law (c) Kirchhoff’s law(d) Faraday’s law

Which alternator will have more number of poles ? (a) coupled to steam turbine (b) coupled to gas turbine (c) coupled to hydraulic turbine (d) None of the above

If the excitation of an alternator operating in parallel with other alternators decreased, its: (1) Power factor becomes more leading (2) Output Kw will change (3) Power factor becomes more lagging (4) Power factor becomes unity

Drop in alternator frequency is corrected by: (1) Damper winding (2) Increased prime mover output (3) Automatic voltage regulator (4) None of these

Two 3-phase, Y-connected alternators are to be paralleled to a set of common busbars. The armature has a per phase synchronous reactance of 1.7 Ohm and negligible armature resistance. The line voltage of the first machine is adjusted to 3300 V and that of the second machine is adjusted to 3200 V. The machine voltages are in phase at the ... are paralleled. Under this condition, the synchronizing current per phase will be  (A) 16.98 A (B) 29.41 A (C) 33.96 A (D) 58.82 A

A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a terminal voltage of 2000 V on open circuit. The magnitude of the internal voltage drop within the machine at a load current of 200 A is  (A) 1 V (B) 10 V (C) 100 V (D) 1000 V

A 8 pole alternator rotates at 750 r.p.m. Its frequency is

A 60 Hz, 2 pole alternator should run at • a. 3000 r.p.m. c. 1500 r.p.m. • b. 3600 r.p.m. d. 1800 r.p.m.

Is the speed of alternator is directly proportional to frequency?

At which power factor alternator is said to be overexcited?

Salient pole rotor is use for which speed?

Which rotor is use for high speed in turbo alternators?

The power factor of an alternator depends on?

In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

The magnitude of various voltage drops that occur in an alternator depends on?

In alternator where the voltage drop occurs?

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