APPSC Inspector of Factories Electrical Solved Papers

The armature time constant $T_a$ is applicable to:

The various components of armature short circuit current of a 3 phase alternator without amortisseur windings:

(i) Subtransient component
(ii) Transient component
(iii) Second harmonic component
(iv) DC component
(v) Fundamental Frequency Component

From the above, the correct answer is:

A synchronous generator has higher power handling capability when operating at:

In synchronous machine connected to an infinite bus, if rotor speed departs from synchronous speed then:

In a synchronous machine connected to an infinite bus, if rotor speed departs from synchronous speed, then the rotor oscillations can be investigated by including the:

(i) damping power
(ii) synchronous power
(iii) inertia power
(iv) shaft power

From above, the correct answer is:

An alternator of frequency 50.2 Hz is to be synchronized with an infinite bus of frequency 50 Hz by means of three dark lamp method. The lamp flicker per minute will be:

An alternator with frequency $f_1$ is to be synchronized with an infinite bus of frequency $f$. For proper synchronization:

A 3-phase alternator with line voltage $V_1$ is to be synchronized with infinite bus. The maximum value of r.m.s voltage across synchronizing switch would be:

One alternator, with subtransient reactance of 0.25 p.u. is to be synchronized with infinite bus by three dark lamp method. If the synchronizing switch is closed when the lamps are the brightest, then the synchronizing current would be:

The division of active power amongst alternators running in parallel depends upon:

The division of reactive power amongst alternators running in parallel depends upon :
(i) Speed load characteristics of prime movers
(ii) Volt-Ampere characteristics of alternators
(iii) Excitation voltages of alternators
From these, the correct answer is:

An alternator is synchronized with infinite bus. Now if its field current is decreased, then its armature current:

With a single alternator connected to infinite busbar supplies a local load, the change in excitation of the machine results in change of:

A 3-phase synchronous machine is synchronized with infinite bus. Now the prime mover is disconnected from the synchronous machine. With this, the synchronous machine would :

A 3 phase synchronous machine is synchronized with an infinite bus. Now steam input to synchronous machine is increased. With this, synchronous machine starts working as:

A 3 phase alternator is supplying power to infinite generator at a lagging pf with constant steam input, alternator excitation is increased. With this:

A synchronous machine has excitation voltage of $0.8\angle15^{\circ}$ and the infinite bus voltage of $1.0\angle0^{\circ}$. The synchronous machine is working as:

In parallel operation of alternators, the synchronizing power is maximum if armatures have:

If two alternators A and B of same rating and power factors 0.6 lagging and 0.4 leading respectively are connected in parallel, the overall p.f. is:

Two alternators A and B, running in parallel, supplies power to a resistive load. For the same terminal voltage and steam inputs, if excitation of alternator A is increased, then:

Two alternators A and B, running in parallel, supply power P to a resistive load. Then the two alternators share equal powers. For the same load power P, the driving torque of alternator A is increased while that of B is suitably adjusted. With this:

The maximum torque that a synchronous motor can deliver is proportional to:

When zero-sequence currents are flowing in the armature winding of a synchronous machine, the nature of air gap field is:

When negative sequence currents are flowing in the armature winding of a synchronous machine, the nature of air gap field is:

In a three phase induction motor coupled with constant torque load, if supply voltage is kept constant but supply frequency is reduced below the rated value, then: