Electrical Machines Objective Questions – Set 9

What is the highest possible speed by turbo alternators?

Which type of motors are preferred in lifts?

Which of the following DC Motor is used in paper machines ?

In a 3-phase induction motor, if the supply voltage and frequency are reduced by the same ratio, then slip at which maximum torque occurs is

What is the reason for stationary armature essential in alternators above 5 KVA?

Two identical loss less series motors connected in series across a dc supply voltage, runs at speed of N₁ and N₂, then ratio of their output power is

On which of the following factor/factors the speed of a DC motor depends upon?

The speed of a motor falls from 1100 r.p.m at no-load to 1050 r.p.m at rated load. The speed regulation of motor is

A dc motor with armature resistance of 0.5 ohms connected directly to a 230 Volt supply. If the armature is stationary then the current flowing through armature is

For the speed control of polyphase squirrel cage induction motor, if frequency of operation is decreased with

A DC compound motor has

In DC series motor the speed is ______________ proportional to the armature current.

Which of these types of motor is used in elevators?

In a DC Shunt Motor if the load current increases keeping the terminal voltage constant, then flux will

A 250 volt dc series motor having an armature resistance of 0.2 Ω takes an load current of 60 A. What will be the torque produced at the shaft of the motor? Consider brush drop of 1V.

Which of the following motor is more expensive for same KW output rating ?

For a standard frequency the machine operates at a particular speed known as

For a DC Shunt Motor having armature resistance of 0.5 Ω and 2A armature current at no-load, when the armature current is changed to 20A at loaded condition the speed is 1000 r.p.m. What is the speed at no-load?

Rotor resistance speed control is used in

The dc motor which can provide zero speed regulation at full load without any controller, is

Which of the following alternators contain large number of poles?

Swinburne's test is applicable to

Which of the following rotor requires damper winding?

For 250 volt DC Shunt Motor the armature and field resistance are 0.5 ohm and 250 ohm respectively. What will be the back e.m.f. produced when it takes a load current of 21A.

The armature of a DC motor is laminated to reduce

Which type of motors are used for lathes?

What will be the e.m.f. generated by a 4 pole lap connected DC Generator rotating at 1500 r.p.m.? Its flux per pole is 0.4 mWb and total no of armature conductors is 1000.

For satisfactory performance of 3-phase 480V, 60 Hz induction motor, the supply voltage at 50 Hz should be equal to

In electric locomotives which of the following motor are used ?

Which of the following is the largest conversion device?