Electrical Machines Objective Questions – Set 12

A DC Shunt Motor having shunt field resistance of 250 Ω and armature resistance of 0.5 Ω is connected to 250 V supply and load current of 21 A. What is the back emf generated ?

A DC compound motor has

The armature of a DC motor is laminated to reduce

A DC motor with armature resistance of 0.5 ohms connected directly to a 220 Volt supply. If the armature is stationary then the current flowing through the armature is

Which type of motors are preferred in lifts?

If the full load speed of 3-phase, 50Hz induction motor is 950 rpm, what is its half load speed nearly equals to?

Which of these types of motor is used in elevators?

If an induction machine is run at above the synchronous speed it acts as

In the 3-phase induction motor, the resultant flux is of a constant nature and is

Which type motors are preferred for lathes?

What is the emf generated by a 4 pole Lap connected DC Motor rotating at 1500 rpm having 1000 conductors and useful flux per pole is 0.4 mWb.

Which type of DC Motor is preferred for Paper mills?

Swinburnes test is applicable to

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

In electric locomotive which of the following motor are used ?

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

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

Which type of motors uses slip rings?

On what factors the speed of dc motor depends?

In a 3-phase induction motor, torque and supply voltage are related as

Find the developed torque DC Series Motor having armature resistance of 0.2 Ω and taking armature current of 60 A is connected to 250 V supply. Considered brush drop of 1 V each.

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

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

In a DC Shunt Motor if the load current increases then field flux

The armature resistance of a permanent magnet dc motor is 0.8 W. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be

The rotor slots are slightly skewed in squirrel cage induction motor to

Which of the following motor is expensive for same Kw output rates?

Semi closed slots or totally closed slots are used in induction motors, essentially to

The power factor of an induction motor operating at no load will have a value around

The speed of a 3-phase induction motor operating in its stable region