In a loaded dc motor, if the brushes are given a shift from the inter-pole axis in the direction of rotation, then the commutation will
If two 8-pole dc machines of identical armature are wound, one with lap winding and the other with wave winding, then
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Consider the following statements regarding synchronous machines:
1. In an alternator, armature mmf leads the field flux
2. In an alternator, airgap flux lags the field flux
3. In a synchronous motor, armature mmf leads the field flux
4. In an alternator, field flux lags the armature current
From these, the correct answer is
The pitch factor, in rotating electrical machinery, is defined as the ratio of resultant emf of a
Consider the following statements:
The use of inter-poles in dc machines is to counteract the
1. Reactance voltage
2. Demagnetizing effect of armature mmf in the commutating zone
3. Cross-magnetizing effect of armature mmf in the commutating zone
Which of these statement(s) is/are correct?
Consider the following statements:
In the above figure, the curves pertain to the DC motor
A. Speed vs Armature current characteristic of a DC shunt motor
B. Torque vs Armature current characteristic of a DC shunt motor
C. Speed vs Armature current characteristic of a DC series motor
D. Torque vs Armature current characteristic of a DC series motor
Due to low supply voltage for a 40 HP, 3-phase induction motor, which of the following equipment can be used to boost the voltage?
The injected emf in the rotor of induction motor must have
In a split phase motor, the ratio of number of turns for starting winding to that for running winding is
A synchronous motor connected to infinite bus-bars has constant full-load, 100% excitation and unity p.f. On changing the excitation alone, the excitation current will have
If a 3-phase alternator is short-circuited at its terminal, then the initial value of short-circuit current will be limited by ________.
In the below given torque/speed characteristics of an induction motor, stable region is ________.
What is the use of the circuit shown in the figure below?
As compared to a split phase motor, a capacitor start motor has _____.
Why is the air gap between the yoke and armature of an electric motor kept smaller?
For a particular kW rating of an induction motor, the kVAR rating of the shunt capacitor required is _______.
The induction motors develop which of the following at low frequency of the order ½ Hz to 10 Hz?
The open slots are more commonly used in the stator of a synchronous machine because _______.
A. The inductance of the winding is less
B. They facilitate the insertion of form wound and insulated coils
Three singly-excited electromagnetic structures are shown in the figures labelled I, II and III (R-Rotor, S-Stator), the reluctance torque can be developed in _______.