Related Questions

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
A remain same
B go down
C improve
D none of the above
Two shafts A and B are made of the same material. The diameter of shaft A is twice as that of shaft B. The power transmitted by the shaft A will be __________ of shaft B.
A Twice
B Four times
C Eight times
D Sixteen times
The natural frequency of free torsional vibrations of a shaft is equal to (where q = Torsional stiffness of the shaft and $$I$$ = Mass moment of inertia of the disc attached at the end of a shaft)
A $$2\pi \sqrt {\frac{{\text{q}}}{I}} $$
B $$2\pi \sqrt {{\text{q}}I} $$
C $$\frac{1}{{2\pi }}\sqrt {\frac{{\text{q}}}{I}} $$
D $$\frac{1}{{2\pi }}$$
The radius of a friction circle for a shaft rotating inside a bearing is (where r = Radius of shaft and $$\tan \varphi $$  = Coefficient of friction between the shaft and bearing)
A $${\text{r}}\sin \varphi $$
B $${\text{r}}\cos \varphi $$
C $${\text{r}}\tan \varphi $$
D $$\frac{{\text{r}}}{2}\cos \varphi $$
The product of the tangential force acting on the shaft and its distance from the axis of the shaft (i.e. radius of shaft) is known as
A Bending moment
B Twisting moment
C Torsional rigidity
D Flexural rigidity
A synchronous motor can be used as a synchronous capacitor when it is
A under-loaded
B over-loaded
C under-excited
D over-excited
A synchronous motor can develop synchronous torque
A when under loaded
B while over-excited
C only at synchronous speed
D below or above synchronous speed
While starting a synchronous motor by induction motor action, field winding is usually
A connected to D.C. supply
B short-circuited by low resistance
C kept open-circuited
D none of the above
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
A power factor as well as armature current will decrease
B power factor as well as armature current will increase
C power factor will increase but armature current will decrease
D power factor will decrease and armature current will increase
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
A synchronous motor has no slip
B stator supply is not required to produce magnetic field
C mechanical load on the rotor remains constant
D synchronous motor has large airgap

Next steps