Question is ⇒ A synchronous motor running with normal excitation adjusts to load increases essentially by increase in, Options are ⇒ (A) back e.m.f., (B) armature current, (C) power factor, (D) torque angle, (E) , Leave your comments or Download question paper.

Question is ⇒ A synchronous motor running with normal excitation adjusts to load increases essentially by increase in, Options are ⇒ (A) back e.m.f., (B) armature current, (C) power factor, (D) torque angle, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
A.	back e.m.f. [Wrong Answer]
B.	armature current [Correct Answer]
C.	power factor [Wrong Answer]
D.	torque angle [Wrong Answer]
View Answer 8 -4 Explanation:- Answer : B Discuss it below : LiFE CHAnGer Said on 2020-04-23 19:22:33 Jbg Q.194 !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ Slip-rings in a synchronous motor carry
direct current
alternating current
no current
all of the above

⇒ A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
speed of the motor is reduced
power factor is decreased
Eb (back e.m.f.) becomes less than V (applied voltage)
Er (net resultant voltage) in armature is increased

⇒ To limit the operating temperature an electrical machine should have proper
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⇒ A three-phase synchronous motor will have
no slip-rings
one slip-ring
two slip-rings
three slip-rings

⇒ The armature current of the synchronous motor
has large values for low excitation only
has large values for high excitation only
has large values for low and high excitation
any of the above

⇒ A synchronous motor can operate at
lagging power factor only
leading power factor only
unity power factor only
lagging, leading and unity power factors

⇒ In a synchronous machine in case the axis of field flux is in line with the armature flux, then
the machine is working as synchronous generator
the machine is working as synchronous motor
the machine will vibrate violently
none of the above

⇒ If one-phase of a 3-phase synchronous motor is short-circuited, motor
will refuse to start
will overheat in spots
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⇒ In a synchronous motor, V-curves represent relation between
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field current and power factor

⇒ The net armature voltage of a synchronous motor is equal to the
vector sum of Eb and V
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arithmetic difference of Eb and V
vector difference of Eb and V

⇒ In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be
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⇒ As the load is applied to a synchronous motor, the motor takes more armature current because
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the rotor by shifting its phase backward causes motor to take more current
the back e.m.f. decreases causing ah increase in motor current
the rotor strengthens the rotating field casuing more motor current

⇒ When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
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decreases to half the original value
tends to becomes zero
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⇒ Synchronous motors are
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⇒ The magnitude of field flux in a 3-phase synchronous motor
remains constant at all loads
varies with speed
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⇒ The power factor of a synchronous motor is better than that of induction motor because
stator supply is relieved of responsibility of producing magnetic field
mechanical load on the motor can be adjusted
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synchronous motor has large air gap

⇒ Synchronsizing power of a synchronous machine is
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inversely proportional to the synchronous reactance
equal to the synchronous reactance
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⇒ The speed regulation of a synchronous motor is always
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⇒ If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
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the motor stops
it continues to run at the same speed
it runs at a very high speed

⇒ Stability of a synchronous machine
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remains unaffected with increase in excitation
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⇒ In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
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⇒ In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
the motor is said to be fully loaded
the torque generated is maximum
the excitation is said to be zero per cent
the excitation is said to be hundred per cent

⇒ A synchronous motor develops maximum power when load angle is
45°
60°
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⇒ 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
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⇒ In a synchronous motor, the maximum power developed depends on all of the following except
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maximum value of coupling angle
direction of rotation
supply voltage

Jbg Q.194