What is synchronous speed

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2 Answers

Answer :

Syn. Speed = (120 × supplying frequency) ÷ No. Of poles
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Answer :

this term sychronous speed related to AC  machines..

The speed depends on the EMF frequency and number of poles...
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Related questions

What will happen if the induction motor runs at synchronous speed ?

Description : What will happen if the induction motor runs at synchronous speed ?

Last Answer : Since there is always slip present in rotor it cannot run at synchronous speed no current will be developed hence no torque will developed

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Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

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What is the formula for synchronous speed ?

Description : What is the formula for synchronous speed ?

Last Answer : Synchronous speed formula Ns = 120f / p

A four-pole 60-hertz induction motor has a synchronous speed of 1800 RPM and a slip of 4 percent at full load. What will be its full load speed? A. 1728.0 RPM B. 1730.7 RPM C. 1800.0 RPM D. 1872.0 RPM

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If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase

Description : If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase

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The synchronous speed of an induction motor is the ________. A. speed at which the rotor turns B. speed of the rotating field C. frequency of the rotor current D. slip in per cent of rotor RPM

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An increase in which of the listed conditions will increase the speed of a synchronous motor? A. Frequency B. Voltage C. Armature current D. Inductance

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The difference between the synchronous speed of an induction machine and its operating speed (slip) may be correctly expressed _____________. A. as a percent of synchronous speed B. as a decimal fraction of synchronous speed C. directly in revolutions per minute D. as all of the above

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In an AC synchronous motor electric propulsion plant, propeller speed is controlled by varying the _____________. A. prime mover speed B. electric coupling field strength C. number of energized main motor poles D. propulsion generator field strength

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Description : Why the induction motor never runs at synchronous speed?

Last Answer : If rotor & stator have same speed, no relative motion {Nr = Ns (1-s)}. Slip is zero, no voltage induce in rotor Current is zero, then torque is zero (T ∞ E2 I2 cos φ2). Thus induction motor never runs at synchronous speed.

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Description : Why a 3-phase synchronous machine will always run at synchronous speed?

Last Answer : Because of the magnetic coupling between the stator poles and rotor poles the motor runs exactly at synchronous speed.

What would happen if synchronous speed is equal to rotor speed?

Description : What would happen if synchronous speed is equal to rotor speed?

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What is Synchronous speed?

Description : What is Synchronous speed?

Last Answer : The speed at which rotating magnetic field of three Phase Induction motor rotates is called synchronous speed. Ns=120f/p

Why a synchronous motor is a constant speed motor?

Description : Why a synchronous motor is a constant speed motor?

Last Answer : When load increase in synchronous motor the load angle δ also increases but speed remains constant. The further increase in load cause further increase in load angle. When load angle reaches ... out of synchronism. Hence the motor rotates at synchronous speed otherwise it comes out of synchronism.

What is the effect on speed if the load is increased on a 3 phase synchronous motor?

Description : What is the effect on speed if the load is increased on a 3 phase synchronous motor?

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Description : A single phase Hysteresis motor (A) can run at synchronous speed only (B) can run at sub synchronous speed only (C) can run at synchronous and super synchronous speed (D) can run at synchronous and sub synchronous speed

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If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.

Description : If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.

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The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be _________. (A) 1690 rpm (B) 1750 rpm (C) 1500 rpm (D) 1710 rpm

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Last Answer : (D) 1710 rpm

The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. (A) universal (B) synchronous (C) DC shunt (D) two-phase

Description : The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. (A) universal (B) synchronous (C) DC shunt (D) two-phase

Last Answer : Ans: A Universal motor has same characteristics as DC series motor and also known as an a.c series motor.

In a 3-phase synchronous motor (A) the speed of stator MMF is always more than that of rotor MMF. (B) the speed of stator MMF is always less than that of rotor MMF. (C) the speed of stator MMF is synchronous speed while that of rotor MMF is zero. (D) rotor and stator MMF are stationary with respect to each other.

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Last Answer : Ans: D Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore, rotor & stator mmf are stationary w.r.t each other.

The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine.

Description : The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine.

Last Answer : Ans: all options are correct

When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque.

Description : When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque.

Last Answer : (D) no torque.

A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed.

Description : A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at ... more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed.

Last Answer : (B) continue to run at synchronous speed.

Derive the relationship between Synchronous speed (Ns) and frequency (f) of alternator.

Description : Derive the relationship between Synchronous speed (Ns) and frequency (f) of alternator.

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A hydraulic turbine having rated speed of 250 rpm is connected to a synchronous generator. In order to

Description : A hydraulic turbine having rated speed of 250 rpm is connected to a synchronous generator. In order to produce power at 50 Hz, the number of poles required in the generator are (A) 6 (B) 12 (C) 16 (D) 24

Last Answer : A hydraulic turbine having rated speed of 250 rpm is connected to a synchronous generator. In order to produce power at 50 Hz, the number of poles required in the generator are 24

The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction

Description : The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction machine is  (A) 107.14 rpm in forward direction (B) 107.14 rpm in reverse direction (C) 5250 rpm in forward direction (D) 5250 rpm in reverse direction

Last Answer : The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction machine is 107.14 rpm in forward direction 

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

Description : If an induction machine is run at above synchronous speed, it acts as

Last Answer : If an induction machine is run at above synchronous speed, it acts as an induction generator.

In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will?

Last Answer : In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.

Centrifugal switch disconnects the auxiliary winding of the motor at about what percent of synchronous speed?

Last Answer : Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.

If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in?

Last Answer : If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.

The operating speed of a synchronous motor can be changed to new fixed value by?

Last Answer : The operating speed of a synchronous motor can be changed to new fixed value by changing frequency.

If we change the excitation of synchronous machine will it affect on motor speed?

Description : If we change the excitation of synchronous machine will it affect on motor speed?

Last Answer : No, If we change the excitation of synchronous machine it will not affect on motor speed.

Synchronous motor always runs at which speed?

Description : Synchronous motor always runs at which speed?

Last Answer : Synchronous motor always runs at synchronous speed.

Compare characteristics of asynchronous and synchronous transmission mode.

Description : Compare characteristics of asynchronous and synchronous transmission mode (four points). 

Last Answer : Synchronous transmission Asynchronous transmission 1. Synchronous transmission are synchronized by an external clock. 1. Asynchronous transmission are synchronized by special signals along the transmission ... for transferring a small amount of data as it is simple and economical.

Compare synchronous and asynchronous counter.

Description : Compare synchronous and asynchronous counter.

Last Answer : Asynchronous Counter Synchronous Counter In an Asynchronous Counter the output of one Flip Flop acts as the clock Input of the next Flip Flop. In a Synchronous Counter all the Flip Flop's are ... Also called as serial counter Also called as Parallel Counter

The synchronous motor can be used as a capacitor

Description : The synchronous motor can be used as a capacitor • By increasing excitation • By decreasing excitation • By increasing speed • By decreasing speed

Last Answer : The synchronous motor can be used as a capacitor By increasing excitation

A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously

Description : A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased  1. The power factor decreases upto a certain value of field current and thereafter it increases.  2. The armature current ... the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

Last Answer : A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased  1. The power factor decreases upto a certain value of field current and thereafter it increases.  2. The armature current ... the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

The swing equation for a synchronous machine is based on

Description : The swing equation for a synchronous machine is based on (A) relative motion between load angle and stator magnetic field (B) maximum power flow possible through a particular point (C) net torque and angular displacement (D) relation between excitation voltage and excitation current

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A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of...

Description : A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 kV is (A) 2/15 p.u. (B) 5/6 p.u. (C) 1.0 p.u. (D) 1.2 p.u.

Last Answer : A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 kV is 5/6 p.u.