What is the effect of field failure of salient pole synchronous motor connected with infinite bus?

16. What is the effect of the field failure of salient pole synchronous motor connected with infinite bus? (a) Reduce motor torque and speed.

What happens to the synchronous motor when the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?

When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor run as a variable reluctance motor. Reluctance torque is the torque generated because the motor is moving to a position where the reluctance seen by the armature flux is declining.

How does synchronous motor behaves at no load?

A synchronous motor running with no load will lead the current i.e. leading power factor like a capacitor. The synchronous condenser is used in power lines to improve power factor, power factor correction by connecting it along with transmission lines.

What happened to synchronous motor if only field is excited?

As the Field Winding is excited by AC source, an alternating / pulsating magnetic flux will be produced. The armature conductor at Stator will not see any change in flux due to backward rotating field flux and hence no EMF will be generated in the Armature Terminal of Alternator.

When a synchronous motor is connected to an infinite bus while operating on leading power factor?

When the synchronous motor connected to infinite bus bars has at constant full load, 100\% excitation, and unity power factor (p.f.), then on changing the excitation only, the armature current will have leading p.f. with over-excitation.

When an alternator is connected to infinite bus bar?

The frequency and terminal voltage of an alternator remains same as it is connected to infinite bus bar. If driving torque is decreased, the power angle δ must decrease correspondingly. If it becomes zero, no power is transferred to the infinite bus. The prime mover will only supply the losses.

What happens when rotor excitation fails in a salient pole type synchronous motor?

The field created by the rotor windings gets locked with this rotating magnetic field of the stator and also rotates at the same speed. If the excitation of the generator fails, suddenly there will be no more magnetically locking between the rotor and rotating magnetic field of the stator.

Why synchronous motor produces torque at synchronous speed?

In the synchronous AC motor, the speed of rotation is synchronized to the frequency of the AC input current. The torque of a synchronous motor is produced by the phase difference between the rotating magnetic field and the rotor.

Why are synchronous motors not started under load?

3.2. Synchronous motors are inherently not able to self-start on an AC power source with the utility frequency of 50 or 60 Hz. As stated in Chapter 1, this is because synchronous motors can develop a torque only when running at the synchronous speed.

When a synchronous motor operating on leading power factor while it is connected to an infinite bus?

When motor is over excited that means?

Synchronous motor: Leading power factor: If field excitation is such that Eb > V the motor is said to be over-excited and it draws leading current. So that the power factor improves. Unity power factor: If field excitation is such that Eb = V the motor is said to be normally excited.

What is the developed reluctance torque of salient pole synchronous motor?

In a salient pole synchronous motor, the developed reluctance torque attains the maximum value when the load angle in electrical degrees is A three-phase, 50 Hz, star-connected cylindrical-rotor synchronous machine is running as a motor.

Why does a synchronous motor run as an induction motor?

If damper windings are present or field circuit is short circuited, motor will run as an induction motor, at a speed slightly less than synchronous. But if they are not present, the motor will continue running at synchronous speed under no load due to the presence of reluctance torque.

What happens to the motor when the field supply is switched off?

In fact, the motor is now a synchronous reluctance motor. If the field supply is switched off, the motor will not rotate at synchronous speed, instead the rotor will slowly decelerate and comes to stand still position.

What is the reactance of a non-salient pole synchronous generator?

A non-salient pole synchronous generator having synchronous reactance of 0.8 pu is supplying 1 pu power to a unity power factor load at a terminal voltage of 1.1 pu. Neglecting the armature resistance, the angle of the voltage behind the synchronous reactance with respect to the angle of the terminal voltage in degrees is ________.