Why do turbo alternators use non salient pole?

The rotor of a turbo generator is a non-salient pole type usually with two poles. Salient rotors will be very noisy and with a lot of windage loss. The rotating parts of a turbo generator are subjected to high mechanical stresses because of the high operation speed.

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Correspondingly, what is the difference between salient pole and non salient pole?

Salient pole rotors have large diameter and shorter axial length. They are generally used in lower speed electrical machines, say 100 RPM to 1500 RPM. Flux distribution is relatively poor than non-salient pole rotor, hence the generated emf waveform is not as good as cylindrical rotor.

Similarly, why is the rotor of a turbo alternator made cylindrical? Rotor of Turbo alternator Smooth cylindrical(non-salient pole) type rotor is used in the turbo alternator. Owing to the high-speed, they have either two poles or four poles. In order to prevent the peripheral speed from exceeding the safe limit, the diameter of the rotor is kept down.

Similarly, what does salient pole mean?

Definition of salient pole. : a magnet pole that projects toward the armature of an electric machine — compare consequent pole.

What is meant by turbo alternator?

Turbo-alternators are basically hydrogen cooled cylindrical rotor alternators used to generate electric power in generating stations. They have only 2 poles and are run by a 3000 rpm turbine for 50 Hz machine and 3600 rpm for 60 Hz machine.

Related Question Answers

How many types of rotors are there?

Read More. For induction motors, there are two types of rotors: (1) squirrel cage and (2) wound rotor. Of these two types there are many variations.

What does non salient mean?

1 prominent, conspicuous, or striking. a salient feature. 2 (esp. in fortifications) projecting outwards at an angle of less than 180°

What is difference between salient pole and cylindrical rotor?

Salient pole rotors have large diameter and shorter axial length. They are generally used in lower speed electrical machines, say 100 RPM to 1500 RPM. Flux distribution is relatively poor than non-salient pole rotor, hence the generated emf waveform is not as good as cylindrical rotor.

What is meant by salient pole alternator?

Salient Pole Synchronous Alternator: Salient Poles are laminated in order to reduce eddy currents. They are used in hydraulic turbines or diesel engines. Salient pole generators will have typical speed about 100 to 375 rpm.

What is synchronous speed?

In a motor, synchronous speed is the speed at which the magnetic field rotates. Depending on motor design, the actual mechanical speed may be equivalent (synchronous motor) or slightly smaller (asynchronous motor). The synchronous speed is a function of:The electrical frequency used, typically 60 Hz or 50 Hz.

What is reluctance power?

Reluctance power is the additional power developed in synchronous motor or synchronous generator due to saliency of the rotor. The amount of this power may not be great but its main advantage lies in increasing the synchronising power and thereby improving the stability of the machine.

How does a rotor work?

The rotor is a moving component of an electromagnetic system in the electric motor, electric generator, or alternator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor's axis.

What is meant by two reaction theory?

Two Reaction Theory was proposed by Andre Blondel. The theory proposes to resolve the given armature MMFs into two mutually perpendicular components, with one located along the axis of the rotor of the salient pole. It is known as the direct axis or d axis component.

What is meant by induction motor?

Definition of induction motor. : an alternating-current motor in which torque is produced by the reaction between a varying magnetic field generated in the stator and the current induced in the coils of the rotor.

What is the slip?

Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol 'S'.

What is damper winding?

Definition of damper winding. : a short-circuited squirrel-cage winding placed in the pole faces and around the pole shoes of synchronous machines, the currents induced in the winding by the periodic variations in synchronous speed having the effect of a damper. — called also amortisseur.

What are the different types of rotor of alternator?

There are mainly two types of rotors used in construction of alternator: Salient pole type. Cylindrical rotor type.

Salient Pole Type

• They have a large horizontal diameter compared to a shorter axial length.
• The pole shoes covers only about ²/₃rd of pole pitch.
• Poles are laminated to reduce eddy current loss.

Why synchronous motors are not self starting?

Key Point : As a result, the average torque exerted on the rotor is zero. And hence the synchronous motor is not self starting. This is because the speed with which rotating magnetic field is rotating is so high that it is unable to rotate the rotor from its initial position, due to the inertia of the rotor.

What is synchronous reactance?

The Synchronous Reactance (X_S) is the imaginary reactance employed to account for the voltage effects in the armature circuit produced by the actual armature leakage reactance and by the change in the air gap flux caused by the armature reaction.

What is saliency in synchronous machines?

(1) Salient pole machines develop some extra power due to saliency. This is called reluctance power. Thus, due to saliency, a synchronous motor can run at light load even without field energized, like a reluctance motor.

Which rotor is used in synchronous motor?

Cylindrical, round rotors, (also known as non salient pole rotor) are used for up to six poles. In some machines or when a large number of poles are needed, a salient pole rotor is used. The construction of synchronous motor is similar to that of a synchronous alternator.

Why is damper winding used in salient pole synchronous machine?

The primary function of damper winding in a synchronous machine is to prevent the phenomenon called hunting. If load on a synchronous machine is changed suddenly, its power angle has to change accordingly. However, change in power angle doesn't occurr smoothly. The rotor starts swinging around the new power angle.

How many Poles does an alternator have?

For a slower diesel engine a 4-pole alternator is typical. This runs at 1500 or 1800 rpm for 50 or 60Hz. This is also a cylindrical design. For water turbines a 6 to 12 pole alternator may be used.

Is an alternator 3 phase?

Three-phase alternators have three sets of windings; they're more efficient than a single-phase alternator, which produce a single-phase AC current. When working properly, the three windings produce three currents that make up the three phases. Adding all three together produces the total AC output of the stator.