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Advantages of salient-pole type construction are : They allow better ventilation. The pole faces are so shaped that the radial air gap length increases from the pole center to the pole tips so that the flux distribution in the air-gap is sinusoidal in shape which will help the machine to generate sinusoidal emf.
What is salient pole synchronous machine?
Salient Pole Synchronous Alternator: They are used in hydraulic turbines or diesel engines. As the speed of the water turbine is slow hence more number of poles are required to attain the frequency. Therefore Salient pole machines will have typically number of poles will be between 4 to 60.
What are the advantages of salient pole alternator?
reduced noise. reduced windage loss. adoptability to low and medium speed operation.
Which is the value for salient pole synchronous generator?
The power developed in salient pole synchronous machine P = EV/Xd * sinδ + V²/2 * (Xd – Xq)/(Xd*Xq) *sin2δ Where E = Excitation value V = Terminal voltage Xd = Direct axis reactance, Xq = Quadrature axis reactance δ = load angle Power due to reluctance = V²/2 * (Xd – Xq)/(Xd*Xq) *sin2δ Therefore, in salient pole.
What are synchronous generators used for?
Synchronous generators are commonly used for variable speed wind-turbine applications, due to their low rotational synchronous speeds that produce the voltage at grid frequency. Synchronous generators can be an appropriate selection for variable speed operation of wind turbines [166,167].
What is mean by salient pole?
: a magnet pole that projects toward the armature of an electric machine — compare consequent pole.
What are the types of synchronous machine?
Synchronous motors can be classified into two types based on how the rotor is magnetized.This type of synchronous motor is divided into three categories and is available in three designs, each of which has unique features: Hysteresis Synchronous Motors. Reluctance Synchronous Motors. Permanent Magnet Synchronous Motors.
Why are alternators rated in KVA and not in kw?
If we connect inductive or capasitive load (When power factor is not at least unity), The output would differ than as there are losses occurs due to low power factor. For this reason, KVA is an apparent power which does not take in to account the PF (Power factor) instead of KW (Real Power). And kVA = KW / Cos θ.
What kind of rotor is most suitable for turbo alternator?
177. What kind of rotor is most suitable for turbo-alternators which are designed to run at high speed? 178. The power developed in the alternator having salient type rotor is less than of having non-salient pole.
How many types of rotor are used in alternator?
There are mainly two types of rotors used in construction of alternator: Salient pole type. Cylindrical rotor type.
What is the value of load angle?
Value of load angle & internal machine angle for maximum power developed in synchronous motor is 90° electrical, 90° electrical.
What is meant by synchronous machine?
: a dynamoelectric machine (such as a generator or motor) that has a constant magnetic field and an armature which receives or delivers alternating current in synchronism with the motion of the machine and at a frequency equal to the product of the number of pairs of poles and the speed of the machine in revolutions.
What do you understand by synchronous impedance?
The synchronous impedance is determined from the O.C.C and S.C.C. It is the ratio of the open-circuit voltage to the short circuit current. When the O.C.C and S.C.C are linear, the synchronous impedance ZS is constant. The flux under test conditions is the same as that under load conditions.
What are the two types of synchronous generators?
Types of synchronous machines Hydrogenerators : The generators which are driven by hydraulic turbines are called hydrogenerators. These are run at lower speeds less than 1000 rpm. Turbogenerators: These are the generators driven by steam turbines. Engine driven Generators: These are driven by IC engines.
Why do we need synchronous machine?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.
What is the principle of synchronous generator?
The principle of operation of synchronous generator is electromagnetic induction. If there exits a relative motion between the flux and conductors, then an emf is induced in the conductors.
What is meant by non salient pole?
Non-salient pole rotors are cylindrical in shape having parallel slots on it to place rotor windings. Damper windings are not needed in non-salient pole rotors. Flux distribution is sinusoidal and hence gives better emf waveform. Non-salient pole rotors are used in nuclear, gas and thermal power plants.
What are the main parts of a synchronous machine?
A synchronous motor is generally made up of two parts, a stator the stationary part of the machine that carries the armature winding in which the voltage is generated, and a rotor the rotating part of the machine that produces the main field flux.
What do you mean by synchronous speed?
: a definite speed for an alternating-current machine that is dependent on the frequency of the supply circuit because the rotating member passes one pair of poles for each alternation of the alternating current.
What is the slip?
Slip is the differentiation between synchronous and asynchronous speed. The difference between the synchronous speed of the electric motor magnetic field, and the shaft rotating speed is slip – measured in RPM or frequency. Slip increases with increasing load – providing a greater torque.
What is the main disadvantage of synchronous motors?
Disadvantages or Demerits: Synchronous motors requires dc excitation which must be supplied from external sources. Synchronous motors are inherently not self starting motors and needs some arrangement for its starting and synchronizing. The cost per kW output is generally higher than that of induction motors.
What is the difference between synchronous and asynchronous machine?
The synchronous motor is a type of AC motor that runs at synchronous speed. The asynchronous motor is a type of AC motor that runs on speed less than the synchronous speed. It operates on the principle of magnetic interlocking between rotor and stator field. it is always less than synchronous speed.
