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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 are the advantages of salient pole alternator?
reduced noise. reduced windage loss. adoptability to low and medium speed operation.
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.
Which is true about salient pole rotor in synchronous generator?
Salient Pole Rotor Since the rotor is subjected to changing magnetic fields, it is made of steel laminations to reduce eddy current losses. Poles of identical dimensions are assembled by stacking laminations to the required length. A salient pole synchronous machine has a non-uniform air gap.
What are the main differences between cylindrical rotor and salient pole rotor synchronous generators?
In general, the Cylindrical Rotor type machines are confined to 2 and 4 pole turbine generators, while salient pole types are built with 4 poles upwards and include most classes of duty. Both classes of machine are similar in Stator construction point of view.
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.
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 is mean by salient pole?
: a magnet pole that projects toward the armature of an electric machine — compare consequent pole.
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 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 are the main parts of synchronous motor?
The Construction of Synchronous Motors 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 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.
Why are round rotor synchronous machines used at high speeds?
Since the rotor can be balanced easily and centrifugal forces will be evenly distributed, the rotor of the round (cylindrical) rotor generator can be run at higher rotational speed.
Why synchronous motors are not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
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.
Is kVA bigger than kW?
What is the difference between kW and kVa? kW is the unit of real power and kVA is a unit of apparent power (or real power plus re-active power). The power factor, unless it is defined and known, is therefore an approximate value (typically 0.8), and the kVA value will always be higher than the value for kW.
How do I convert kVA to kW?
Apparent power (kVA) x power factor (pf) = actual power (kW) e.g. 100 kVA x 0.8 = 80 kW. The formula for converting kW into kVA is: Actual power (kW) / power factor (pf) = apparent power (kVA)Jun 15, 2017.
Why motors are rated in kW?
Motor is rated in kW since it specifies the capacity of the motor to drive its load. It is the active power (kW) that is of interest when a motor drives a load. The motor converts the active power that it draws from the mains into mechanical power that the load consumes/demands. Thus, a motor is rated in terms of kW.
Which kind of motor is most suitable for turbo alternator which are designed to run at high speed?
Non-salient pole type or cylindrical type rotors are used in high-speed alternators or turbo-alternators having speed between 1500 rpm to 3000 rpm.
Why are turbo-alternators run at very high speeds?
The normal speed of a turbo generator is 1500 or 3000 rpm with four or two poles at 50 Hz (1800 or 3600 rpm with four or two poles at 60 Hz). The rotating parts of a turbo generator are subjected to high mechanical stresses because of the high operation speed.
Which type of rotor is suitable for low speed alternators?
The salient pole type of rotor is generally used for slow speed machines having large diameters and relatively small axial lengths. The poles, in this case, are made of thick laminated steel sections riveted together and attached to a rotor with the help of joint.
