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Objective:
To determine the direct & quadrature axis reactances of a salientpolealternator.
Apparatus:
1. Two A.C voltmeters
2. One A.C ammeter
3. Rheostats
4. A single throw triple pole switch
Theory:
The unsaturated values of Xd and Xq for a 3-phase synchronous machine may be
found by applying low values of balanced voltage to its armature, and driving its
rotor mechanically at a speed differing slightly from the normal synchronous speed,
the field circuit being open. The rotating armature m.m.f axis gradually changes, on
account of the 'slip ' between coincidenc4 with the polar & interpolar axes
successively. The reluctance of the magnetic circuit varies cyclically between an
upper & a lower limit, and the armature current consequently changes in the reverse
sense. The ratios of applied voltage to armature current gives the synchronous
reactances, using minimum ratio for Xq and maximum for Xd. Xd has the same
value as would be obtained from the normal no load and short circuit tests.
Procedure:
1. A coupled D.C motor very near to synchronous speed runs the salient- pole
synchronous machine. If the synchronous speed is 1500 rpm, the set is run at
1750 rpm.
2. The stator of the salient pole alternator is supplied from a low voltage (10-20
Volts), 3 -phase supply. The supply frequency is more than 50 Hz as the
supplying alternator is run at 1750 rpm.
3. The field is kept open and the maximum and minimum deflections in the
ammeter (to read the supply voltage) are read.
4. Xd, Xq are calculated.
Results:
Xd = Maximum V/Minimum I
Xq = Minimum V/ Maximum I
Discussion:
1. The alternator should not be run at exactly the synchronous speed, for then
instruments will give steady deflections. The stator voltage must be capable of
close adjustment. The slip must be very small. Otherwise the measurements will
be in error on account of eddy currents in the pole faces or the damper windings.
Page 2
If in the experiment, the slip is very large, and cannot be adjusted to a smaller
value, he measurements are liable to error.
2. The slip tends to pulsate because of fluctuation of torque with the relative pole
positions with the result that there is a tendency for Xd to be underestimated
Wiki User
∙ 13y ago
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How many poles as salient pole rotor?
'Salient' means 'sticking out', so if the pole sticks up from the rotor shaft, then it is a salient pole machine.
What is the priniciple of salient pole alternator?
The term, 'salient', simply means to 'stick out'. So a salient pole machine has field poles that stick out from the rotor. The principle of operation is the same as for any other generator.
What is salient and non salient pole alternator?
In salient pole alternator Xar is unequal in D-axis and Q-axis, due to non uniform air gap where as in non-salient pole Xar is equal in every axis due to uniform airgap between stator and rotor. Xar is armature reaction reactance.
What is the salient pole type field structure andnon silent pole type field structure in an alternator?
There are two types of rotors - salient pole and round rotor. Salient pole rotors have protuding poles that the coils are wrapped around, and are typically used when many poles are needed. The main electomagnetic difference is a salient pole machine naturally has a varying air gap between the rotor and the stator, due to the pole saliency.
What are the Types of alternators based on rotor construction?
Types of rotor-Salient pole or projected typeNon salient pole or cylindrical typeSalient type is used for low speed or medium speed motor where non salient type is used for high speed rotor.
COMPARE SALIENT POLE AND HNDRICAL ROTOR MACHINES?
sailant
What is meant by salient and non-salient pole machine?
for salient type motor Lq>Ld, and non-salient type motor Lq=Ld; Lq and Ld are q-d axis inductanceAnswer'Salient' means to 'stick out', so a 'salient pole' machine is one whose rotor windings are fitted to pole pieces that stick out from the rotor shaft. A 'non-salient pole' machine is one in which the windings are placed in slots machined along the length of the rotor.Salient pole machines run slower and have more poles than slotted-rotor machines, and are typically used in alternators run by water turbines; slotted-rotor machines are typically used in alternators run by high-speed steam/gas turbines.
What is the difference between salient pole and non salient pole machines?
Rotors used in Synchronous alternators can be classified into 1)Salient and 2)Non-Salient Pole Rotors. Salient pole rotors are used in application with speeds from 100 to 1500rpm. They are alternative known as "projected pole" type of rotors. The poles mounted on the rotor are made of laminations made of steel. The poles are connected to the rotor shaft by means of dovetail joints. Each pole has a pole shoe around which the winding is wound. The salient pole rotor is generally used in applications where the prime mover is a hydel turbine or a combustion engine which have low or medium speeds. Salient pole rotors usually contain damper windings to prevent rotor oscillations during operation. Non-salient pole rotors are generally used in application which operate at higher speeds, 1500rpm and above. The prime movers in these applications are generally gas or steam turbines. These are sometimes known as "drum rotors". The rotor is a cylinder made of solid forged steel. The slots on which the windings are fixed are milled on the rotor. The number of poles is usually 2 or 4 in number. Since these rotors are cylindrical, the windage loss is reduced. The noise produced is also less. These rotors have higher axial length. These rotors do not need damper windings.
How induction motor is made self starting?
just put a auxilari winding on the rotor (in the salient pole)..
How many different types of alternator are there for a 1998 fore contour?
type 1: single phase tree phase poly phase type 2: rotating armature rotating field type 3: salient pole machine non salient pole machine type 1: single phase tree phase poly phase type 2: rotating armature rotating field type 3: salient pole machine non salient pole machine
Why the synchronous motor is always a salient pole machine ie why don't we use a cylindrical pole machine as a synchronous motor?
The speed of the machine is tied to the power supply frequency and the number of poles the machine has. It becomes impractical to make a round rotor machine with many poles, so machines that spin at low revolutions will typically be salient designs. A two or four pole machine could be round rotor designs.
What is cylindrical rotor machine?
ok actually i am looking for the answer also but this is what i have got so far,you can understand cylindrical rotor in comparison to Salient pole machines. In cylindrical rotor, as it rotates, the air gap between the rotor and stator doesnt change due to its cylindrical shape, but for salient pole machine, due to its shap, the air gap changes as it rotates, due to those dents(laminations) and since air gap is fixed for cylindrical rotor,the magnetic path reluctance is independent in respect to its position to magnetic poles
