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What are the advantages of skewed slots in the rotor of a squirrel cage rotor?
Wiki User
∙ 9y ago
It helps to put on a little more traction. The rotor will stay on better because it is not as slippery.
Wiki User
∙ 9y ago
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Why are the rotor bars of a squirrel cage induction motor usually slanted i.e. not entirely parallel with the shaft?
The squirrel cage is skewed so that the force applied to the rotor it continuous. If they were straight then the force would be jerky, as whole of the bar is cutting the magnetic field lines at the same time. With the bars skewed the amount of the bar cutting the field line grows continuously and the next bar starts cutting the field lines as the first finishes. also, slots are skewed to get uniform torque ,reduce the magnetic locking (also called COGGING EFFECT) between stator and rotor,and thirdly to reduce the magnetic humming noise during running condition
Why rotor slots is more than stator slots in induction motor?
rotor slot more. it is to get a large rotor inductance value of inductance the stator windings
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.
Why do you use slotted armatures in dc machines?
Those slots, or areas where metal was removed serve to balance the motor's armature. This is similar to the concept of "balancing" a wheel on a car.Metal material is 'shaved' or notched ( removed) from the side of the armature which is too heavy, ( and causes a ' wobble' as the RPM's are increased.)However, On a car, wheel weights are added to the OPPOSITE side of the wheel's heaviest spot of imbalance, until the wheel can be spun at a high speed, with no wobble.AnswerThe slots carry the armature conductors, while minimising the air gap between the rotor and and the stator (to minimise the reluctance of the magnetic circuit)!They have nothing to do with 'balancing' the armature.
How does generator works?
A simple AC generator consists of:Figure 3 Simple AC Generator(a) a strong magnetic field, (b)conductors that rotate through thatmagnetic field, and (c) a means bywhich a continuous connection isprovided to the conductors as theyare rotating . The strongmagnetic field is produced by acurrent flow through the field coilof the rotor. The field coil in therotor receives excitation throughthe use of slip rings and brushes.Two brushes are spring-held incontact with the slip rings toprovide the continuous connectionbetween the field coil and theexternal excitation circuit. The armature is contained within the windings of the stator and isconnected to the output. Each time the rotor makes one complete revolution, one complete cycleof AC is developed. A generator has many turns of wire wound into the slots of the rotor. The magnitude of AC voltage generated by an AC generator is dependent on the field strengthand speed of the rotor. Most generators are operated at a constant speed; therefore, the generatedvoltage depends on field excitation, or strength.
What is squirrel cage in motors?
When the number of rotor and stator poles are equal in the motor and if these rotor poles have opposite polarity with respect to the stator poles magnetic locking occurs. This magnetic locking is know as "Cogging" in 3 phase squirrel cage induction motor. In order to avoid this problem, the rotor slots housing the conductors are skewed by an angle of 5 degrees over the surface.
Why are the rotor bars of a squirrel cage induction motor usually slanted i.e. not entirely parallel with the shaft?
The squirrel cage is skewed so that the force applied to the rotor it continuous. If they were straight then the force would be jerky, as whole of the bar is cutting the magnetic field lines at the same time. With the bars skewed the amount of the bar cutting the field line grows continuously and the next bar starts cutting the field lines as the first finishes. also, slots are skewed to get uniform torque ,reduce the magnetic locking (also called COGGING EFFECT) between stator and rotor,and thirdly to reduce the magnetic humming noise during running condition
Why rotor slots is more than stator slots in induction motor?
rotor slot more. it is to get a large rotor inductance value of inductance the stator windings
What are slots in dc generator?
Slots are teeth shaped portions made on outer periphery of rotor and coils are placed in these slots.
What is the difference between squirrel cage and slip ring induction motor?
the difference is that squirl cage the rotor is short circuited while it is on operation and out of operation while the rotor of the bother one is connected to nexternal circuit to reduce the starting intial current
Define gap contraction factor for slots?
It is nothing but the effect of flux which is reduced slightly due to fringing effect. it depends on the material used for the stator and rotor design. as well as shape of the slots.
Why is the squirrel cage motor used in most industry?
because the squirrel cage induction motor is cheaper and high starting performance is not required.
What is construction of cage induction motor?
The rotor is manufactured from a stack of circular silicon-steel lamination clamped together around a shaft, with open or closed slots running along the length of the rotor through which the rotor conductors ('bars') pass. The rotors are then interconnected at opposite ends with conducting end-rings. In some cases, the rotor bars are poured into the (enclosed) slots as molten metal. If the bars were visible, they would resemble a gerbil's exercise wheel.
Why rotor of an induction motor has slots around periphery filled with copper or aluminium?
The slots in the rotor of an induction motor are filled with copper or aluminum because those copper or aluminum filled slots are conductors. They constitute multiple one-turn transformers, setting up an induced magnetic field, induced from the field windings, that creates a differential magnetic flux, i.e. a torque, that causes the rotor to turn.This has little to do with the fact that the field windings are pulsing from the AC current, because the rotor "windings" are pulsing in turn - what is happening is that the rotor and field "windings" attract or repel each other as a function of their distance from each other, which is related to slippage induced by torque.
What is inductor alternator?
The armature and the field windings of an inductor alternator are both accommodated in the stator. The three phase ac armature windings are distributed in small slots and the dc field windings are concentrated in two slots in the stator. Each field coil spans half the total number of stator slots. Armature coils are connected in star and field coils are connected in series. The rotor resembles a cogged wheel, with no winding. The core of the stator, which is completely embraced by the field coils, will retain a residual magnetism if excited once. When the rotor is rotated, the passage of the rotor teeth alternatively under the field offers a varying reluctance path for the flux produced by the field coils. This flux, which varies periodically, links with the armature coils and induces an emf in them. The frequency of the induced emf depends on the speed of the rotor. The magnitude depends on the speed of the rotor as well as on the level of excitation. The armature and the field windings of an inductor alternator are both accommodated in the stator. The three phase ac armature windings are distributed in small slots and the dc field windings are concentrated in two slots in the stator. Each field coil spans half the total number of stator slots. Armature coils are connected in star and field coils are connected in series. The rotor resembles a cogged wheel, with no winding. The core of the stator, which is completely embraced by the field coils, will retain a residual magnetism if excited once. When the rotor is rotated, the passage of the rotor teeth alternatively under the field offers a varying reluctance path for the flux produced by the field coils. This flux, which varies periodically, links with the armature coils and induces an emf in them. The frequency of the induced emf depends on the speed of the rotor. The magnitude depends on the speed of the rotor as well as on the level of excitation.
What is the need for semiclosed slots in squirrel cage induction motor?
By using semi closed slots , we can increase the air gap thus by reducing magnetizing current & pulsation of flux in individual teeth by reducing tooth loss. That's why the efficiency is also increased.Mahavirc.v.raman college of engg.Electrical department
What is cogging and crawling in case of 3 phase induction machines?
CoggingInduction motors have a series of slots in the stator and in the rotor. These slots should not be equal in number because if they are, there is a good chance that the motor will not start at all due to a characteristic known as cogging. The slots will align like a stepper motor. For this reason, there are an unequal number of slots in the rotor and in the stator, but there can still be situations where the slot frequencies coincide with harmonic frequencies and this can cause torque modulations. The slots are skewed to keep an overlap on all slots to reduce this problem.CrawlingAnother characteristic of induction motors, is crawling. There are harmonic fluxes developed in the gap due to the magnetics of the motor. These harmonics create additional torque fields. A common problem is with the seventh harmonic where the seventh harmonic creates a forward rotating torque field at one seventh of the synchronous speed. There will be a maximum torque just below 1/7 Ns and if this is high enough, the net torque can be higher than the torque due to the line frequency where at 1/7 Ns, the slip is high. This can cause the motor to crawl at just below 1/7 synchronous speed. There is another crawl speed at 1/13 Ns.
