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When rotor bars are made to run parallel with stator , the
torque rises & falls correspondingly causing more
pulsations. This is termed as cogging in other qords
magnatic locking. This is reduced by making the rotor bars
run at an angle to the stator ie crawling in order to make
the torque uniform.
Crawling on the other hand signifies running of motor at
almost one seventh of the rated speed due to interference
of seventh harmonics.
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Crawling in induction motor is caused by?
Crawling is caused by harmonics effects on the motors rotating magnetic field. If harmonic levels are high enough they can become the dominating factor in the rotating magnetic field causing the motor to run at a much lower speed than designed. http://www2.sea.siemens.com/NR/rdonlyres/4058E086-2AFD-4C47-B9B1-0FCF4428FA39/0/MAGNETICNOISEININDUCTIONMOTORS.pdf
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
What is a slip ring connection?
Here is the list of actual exam or homework questions the Asker wishes to have someone write the answers for him to copy without looking them up for himself: : 1) What is a slit ring and a slip ring in electrical ... (machines?) : 2) mention the application of the method of connection in brief : 3) what is the phase type (1phase, 3phase) and explain why not using 2phase : 4) what is cogging and hunting? explain briefly : 5) what is the difference between neutral and earth? explain briefly
Why there are less Female electrical engineers?
As a senior female electrical engineering student - the only one in a class of 30, I've thought quite alot about why I'm still taking engineering, and why there aren't more females like me doing what I'm doing. Engineering is logical. It's about definite results and profit. It's about getting "the right answer" to the question, because if a gadget doesn't work, it doesn't work. There isn't any ambiguousness to it like in the social world. In addition, it's not an absolute requirement in engineering to have verbal and social skills. For women who aren't that comfortable socially, have a good aptitude in science in math, and either don't mind or are almost unaware that they the minority, engineering can be a perfect fit. But there aren't too many women like that. And the ones who are, tend to take things like medicine and biology because they appear to help humanity more directly than engineering. I don't know many women who grew up taking apart televisions and making hot wheels go "vroom, vroom", around the carpet. Even if a woman does choose engineering as a career, she is going up against men with whom engineering is alot like breathing, the interest has been there since they started crawling. With women, interest in engineering as a career is more likely to come in secondary school or beyond - because they excel in academics. And those women, like myself, have alot to catch up on. Of course, I'm not saying that women don't have the aptitude for engineering, it's just that engineering is portrayed as cold and hard and efficient, and although women in general may appreciate these things, the average woman would rather be in a major that is more social, requires emotional intelligence, and clearly has a positive impact on society.
What is cogging torque?
Cogging torque is due to the slotting, and pulsation torque is due to the space harmonics, and both must be reduced for best perfomance of the machine, so it's a negative influence.
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.
What is cogging effect?
The cogging effect is the attraction between the magnets and the stator poles when at rest; this attraction and cogging is easily felt when trying to turn an electric motor by hand. A common misconception is that cogging is caused by the copper coils; however, this is not the case. An unequal attraction between the magnets and the stator results in the rotors reluctance to turn. The magnets sit comfortably at rest over a pole, and when the rotor is turned, they must move over an air gap before reaching the next pole. The rotor resists the turning, the magnets attempting to stay bonded to the current poles, until just over halfway through the air gap, where the attraction to the next pole is stronger than that of the previous pole, resulting in a "clunking" or jumping effect at low RPM (such as when trying to turn by hand). This is the cogging effect, resulting in a large torque required to begin rotation. The cogging effect is the attraction between the magnets and the stator poles when at rest; this attraction and cogging is easily felt when trying to turn an electric motor by hand. A common misconception is that cogging is caused by the copper coils; however, this is not the case. An unequal attraction between the magnets and the stator results in the rotors reluctance to turn. The magnets sit comfortably at rest over a pole, and when the rotor is turned, they must move over an air gap before reaching the next pole. The rotor resists the turning, the magnets attempting to stay bonded to the current poles, until just over halfway through the air gap, where the attraction to the next pole is stronger than that of the previous pole, resulting in a "clunking" or jumping effect at low RPM (such as when trying to turn by hand). This is the cogging effect, resulting in a large torque required to begin rotation.
When was The Crawling Distance created?
The Crawling Distance was created in 2009.
When was The Crawling Hand created?
The Crawling Hand was created in 1963.
When was The Crawling Chaos created?
The Crawling Chaos was created in 1921.
What is the duration of The Crawling Hand?
The duration of The Crawling Hand is 1.48 hours.
Is camel crawling?
No, crawling is movement low to the ground-usually insects, etc.
When was Crawling in the Dark created?
Crawling in the Dark was created on 2002-04-02.
How do you get crawling hand pet in runescape?
Kill Crawling Hands until they drop a hand, pick it up and do soul wars until you get enough points for a pet crawling hand, with the hand in your inventory buy it and you will have a pet crawling hand.
Are dinosaurs crawling?
no there not
When was Hungerford's crawling water beetle created?
Hungerford's crawling water beetle was created in 1954.
