ATAR Notes: Forum
HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Physics => Topic started by: nickglyn on October 24, 2016, 05:45:21 pm
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With squirrel cage induction motors, do they run on single phase, or three phase power? Or does this not exactly matter? And also, how exactly does the magnetic field in the stator rotate?
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With squirrel cage induction motors, do they run on single phase, or three phase power? Or does this not exactly matter? And also, how exactly does the magnetic field in the stator rotate?
It doesn't matter. They're different.
They don't run based off current. They run on the principle of electromagnetic induction.
We produce a rotating magnetic field in an AC induction motor. This could be I don't know. Maybe another motor or something. Maybe a solenoid (preferably).
But the point is, the rotating magnetic field is what's behind this application of electromagnetic induction.
(I'm busy right now so I'll let someone else give you the full explanation. It's also applying Lenz's law with the principle of electromagnetic induction in full.)
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Yes yes I understand that, but what I mean to ask is what type of power is fed into the stator in order to cause the rotating magnetic field? Will it still rotate even if single phase power is used?
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Yes yes I understand that, but what I mean to ask is what type of power is fed into the stator in order to cause the rotating magnetic field? Will it still rotate even if single phase power is used?
Single phase does exist but it isn't as powerful as three-phase.
But yeah, it's a synchronised AC current I believe.
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Yes yes I understand that, but what I mean to ask is what type of power is fed into the stator in order to cause the rotating magnetic field? Will it still rotate even if single phase power is used?
Hey Nickglyn!
The purpose of having a motor is so that the rotor can rotate continuously. Sure we can use single phase power and still achieve a similar effect, but the rotation of the rotor would not be continuous because there is a short pause between each change in polarity for a single phase current supply. So for instance changing from positive to negative would take 1 second then the rotor would stop rotating for one second until the next change in polarity (and hence magnetic field) occurs.
The purpose of us having a three-phase current supply is so that the rotation can be done seamlessly, i.e. without any stopping. When one pair of electromagnets stop acting as north and south poles, there will immediately be another phase of current being supplied to another pair of electromagnets created north and south poles. In this way a rotating magnetic field is achieved.
So yes we can use single phase but it wouldnt suit out purpose because it cannot facilitate the smooth and continuous rotation of the rotor.
Best Regards
Happy Physics Land
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Okay awesome. So for example, if they ask us in our exam to outline the structure of an AC induction motor and how it works, would we say "three phase power is supplied to the windings inside the stator, thus creating a rotating magnetic field"? Or just say "a current is supplied to the windings blah blah"?
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Okay awesome. So for example, if they ask us in our exam to outline the structure of an AC induction motor and how it works, would we say "three phase power is supplied to the windings inside the stator, thus creating a rotating magnetic field"? Or just say "a current is supplied to the windings blah blah"?
Three phase is pretty essential to specify here in my opinion, so I'd say three phase current ;D
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Sweet, will do so. Thanks to all of you for the help! Also is it your birthday today Jamon? If so happy birthday! (hopefully i'm not delayed)
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Sweet, will do so. Thanks to all of you for the help! Also is it your birthday today Jamon? If so happy birthday! (hopefully i'm not delayed)
Aha thanks mate!! It is ;D