3phase induction? (1 Viewer)

[Premus]

i just saw something abt 3 phase induction motors?
i dont have a clue what it means....can u guys help me?

Thanks!

 

[Xayma]

3 Phase induction motors provide a constant torque, instead of alternating as the magnetic field changes strength.

3 Phase AC is where each phase is out by 60° ie if the first phase was 0, the next one would start at 60° followed by 120°.

 

[Premus]

what do u mean when u say... each "phase" is out by 60 degrees?
what exactly is a phase?
i dont quite understand

thanks

 

[Mithoric]

I that each phase was offset by 120 degrees? Seems I need to revise this pretty soon lol..

You should know what a phase is, have you graphed a sine wave? When two waves are in phase they they have their troughs and peeks at the same time, when they are out of phase their trough and peeks are at different times. In 3 phase power you have 3 currents going at different phases so it's like you have constant power, well it's fast enough to say you do have constant power really..

That's a crude explanation and I've have forgotten most of it lol, I think that's correct though.

 

[Xayma]

Yeah 3 phase is out by 120 degrees, opps.

Yes look at a sine wave, if one started at 0 degrees, one at 120 degrees and one at 240 degrees thats what 3 phase looks like.

 

[Steven12]

so does the 3 phase overlap onto each other so the Curvy line never reach the x axis?


and if so, what modification do you need to make on the generator?

 

[Xayma]

Add the voltages.

You have three generators if you look outside at power lines you will see multiple lines, 3 of those are for 3 phase and another earth line.

 

[Li0n]

Xayma man, you're getting the best revision by helping everyone. Most threads in chem, phys and ext-1 its Xayma to the rescue. Class...
A new approach to studying i say!

 

[Mithoric]

Don't you people do maths? :|

 

[Dash]

I remeber 3 phase motors being taken out of last years syllabus...

 

[grimreaper]

I remeber 3 phase motors being taken out of last years syllabus...

Yeah its certainly not directly in the syllabus now... but isnt it still related to an advantage of AC over DC? (ie that you can have 3 phase power)