AC motor (3 Viewers)

[za]

5.1.1 - describe the main features of an AC electric motor.

if u are asked this question do u talk about the universal motor or the induction motor because thre features clearly differ.

 

[Xayma]

I would briefly discuss all three.

Universal
Synchronous
Induction.

There features differ although I think the induction motor might be addressed in a dot point of its own if it is don't worry about it.

 

[za]

synchronous?
havnt heard of that one.
i only know the ones in the jacaranda textbook.

 

[Xayma]

Synchronous, the one with the slip rings

 

[mr EaZy]

i would talk about the synchronous one

 

[Tommy_Lamp]

i dont talk about universal, just synchronous and induction because their the ones that are used most often

 

[za]

can the question be specific, ie specifying which type

or would it more likely be about ac motors in general

 

[d_elmo]

Help

would anyone be able to try and explain to me briefly how the AC motors work cause ive got a really dodgy teacher and he didnt explain a lot

 

[snoopwogg]

Well DC motors work by making sure there is a constant change in flux threading the rotating coils. Because the polarity of the coils is changed every halfturn, the forces on the respective sides of the coil are kept in the same sort of direction. In AC motors however, there is already a changing polarity in the coils, and hence a split ring, which reverses polarity, is no longer needed. Hence, to keep the forces on either side of the coil to keep moving in the same sort of direction, a constant contact is needed from the brushes on either side of the coil. Hope that clears it up a little. Its kinda hard to explain.

 

[mazza_728]

whats the difference between universal, synchronous and induction?

 

[Jase]

A(n?) universal motor is just the DC motor, and uses the commutator.

A synchronous motor uses slip rings and the normal AC motor style.

Where as induction motors are like the squirrel cage, or three phase AC motors.
It's like.. kinda self starting, where the magnetic field rotates, inducing an emf in the cage which sets up another magnetic field to move the rotor.

Actaully, technically, an induction motor can also be a synchronous motor i think, like when the magnetic field rotates in sync with the rotor.

 

[JayWalker]

I'll just add and make it look tidy

AC Induction Motor: AKA Squirrel Cage
No Slip Rings
Uses a changing magnetic field to induce eddy currents in the squirrel cage to create movement
[3rd Year Engineering]: Can rotate EITHER way...
Needs a starting motor

AC Normal Motor: AKA Synchronous
Uses Slip Rings, Coil, Magnetic field.. duh easy
Needs a resistor to start due to large back emf...

AC Motor (Universal)
umm.. I was sure that a universal AC motor was the same as synchronous...

 

[Constip8edSkunk]

universal motor has split rings so it can run on dc

 

[Xayma]

Universal motor does not have split rings .

Universal motor has a split ring commutator, plus the armature/magnets are wound in series so when the current reverses everything reverses and it spins in the same way even if it is only 1/4 of the way through.

 

[JayWalker]

Universal motor does not have split rings .

Universal motor has a split ring commutator,....

Just me or are you contradicting yourself?!

 

[mr EaZy]

is there a catch heere im not getting?

split rings and split ring commutator...........huh!

 

[JayWalker]

I thought they are same thing..
EEK!

Something I dont know!! I'm SCREWEEDD!!!!

 

[Xayma]

Yeah I thought you said slip rings never mind. But do refer to it as a split ring commutator.

It is easier to think of a universal motor as a DC motor with the electromagnets and armature wound in series than as a AC motor with a split ring commutator

 

[Jase]

ahahahh.. Damn.. So confusing.. Slip and Split...

 

[Xayma]

It wasn't helped that he put a plural. *shakes fist*