Talk:AC motor

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Contents 1 Induction rotor types 2 Single-phase reversability and pole shading 3 Some discussion of ECM (Electronically Commutated Motor) is needed 4 Spam 5 Time constant in a two-phase asynchronous motor model

[edit] Induction rotor types

Discussion of squirel cage and wound induction rotors applies to both two and three-phase induction motors. These are useful sections but they were haphazardly dropped into the middle of the three-phase induction motor section and should be relocated.--Kvng (talk) 23:22, 28 May 2008 (UTC)

[edit] Single-phase reversability and pole shading

I don't see much discussion of reversal in single-phase motors. Generally single-phase motors can spin in either direction, and the actual starting direction is imposed by the starting coil. I believe the starting coil is a mounted few degrees off from the main coil (about 1/4th of the distance between two adjacent poles) so that it will induce a pull that biases the rotation to prefer one direction over the other. Reversing the polarity of the starting coil causes it to repel the rotor off in the other direction.

An induction motor that is turned on with only the main drive coil active can be hand-started to spin in either direction.

Meanwhile pole shading serves a similar purpose in very small and simple induction motors. The loop creates back-emf, which in turn sets up a weak biasing field to push the rotor in one direction only. Move the loop to the other side of the pole-face and the rotation will be reversed..

DMahalko 16:37, 10 September 2007 (UTC)

[edit] Some discussion of ECM (Electronically Commutated Motor) is needed

I suggest that the mention of ECM motors would make a useful inclusion here. —Preceding unsigned comment added by 69.156.117.69 (talk) 14:15, 21 December 2007 (UTC)

[edit] Spam

A link to electojects.com has been repeatedly added to Stepper motor, Electric motor and Brushless DC electric motor by Special:Contributions/217.53.109.235, Special:Contributions/82.201.156.201, Special:Contributions/217.53.107.168, Special:Contributions/217.53.16.164, and others.

The link in question is registered to Abdoh Ali Mohamed, Hay Swesri, Nasr City, Cairo, Egypt.[1]

I wonder if the four IP addresses listed above have any connection... Naw, couldn't be. [2][3][4][5] Egypt is a big country. Must be a coincidence.

I'm going to start patrolling wikipedia for any links to electojects.com or redirects to it and deleting them on sight. If they come back, I'll move to blacklist the address. Mdsummermsw (talk) 18:13, 28 December 2007 (UTC)

[edit] Time constant in a two-phase asynchronous motor model

J = moment of inertia
f = rotational friction coefficient

Two stator coils with each nst sinusoidal distributed windings
Two rotor coils with each nrot sinusoidal distributed windings
The angle between the coils is 90 degrees.
Two voltage sources applied on the stator, the angle between the voltages is 90 degrees.
Ust = effective value of each stator voltage
fst = stator frequency
ωst = 2πfst = angular stator frequency

Two external rotor resistances, each Rrot

Time constant = J/(f+2(Ust/ωst)^2/Rrot')
with Rrot'= Rrot(nst/nrot)^2
Starting from zero the motor speed remains constant after a time 5*(time constant).

Martin Segers (talk) 10:31, 5 January 2008 (UTC)