Talk:AC motor

Topics from 2007

Dremel rotary motors

How can these universal motors achieve high speed? — Preceding unsigned comment added by Ericg33 (talk • contribs) 09:58, 8 February 2011 (UTC)

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)

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)

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)

Topics from 2008

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)

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)

Three Phase AC Induction Motors

I request that the second paragraph in this section should be rewritten by a qualified individual. Apart from the language, which seems clunky and inexpert and features excessive use of brackets, there is something that I find confusing here:

Through electromagnetic induction, the time changing and reversing (alternating in direction polyphase currents) rotating magnetic field induces a time changing and reversing (alternating in direction)current in the conductors in the rotor; this sets up a time changing and counterbalancing moving electromagnetic field that causes the rotor to turn in the direction the field is rotating. The rotor always moves (rotates) slightly behind the phase peak of the primary magnetic field of the stator and is thus always moving slower than the rotating magnetic field produced by the polyphase electrical supply.

In the last sentence the word thus seems misplaced. The fact that there is a phase difference does not mean that the frequencies are necessarily different. It seems that the difference in stator and rotor frequencies must be due to another factor not described here.

PlantTrees (talk) 18:09, 19 August 2008 (UTC)

I think action is long overdue on your request for clarity! This isn't my area of expertise, but I think my knowledge extends to improving this one. Further improvements welcomed!

Cooperised (talk) 14:57, 4 June 2009 (UTC)

Outside stator?

The introductory paragraph states the an AC motor has an outer stator and inner rotor. I can't see why this needs to be true. DC motors exist with the stator on the inside and the rotor on the outside - see bicycle hub motors as an example. While most AC motors are as described, is there any reason to state this as the way the motors must be? --Michael Daly (talk) 17:39, 19 September 2008 (UTC)

Retrofit topic year headers

27-Sep-2008: I have added subheaders above as "Topics from 2007" (etc.) to emphasize the dates of topics in the talk-page. Older topics might still apply, but using the year headers helps to focus on more current issues as well. Afterward, I moved the rotor-types topic into date order for May 2008. -Wikid77 (talk) 03:39, 27 September 2008 (UTC)

Cleanup September 2008

27-Sep-2008: The article "AC motor" still has several areas where the text is not complete sentences, just sentence fragments, but the intent of the wording is not clear. I will try to adjust those fragments to become whole sentences. In general, the level of wording is somewhat complex, and more diagrams or examples could be added to avoid a "too-technical" level of information, for general readers. -Wikid77 (talk) 03:39, 27 September 2008 (UTC)

No evidence that Tesla identified or applied the magnetic rotating field before 1888

Historical proves that Tesla "identified" (weird verb, usually exploited by someone who want to prove something without evidence. Usually inventors just publish, create, patent...)are non existent. The fact is that Tesla spent most of its energies by trying to create a mith of himself through letters or memorials. He was simply obsessed not to be recognised as the first having invented or applied or thought something......Tesla was aware that Ferraris had created induction motors in 1885,three years before him (1885 Ferraris's models still exist where are those created before 1888 by Tesla?), and just put about the history of the idea conceived in 1882. No priority on a discovery can be given to Tesla or to anyone else just refering to memorials based merely on owns testimonies without any rigorous evidence. —Preceding unsigned comment added by 193.136.94.218 (talk) 22:44, 7 September 2009 (UTC)

Topics from 2010

Pictures please!

Some (animated) pictures of how an AC motor works would be nice.

where is the picture of the AC MOTOR (section) ? 92.234.245.195 16:51, 18 July 2010 (UTC)

Suggest merging content with similar page Induction_motor

There is a lot of duplicated content on this page that could be merged with the Induction_motor page. This would the leave the page with an unbalanced content as it would detail AC motors in general but not induction motors specificity. Ideas anyone?

why three phase motor star point is not grounded

The star point is at ground potential and therefore no current would pass between it and ground anyway--in pure theory. In practice, motor windings differ slightly in reactance, resistance, losses, etc.; line potentials are not symmetrical, congruent, precisely phased, etc.; loads are impulsive, not constant, etc.; and so the star point wanders around just off from ground potential and any current to ground would represent a conversion of work to heat (loss) and tend to unbalance the rotor, cause vibrations, etc. Mouselb (talk) 07:19, 14 July 2012 (UTC)

Topics from 2011

Induction motor speed summary

The top summary section currently says "The first type is the induction motor, which only runs slightly slower or faster than the supply frequency." I'm not an expert on motors, but I've been talking to a bunch trying to reconcile this sentence with reality. Induction motors like common house fans can run happily at many speeds not related to 60 Hz. Moreover, OR undeniably shows that a simple dimmer circuit in front of such a fan gives one nearly arbitrary control over the motor's speed, which is clearly not linked to the supply frequency. This might not be a great design, but it's what happens. After talking to a number of experts I changed that sentence to "The first type is the induction motor, which operates at a speed which varies with load." Andy Dingley reverted this change calling it "Unhelpful and highly misleading change." Having spent several days trying to understand the sentence as written, I believe it is misleading and certainly doesn't help me. Can somebody provide a better summary of how fast induction motors actually run? Leopd (talk) 19:40, 16 August 2011 (UTC)

"I'm not an expert on motors" Then it's generally best to be reading an encyclopedia, not changing it.

"Induction motors like common house fans can run happily at many speeds " Not in the scope of this article they can't. I don't know what sort of house fan you have, so I don't know what sort of motor it uses. I do know though that the simple form of induction motor, as described here, only runs at one speed. There are other kinds of motor too, and there are also more complex induction motors that can run at different speeds. Neither of these are relevant or useful to explaining the basic operation of an induction motor though, which is one reason why a house fan wouldbe a poor choice for an example.

"OR undeniably shows that a simple dimmer circuit in front of such a fan gives one nearly arbitrary control over the motor's speed"

Then your OR needs to try it again with something that uses an induction motor, not a universal motor.

Induction motors run at a speed close to the line frequency. It is not the same as line frequency, as there must also be some slip: a differential between the speed of the rotating field in the stator and the rotation of the rotor. It is this slip, and the resultant relative movement, that provides the changing field needed to induce a current in the rotor armature (the squirrel cage), hence the name "induction motor".

The amount of slip varies with load, which does literally mean that "the speed varies with load". However this is far from the speed variation under load that's shown by a DC motor. In particular, induction motors aren't designed to run under load conditions of excessive slip (i.e. a significant variation in speed) and they'll suffer from armature overheating before they do.

The point about prime numbers is also a commonplace fact. Many rotating machines use prime numbers, whether they're electrical machines or gearboxes. Most rotating machines don't rotate in isolation, they rotate against something or alongside something. If both of these components have a number of poles or teeth (whether the same or different) and the highest common factor of these two numbers is quite high (worst case is that they're the same), then there will be a beat frequency between the two of them. The strength of this beat (not the frequency) depends on the factorisation between these two numbers: the more poles that pass simultaneously, the stronger (and usually worse) it will be. Making the two pole / tooth counts relatively prime avoids this. It only requires one of them to be a prime number or a low multiple of one. As the operation of an induction motor doesn't depend on having matching numbers of poles, having a prime (or twice a prime) number of bars in the squirrel cage rotor gives a more even output torque, without the problem of beats. Andy Dingley (talk) 22:54, 16 August 2011 (UTC)

I think the biggest flaw with the sentence as written is that it refers to the supply frequency, not a ratio of the supply frequency. I don't think all induction motors run near 3600 rpm, as the article implies. The implication is reinforced by the juxtaposition with the summary description of synchronous motors which can run at a sub-multiple of the supply frequency. Can we agree that this part could be improved? Leopd (talk) 00:30, 17 August 2011 (UTC)

IEEE says "ac" and "dc" should be lower case.

Any objections to conforming with IEEE on this? — Preceding unsigned comment added by 63.195.83.157 (talk) 05:00, 25 October 2011 (UTC)

How does pure resistance cause a "small phase shift" in any circuit and affect anything but the quiescent point in a reactive circuit?

See: Split-phase induction motor, inductors and resistors in whatever arrangement will always be at identical phase. Mouselb (talk) Mouselb (talk) 07:25, 14 July 2012 (UTC)

Squirrel-cage motors used in virtually all washing machines, dishwashers, etc.? Really?

The main motors I've encountered in washing machines are universal motors, with smaller motors (with permanent magnet rotors) used in the pumps. Mspritch (talk) 22:46, 30 July 2012 (UTC)

AC motor gaps and checklist

AC machines	Induction motor Polyphase SCIM WRIM Single‑phase Shaded-pole motor Split‑phase Capacitor start motor Resistance start motor PM capacitor start motor Synchronous motor WRSM PM Axial/disk PM motor Radial Interior magnet rotor Trapezoidal BLDM PMSM Surface magnet rotor Trapezoidal BLDM PMSM SyRM VRM SRM Stepper motor Special motors Universal motor Linear motor Transverse flux motor Modular PM motor

Legend

• BLDM - Brushless DC electric motor
• PM - Permanent magnet
• PMSM - Permanent magnet synchronous motor
• SCIM - Squirrel-cage induction motor
• SRM - Switched reluctance motor
• SyRM - Synchronous reluctance motor
• VRM - Variable reluctance motor
• WRIM - Wound-rotor induction motor
• WRSM - Wound-rotor synchronous motor

This is collage from

• AC motor
• B. K. Bose's book Power Electronics and Motor Drives : Advances and Trends fig. 6.1, Classification of machines for drives, p. 328.
• Kay Haymeyer's AC Machines I course notes at http://materialy.itc.pw.edu.pl/zpnis/electric_machines_I/ForStudents/Script_EMIHanneberger.pdfCblambert (talk) 21:52, 10 February 2013 (UTC)

Tree updated in line with revised 'electric motors' templateCblambert (talk) 03:03, 12 February 2013 (UTC)

Reconciling page view stats for AC motor with Transformer and with AC motor & related articles

Here are the page view stats for Transformer with various motor/related articles:

• Transformer has been viewed 552300 times in the last 90 days. This article ranked 1882 in traffic on en.wikipedia.org.

Electric_motor has been viewed 360233 times in the last 90 days. This article ranked 4713 in traffic on en.wikipedia.org. Rest of articles shwo pages viewed in the last 90 days.

• AC motor - 97,042
• Induction motor - 193,846
• DC motor - 116,975
• Synchronous motor - 71,767
• Rotor (electric) - 12,456
• Stator - 39,751
• Brushless DC electric motor - 109,517!!!
• Stepper motor - 145,219!!!!!!!!!
• Shaded-pole motor - 12,383
• Switched reluctance motor - 16,048
• Repulsion motor - 5,032

This does not make it clear to me what if anything might be done about this. But here is some observations:

• It is interesting that there are twice as many hits for Induction motor as for AC motor, which suggests that history section for latter should be combined with the former, at least initially.
• No need to spend too much AC motor effort for Brushless DC electric motor and Stepper motor.
• Repulsion motor should be moved to AC motor.
• It is suggested that AC motor be transformed into an 'AC machines' article.
• Theoretical treatment for AC motor could be vastly beefed up, à la Transformer.
• Rotor (electric) & Stator could then be absorbed into 'AC machines' article.
• In general, Transformer andAC motor should mirror each other in terms of only dealing with general aspects, transformer and motor types not being included in these two overview articles.Cblambert (talk) 00:53, 11 February 2013 (UTC)

Added stats for Electric motor. All the reason to say that major pruning of these overlapping articles would seem to be in order.Cblambert (talk) 18:54, 11 February 2013 (UTC)

I have slightly changed the wording and explained why induction motor is also called asynchronous motor. There was just one time the word "asynchronous" to be found on this page. It is just a small change but I think it lets people have a better start.Sonk11 (talk) 13:13, 9 April 2013 (UTC)

Induction motor formula

Is there any particular reason the formula for speed of an induction motor is given as Ns=120F/p, rather than simply Ns=2F/p?

I know it is to covert the mains frequency from cycles per second to revolutions per minute, with it specifying the Ns as revolutions per minute, but it has no specifications on the mains supply frequency and simply assumes it is in cycles per second.

I think it would be better to either remove the 120 leaving it as 2, or introduce it as 2*60 seconds per minute. As it is now, it gives an incorrect forumala where if you sub in values of 2 poles per winding and 50 Hz, you get a frequency of 3000 Hz.

Does anyone have any comments or would I be fine to change it?Black.jeff (talk) 20:58, 8 November 2016 (UTC)

It's probably wrong. This article is perennially getting broken by Indian engineering college students who keep changing it incorrectly (the other one is counting poles vs. pole pairs). You obviously understand the issue, so do whatever you think is clearest. Andy Dingley (talk) 21:20, 8 November 2016 (UTC)

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Neodymium abbreviated as Nd

The wiki text “{{neodymium}}” makes an automatic abbreviation of neodymium into Nd. This makes the text hard to read IMHO. Can it be changed? — Preceding unsigned comment added by 94.254.42.20 (talk) 08:53, 21 September 2018 (UTC)

Someone has now fixed this and the template is being deleted. User:GKFX^talk 19:24, 2 December 2021 (UTC)

Why no mention of motor efficiency?

Could there be something written about the relative efficiency of the various types of motors? — Preceding unsigned comment added by 198.2.107.38 (talk) 02:12, 24 July 2019 (UTC)