Talk:Electric motor

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Old threads moved to archive[edit]

The talk page was getting quite long even by modern Wikipedia standards. The older threads are at Talk:Electric motor/Archive 1 --Wtshymanski (talk) 21:47, 15 October 2009 (UTC)[reply]

Last few years moved to Archive 2. --Wtshymanski (talk) 05:01, 1 May 2020 (UTC)[reply]

Superfluous refs[edit]

Some of the points in this piece have >10 references. This makes no sense. Unless a point is controversial, a single secondary source is all that is necessary. I encourage involved editors to clean this up. Readers will thank us. Lfstevens (talk) 22:31, 14 June 2018 (UTC)[reply]

Request for some specific statements : Electric Motor Engineers, Help![edit]

Regarding permanent magnet motors:

I believe that the torque-per-volt/amp/watt is dependent on the BHMax of the magnets used. Is that true?
If true, then permanent motors have limitations on "small size" and "energy efficiency" based on the composition of their magnets.
If that is true, then for size and energy efficiency, NIB >> SmCo >> Alnico >> Ferrite >> Soft Iron
If that is true, are there approximations or upper limits for the energy efficiency given the available magnetic material?

The delivered torque or size is clearly dependent on many other factors (nature and materials of the windings, nature and materials of the electromagnets and cores, gearing, internal/external stator/rotors, etc.) but I expect some things might be "rules of thumb" for motor engineers Clear, declarative sentences, or a nice table, might be nice:

Characteristics of PM Motors for given PM materials
all values are approximations
Material	BHMax	Typical Energy efficiency (J_kinetic vs J_emf)	Typical Space efficiency (M³ vs J_emf)
NIB	30-35	???	???
SmCo	20-25	???	???
AlNiCo	5-6	???	???
SrFe	...	...	...
BaFe	...	...	...
Fe	...	...	...

Any in-the-know folks want to chime in?

Riventree (talk) 11:50, 11 June 2020 (UTC)[reply]

Read “Manufacturing of Advanced Alnico Magnets for Energy Efficient Traction Drive Motors CRADA Final Report” at OSTI.gov and keep in mind that the rare earth magnets in your table are much more fragile than AlNiCo. A lot of people have a lot of money invested in finding compact low mass high efficiency electric motors. There is no shortage of high efficiency 3 phase AC motors and the volume to mass and HP ratio is more favorable at higher power than permanent magnet motors are useful for. Large DC motors are also quite efficient, by large I mean a 1 hour continuous rating well over 100HP, for large motors a short time rating is typically close to 2x. PolychromePlatypus (talk) 01:18, 26 July 2022 (UTC)[reply]

Electric Motor-Driven Systems[edit]

I am looking for inputs. The the term «Electric Motor-Driven Systems» seems to me a concise and important concept in the global analysis of energy technically, economically and environmentally. Do you also think it makes sense to create an article with this lemma? Or would you incorporate it somewhere in an existing article, and if so, where? Sources: https://www.energiestiftung.ch/files/downloads/energiethemen-energieeffizienz-industriegewerbe/ee_for_electricsystems-2-.pdf https://www.iea.org/reports/energy-efficiency-policy-opportunities-for-electric-motor-driven-systems Repinrepin (talk) 13:08, 15 September 2020 (UTC)[reply]

No: What would be the purpose of the proposed article? Since an electric motor driven system could be anything from a wristwatch to a warship, there doesn't seem to be much of an organizing principle to go on for an article. --Wtshymanski (talk) 19:19, 18 September 2020 (UTC)[reply]

No: Way too broad and diffuse in scope for a separate article. An "Applications" section in this article would suffice. --Chetvorno^TALK 19:32, 18 September 2020 (UTC)[reply]

Yes: I like the concept. The key point is that there are energy savings opportunities at the system level that are much larger than the 10 to 20% efficiency gain that might be possible with improving motors. There are references that address that systematically. Ccrrccrr (talk) 01:31, 19 September 2020 (UTC)[reply]

Except that the title of the proposed article is not "Energy savings in electric motor-driven systems", it is "Electric motor-driven systems". So the topic of energy savings would just be a tiny section buried in a huge, diffuse article covering general information about all systems incorporating electric motors. --Chetvorno^TALK 06:15, 19 September 2020 (UTC)[reply]

That's a good point. I like the idea of working on the title further better than the idea of "a huge diffuse article covering general information about all systems incorporating electric motors." The latter would be a terrible idea.Ccrrccrr (talk) 14:55, 22 September 2020 (UTC)[reply]

Why does the topic of energy savings in electric motors, which clearly belongs in this article, require a separate article, which will entail a lot of redundant explanation, and make it more difficult for readers to find? One more section in this article will not increase its size much. If it is decided that it will not fit in this article, we also have Energy efficiency, Efficient energy use, Electrical efficiency, Energy conversion efficiency, Energy efficiency in transport and Environmental impact of electricity generation, to put it in. --Chetvorno^TALK 18:09, 22 September 2020 (UTC)[reply]

No: It is silly to separate motor from motor driven system. What is the point of motor if it isn't connected to a motor driven system.Constant314 (talk) 03:28, 21 September 2020 (UTC)[reply]

Wrong: An electric motor is always connected to a system, even in the absence of external shaft loading. Rotating machines are used to stabilize an AC power system subject to transient disruptions and to supply local VARS to correct the local power factor. The machine's angular momentum isn't usually supplemented by a flywheel. (c.f. synchronous machine, wound rotor, variable excitation) The first step to wisdom is knowing what you don't know. That fact that you don't know something doesn't mean much. It only means you don't know. PolychromePlatypus (talk) 18:16, 23 July 2022 (UTC)[reply]

No: per WP:UCRN. Wikipedia is not written in academic/bureaucrat-ease. Fountains of Bryn Mawr (talk) 11:56, 21 September 2020 (UTC)[reply]

Yes: Wikipedia is written to be as accessible as possible. The proposed title and topic description are jargon loaded and likely to inspire more, re-consider those. In general terms an article about the fiscal and energy economics of electric motors and rotating machines in general would be useful. The topic is of increasing importance as energy continues to focus on electrical distribution. The topic is touched on in many places and there's a lot of good work out there that's not very accessible. A good article pulling good sources together and putting it in a digestible form would be a service. Wikipedia is a well suited to assembling available information, but that's all the value it can add, if seeing it all in one place leads to an obvious conclusion but there isn't a source for it, just let the readers reach the same conclusion on their own. I would suggest using a balance of sources Industry, government, and academic and be wary that however neutral the tone of the presentation, everyone has a point of view. When the sources diverge, don't select one you think is right or virtuous, describe both in the context of the differences in the underlying methodology. PolychromePlatypus (talk) 19:31, 23 July 2022 (UTC)[reply]

@PolychromePlatypus: But that would be a separate proposal. Repinrepin is not proposing an article on Energy economics of electric motors, he is proposing one called Electric motor-driven systems. That would be gynormous. --Chetvorno^TALK 22:33, 23 July 2022 (UTC)[reply]

Yes, quite true. My experience is that telling people with energy and enthusiasm not to do something is less effective than suggesting something that would be more desirable. The same applies to owning a dog, but don’t suggest, it confuses the dog. PolychromePlatypus (talk) 01:35, 26 July 2022 (UTC)[reply]

Small clarification needed in Electromagnetism Section under Goodness Factor[edit]

In the Goodness Factor formula, the symbol "Sigma" is not defined, and I am not qualified to suggest its definition.74.195.124.209 (talk) 12:49, 26 February 2021 (UTC)[reply]

Annual production[edit]

"In 2022, electric motor sales were estimated to be 800 million units,..."

This seems like a low estimate to me. Apparently, about 80 million motor vehicles were produced in 2021 [1], and I think even internal-combustion-powered vehicles would contain quite a few electric motors (starter motor, windscreen wipers, door winders ...) Then we have electric household appliances (vacuum cleaners, blenders, electric mowers, ...), power tools, toys, and I imagine a lot of industrial equipment. I know the 800 million units has a source. ghouston (talk) 02:11, 3 June 2022 (UTC)[reply]

800 million sounds like AC machines 1/4 HP and larger. Its too low just starting with global automobile production and multiplying by 10 for the average number of small electric motors in an automobile for the starter, engine cooling (2), wipers, windshield washer, idle control, antilock braking, defog/heat/vent cabin blower, window operators (4), door locks (5), evaporative emissions control (2) etc. in the USA, EU, Japan, etc. the number is around 18. Even the most basic lowest cost designs for emerging markets are not less than 4 (start, wipe, wash, cabin blower). PolychromePlatypus (talk) 17:25, 30 July 2022 (UTC)[reply]

Power factor, gap, magnetic circuit[edit]

An editor who self-evidently has no relevant expertise reverted an edit correcting the ignorant assertion that the air gap in an electric motor causes low power factor and reduces efficiency. This well intended person also doesn't know that windage is a non-trivial efficiency factor. What hobbyists learn from tinkering with permanent magnet DC motors in toys tends to give them these ideas, the magnetic path in a toy's motor is dictated by cost, size, and weight in that order, performance is almost an afterthought. The same impressions aren't noticeably wrong tinkering with fractional horsepower universal motors and shaded pole bathroom blower motors. They aren't actually correct for any AC machine and unless they have some experience with large AC machines they never find out that they're wrong.

I'm not interested in arguing with a fool or writing a primer here to persuade an editor who doesn't know what they're talking about that someone with a Ph.D. E.E. who designed hundreds of magnetic circuits during a long career does know what they're talking about.

I'm here to say that if you don't have the relevant expertise and you aren't wiling to do enough research you're making Wikipedia what it is today - the blind leading the blind. Have A Nice Day PolychromePlatypus (talk) 17:58, 23 July 2022 (UTC)[reply]