Talk:Commutator (electric)

About the rating
Although there is decent amount of text there is a lot of redundancy so I think this article currently still qualifies as a stub. Specifically the last paragraph of the intro and the second paragraph of Composition of a Commutator are almost identical, but even much of the remaining text is largely a restatement of this same information on how they are constructed. More coverage should also be given to the longevity of the device, its history (both development and use), and something should be said about the efficiency of the device. -AndrewBuck 15:57, 27 March 2007 (UTC)

I rewrote most of the article partially addressing the issues mentioned above but I still think further attention is required. -AndrewBuck 14:14, 28 March 2007 (UTC)
 * Needs still more work. And references. I was going to say a commutator is a required feature of direct-current machines but I suppose there are homopolar machines. --Wtshymanski 02:22, 5 August 2007 (UTC)

Intro
"A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator."

no:
 * a motor/commutator based synchronous rectifier does not reverse the current - in fact it has no effect on the current in the motor at all.
 * a dc generator uses a commutator to avoid reversal of current, though its more complex of course.

"By reversing the current in the moving coil of a motor's armature, a steady rotating force torque is produced."

no. This would only be true if all the following were true (and they cant be): Tabby (talk) 02:12, 22 December 2007 (UTC)
 * communtator timing were perfect, with no gap and no overlap
 * Motor current remained absolutely constant, which is impossible since windings have inductance
 * Magnetic circuits were arranged to ensure constant torque despite changing rotational position.

Blinking GIF animation replacement
Not only is that flashing, pulsating, blinking GIF animation visually annoying to look at, but it is also fundamentally incorrect since it has a dead spot in the rotation, as the brushes cross the insulated midsection.

The simplest practical commutator has at least three segments, and the brushes must normally span two segments and short at least one winding, in order to maintain current flow in the other two windings.

I am going to see how hard it is to create a correct 3-segment animation, and with less annoying flickering. DMahalko (talk) 14:50, 19 May 2008 (UTC)


 * Actually, the simplest practical commutator has two segments connected to two windings on the armature. This arrangement is quite practical and works perfectly satisfactorily in a dynamo.  However, as noted, it is impractical in a motor because it would not be self starting.  An armature constructed this way is knowns as a "Siemens 'H' type". 86.150.65.44 (talk) 11:25, 9 August 2012 (UTC)

Agreed -- horrid animation that distracts greatly while trying to read and contemplate the information in the article. Wikisocko (talk) 23:40, 31 July 2009 (UTC)

Laboratory commutators
Can anyone identify Ruhmkorff and Pohl? Ruhmkorff is probably Heinrich Daniel Ruhmkorff. Pohl might be Robert Pohl but I think he is probably too late. If he was born in 1884, I think it unlikely his invention would have appeared in a text book as early as 1905. Biscuittin (talk) 16:11, 8 February 2009 (UTC)


 * I suspect it is Johann Ehrenfried Pohl. I will try to find out. Roberttherambler (talk) 00:55, 2 February 2017 (UTC)


 * No, it is Georg Friedrich Pohl (1788-1849). He is in German Wikipedia.  The relevant passage is "1825 erfand er das Gyrotrop" which Google translates as "In 1825 he invented the Gyrotrop". There seem to be three words for commutator in German: "Kommutator", "Gyrotrop" and "Stromwender". Stromwender actually translates as "power inverter" which would have a different meaning now from the meaning it had in 1825. Roberttherambler (talk) 16:24, 2 February 2017 (UTC)


 * I don't think this is yet solid enough to put in the article. Roberttherambler (talk) 22:53, 2 February 2017 (UTC)


 * I'm not convinced Gyrotrop is a commutator. See Gyrotropic. Roberttherambler (talk) 23:25, 2 February 2017 (UTC)

Electroconductive liquids commutator
Some infos about the use of ionic liquids and liquid metals and alloys (other than mercury) would be better to be added.--188.26.22.131 (talk) 17:02, 25 March 2011 (UTC)


 * Yes, sounds good. Some of the very first commutators were in fact built using mercury pools in laboratory experiments. This website lists several such devices.


 * http://www.sparkmuseum.com/MOTORS.HTM


 * DMahalko (talk) 20:08, 25 March 2011 (UTC)

It seems that mercury was the only liquid metal available at that time.--188.26.22.131 (talk) 11:36, 28 March 2011 (UTC)

Brushless commutator
Does the presence of liquid metals commutator in a motor make it a brushless motor?--86.125.151.236 (talk) 12:37, 26 March 2011 (UTC)

image
just an image ... may be useful. From .--J. D. Redding 02:23, 22 July 2011 (UTC)



Out of date information
I note that a few sections of this article are taken from a reference that is dated 1917. It may come as no surprise that there have been a few developments in motor and generator technology since that time. Although the field in a machine does skew with load, it is no longer necessary to position the brushes away from their normal position. Instead additional windings (called interpoles) are used to skew the field back to its original position (they are a sort of auxiliary series field winding positioned between the main field poles such as to oppose the skew). Though I have reference works, I do not have the facilities or the time to produce the revised diagrams (or even the ability to upload them) that would be required to rewrite this part of the article. 86.150.65.44 (talk) 13:11, 8 August 2012 (UTC)


 * The brush-shifting information is not out of date, and is relevant to devices without interpoles.


 * An additional section should be created that discusses interpoles, however my web searches for in-depth technical discussions and descriptions of interpoles are not turning up anything useful. If you can please cite any detailed technical documentation which includes diagrams and field patterns, that would be most helpful for improving this article.


 * DMahalko (talk) 19:54, 23 October 2012 (UTC)

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