Hi guys and Sylvia, I'm rewinding a 4 pole compound motor so it is a series motor. It had two series fields and two shunt fields. Motor info 2hp, 28volt, 62 amps. It has been suggested that when I go from two fields to four that I should reduce the turn count on each field. My thinking (guess) is that I want to have the same inductance in four fields that I had in the original two fields. MikeK
total nonsence, you first need to count the turns on the old field, work out the total amp turns, and wind the new field to give the same total if you want the same full load speed. If you want less speed then you need more turns.
The old field has 17 turns on each field. For a total of 34 turns for two poles. These two fields were wired in parallel. When you say "work out the total amp turns"
Is that amp/turns per pole?
Since the two poles are is parallel that would be 1/2 times amp/turns or (.5 x amps)/17turns
And, what wiring scheme should I use: all in series, all in parallel, parallel two and put in series with the other parallel two?
Thanks for your input, MikeK
Amp-turns is amp-turns, not amps per turn.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Ya, I did that wrong, thanks. So is that amp-turns per pole? The two coils are in parallel so only 1/2 of the motor current would go through each coil. Thanks, MikeK
You'll reduce your RPM by half if that is the case.
two
tal
(.5
Your reply is confusing, firstly you said you had a compound motor so there should be two windings on each pole, series and shunt, you now seem to have only one. Secondly poles come in pairs, so a four pole motor has 2 pole pairs, opposite each other. Each pole pair needs to be considered as independent from the other pole pair. Magneticaly the poles of a pair are in series so the amp turns add up. eg: 17 turns at
1amp for each pole equals 34amp turns in total.
As long as they have equal resistance, current will be shared equally. This is equivalent to a series connection with half the turns of double-thick wire. They probably did this to save on the trouble of winding such beefy "wire".
Apparently, golf cart motors have single turns of rectangular copper going through the rotor and stator. Lots of amps.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
I'll try again. I have a compound 4 pole motor. Two of the poles are series fields with
17 turns, these two are wired in parallel. The other two poles are shunt fields and wound with many (100s) of turns. These are wired in series. Each pole has only one winding on it.This is correct.
But, these are in parallel so the current is divided, that would make it,
1/2amp x 17turns x 2 poles = 17 amp-turns. I think?Someone on a forum suggested that shunt fields commonly have equal amp-turns as the series field, so winding the new series fields the same as the original would give similar torque and rpm. So, if I wire the two new 17 turn poles in parallel and put those in series with original two 17 turn parallel poles I should have 1/2 amp through each pole of
17 turns, this equals 8.5 amp-turns. With 4 poles x 8.5 amp-turns I would end up with 34 amp-turns. I think this would be equal to the original series and shunt fields as far as amp-turns.What do you think? Thanks, MikeK
Ok, I see that now, it would increase the CEMF, slowing the motor. As I stated in another post, "someone on a forum suggested that shunt fields commonly have equal amp-turns as the series field" If I assume that, then I would get back closer to the original, if I wind the two new series fields the same as the original, put them in parallel as the original, and then wire these in series with the original. Feeble attempt to show that in ascii.
___l___ ( ( ( ( ( ( l______l ___l___ ( ( ( ( ( ( l______l l Hmm... Is this the same as putting two in series and parallel that with two more in series. ___l___ ( ( ( ( ( ( l l 1 1 ( ( ( ( ( ( l______l l Thanks for helping, MikeK
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.