Did you type that opposite of what you meant to say? I would think in a differential the shunt would weaken the series field, since that is the adjustable field.
I think you mean (through the shunt field)
I think you are saying put zero current through shunt to have a spinning wheel start and then for top speed turn shunt current to maximum.
Thanks, MikeK
Yes, I believe I have a differential compound motor, for a the reasons stated in the above posts.
You missed some of my earlier posts where I stated I only have three connections to the is motor A2, F1 and F2 .which I think is internally connected to A1. The drawing an the left side of this page is what I think I have. Although the polarity of the shunt may be reversed. I should have labeled coil A as the series field and coil B as the shunt Field.
I think we need to clear up this terminology series field and shunt field. The little knowledge I have would be from golfcart motors. Most are series field motors. They are wired so the field and the armature are in series. All the current that flows in the armature must also flow through the series field. They have large studs to the series field to go to a reverse switch to change rotation of the motor. In my motor the connections are all hardwired, sleaved and varnished in place so I can't really see what connects to what. Hence all the juming through hoops to get this thing figured out. So have you got the series and shunt terminology backwards or am I about to relearn what I thought I already knew? Thanks, MikeK
I agree, but what he said was (as I read it) I turned my shunt into a series field that would mean the same current that goes through the armature would necessarily go through the (41 ohm) shunt. Hence my answer.
I have since that post got additional info, I now know the motor is a differential compound motor.
Ya, I guess that's just for simplicity of drawing.
The motor has 4 sets of brushes and each set has two brushes (more surface).
Thanks, MikeK
You don't operate the shunt field in series with any counter parts of the Series field or armature..
The field is either operated by a fixed DC source or to the same source as what drives your armature.
I'll make an attempt to graph it. Connected like most are on systems that use compound machines.
Fixed Field supply >>>> (+)---------field------------(-)
Drive Feed(+)>>(S+)--(S-)--(A+)--(A-)>>>(+)-----Field----------(-)
I Agree.
I assume your still discussing the shunt field. There are many sources that discuss adjusting the shunt field current. So it would not always be operated by a fixed DC source. Here's one. "Control is obtained by weakening the shunt-field current of the dc motor to increase speed and to reduce output torque for a given armature current."
Ok
Ah, there we go.
I had to go back and look :-) Ok, I'll take all the blame for my confusion. First I'm using a PWM motor controller, it varies the current through motor. I never thought of that as controlling the series field current, just the current through the armature. Most of that is because for the year I have been using the motor I didn't know it had a series field. I thought I had this;
Ok good to know, although I will never try to run my motor with an open field coil again. The first and last time I did it I blew my motor controller. Maybe coincidence but it shut down with a fault and after clearing the fault we ran it again this time the fault never cleared. Thank you very much for taking your time to help me. MikeK
now you understand :) Yes, you have a motor that looks like is designed for one direction. you connect F1 to the F2 via a R if you want to control the shunt field strength or, just couple them together for full power which makes it a
2 wire motor then. That motor looks like it'll operate on DC/AC,like a universal motorthe other side of the shunt field seems to be tied with the A2 connection. which I find common in systems where the motor is expected to have the A2 tied to a common point and not on an output of a bridged drive.
Have a good..
Actually the other side of the shunt field is tied to the brush and the shunt field current has to go through the armature along with the series field current. As shown here.
From the looks of the stator windings it is compound wound with a compensating winding.
I would have to take the stator apart more to figure it out correctly.
What information is there to had on the manufacturers nameplate?
Judging from the stator photograph, it must be "C" or a variation of it
Since you are not getting to the internal connections you cannot rule that out.
Much clearer. That still does not account for all the brushes. Ples show us how they work out.
Ok, let's reference this into things you might reasonably do:
The stator photograph shows three windings, can you pry out just where they are connected? How are the brushes connected to all this? It may be quite strange. It is really important to have a full connection diagram of all the windings, brushes and well just everything, including polarities (aiding vs opposing in terms of armature current). Please provide the best you can.
There are three stator windings from the insulation colors in the photo. You have stated that thereare 4 brush positions (which matches the stator photo), how is it all connected?
Hi Joseph, Thanks for your input, I don't know what all I've put in this thread, but the bottom line is the motor had overheated wires. At this point I have removed all the windings. My plan is to rewind it as a series motor. It is a four pole motor two were series fields and two were shunt fields. I want to make all four poles series. I will be starting a new thread asking whether inductance is a proper way to figure out the new turns count. Thanks again, Mike.
And the quick answer in normally no. MMF and gap energy vs torque-speed properties. I really recommend compound wound if you can get through the calculations. Say 75% series and 25% shunt MMF average over the speed range. Great bottom end torque without giving up all the top end torque.
------------------------------------------------------------------ This motor appears to be a 2 pole shunt motor with interpoles. Typically a compound motor will have series and shunt fields on the same poles. Interpoles between the normal poles, if used, will have series windings. However interpoles are generally quite narrow (and as I recall, the picture of the field didn't show this) so that they only affect the coils being switched by the commutator in order to eliminate arcing at the brushes under heavy load.
-- Don Kelly cross out to reply
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