Compound motor question

[WTRVS]

Hello,

I'm trying to understand something for already a long time but I can't really find the answer. I've been looking in many books and websites but everytime I find diagrams that are very theoretical and for me not understandable

It's about compound motors, I would like to know the difference between the types of compound motors and how it looks like in reality. All I find is theoretical diagrams but with that I don't know how it looks like in real life.

I've found a circuit diagram of a compound motor and I have so many questions about it that I don't know where to start.

Anyway I've included an example in attachement:


- If you connect terminals 1 & 2 to a DC source, the motor will run as a series motor, correct? Will it run in the first place without connecting the field winding?

- If you connect terminals 1 & 3 to a DC source, the motor will run as a compound motor, correct? Is this then a "self-excited" compound motor?"

- Why does this motor have two field windings?

- How does do series and shunt windings look like in real life, does anybody have pictures that show these?

- Where are the field windings located in a compound motor? Anybody have pictures of this so that I can imagine how it looks like?


For most of you these are very basic questions but I would like to find somebody who can explain me this in an easy way("For dummies") and if possible with pictures.


Thanks in advance!

WVS

 

[waross]

What types of motors have you seen?
An AC motor generally has a stator. A DC motor will have two or more poles. The shunt winding and the series winding will be wound on the same poles. There are sometimes small poles called interpoles or commutating poles. These are between the main poles and are series poles. They are often not shown on diagrams. They are permanently connected in series with the armature. The armature leads, A1 and A2 often include interpole series windings.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[WTRVS]

Thanks Waross for your reply.

So the shunt and series windings are wound on the same poles? It it true that the series windings are very thick wires and with very few turns and the shunt have alot of turns but a small diameter?

Where are the field windings located? Does anybody have pictures about this?


Thanks in advance!

 

[waross]

Yes.
On the field poles.

http://ecmweb.com/ops/electric_direct_current_motor/

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[WTRVS]

So I assume this is a "self-excited" motor that is shown on the website, right?

But the diagram that is in attachement of my original post, has a series, a shunt and 2 other field windings. Where are those 2 field windings located then? Is this also located on the poles?

I'm really confused about those 2 different types


Thx

 

[waross]

Self excited applies to generators not motors.

But the diagram that is in attachement of my original post, has a series, a shunt and 2 other field windings. Where are those 2 field windings located then? Is this also located on the poles?

Yes I am confused also. A diagram such as that without more information is not a good learning example.
But, All the windings will probably be on the same poles.
The two windings may be for service in either series or parallel for use on two different voltages.

- If you connect terminals 1 & 2 to a DC source, the motor will run as a series motor, correct? Will it run in the first place without connecting the field winding?

I wouldn't run a compound motor as a series motor without the manufactures assurance that it was suitable for series operation.

If you connect terminals 1 & 3 to a DC source, the motor will run as a compound motor, correct? Is this then a "self-excited" compound motor?"

No it is a long shunt connection. And No it probably won't run at all. If it does run it will barely have enought torque to turn. In some motors, the torque may be so little that increased brush pressure may be enough to prevent it from starting. Others may run poorly.
Now if terminal 1 is connected to terminal 3 and power supplied to 1+3 and to 2 it will be a compound motor.
The motor is probably intended for use with a dedicated controller.

Why does this motor have two field windings?

Probably for 110 V or 220 V operation.
This is Engineering tips, for proffesionals; not basic motor training. Had you signed in as "electrical" you may have been booted by now. We do understand that other disciplines run into electrical problems and try to help as a courtesy.
But for now, look for some basic motor books, do some googling and see what you can find.
A last tip. If you know what an automotive starter looks like that is a good building block. (If not- Google!)
Looking in the end with the rotor and brushes removed you will see the two (or four) poles. The steel case is part of the magnetic circuit and forms the return path for the flux.
The heavy (often flat) series windings are wound on the poles. If this were a shunt motor the shunt windings would be wound on the poles. If a compound motor, both series and shunt windings may be wound on each pole although the motor would work if the series coil was wound on one pole and the shunt winding on the other pole.
If there are four poles, the same applies.
If there are small poles between the main poles those will be the inter-poles described above.
Welcome to Eng-Tips

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[WTRVS]

Waross,

Thank you for your post, this was the answer to my questions.


Kind regards,

WV