Electromagnetic/DC motor gurus...

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H

Howard

Lifer
Oct 14, 1999
47,982
11
81
Originally posted by: FrustratedUser
That was better.
How are you connecting the rotor.
Looks like it aint gonna run like that.
Click to expand...
It's a DC motor with series-wired armature/electromagnet, with a 3-pole commutator. I was just wondering if the resulting magnetic field would run the armature.

If you have a better idea of how to strengthen the electromagnet, or even a better design that uses a 3-pole armature, give it a shot.

Thanks!
 
A

Akira13

Senior member
Feb 21, 2002
708
0
0
You probably wanna take a look at How Stuff Works for more info. I should know this... too busy studying statistics and digital logic...

Edit: I didn't see the armature wiring scheme. Looks good, although I think the poles still have to come in pairs.
 
H

Howard

Lifer
Oct 14, 1999
47,982
11
81
One more question:

Why is the lamination stack here shaped like a pick-axe instead of just being cut-off? Is it to spread out the magnetic flux of the windings?
 
S

syberscott

Senior member
Feb 20, 2003
372
0
0
Originally posted by: Howard
One more question:

Why is the lamination stack here shaped like a pick-axe instead of just being cut-off? Is it to spread out the magnetic flux of the windings?
Click to expand...
Two things that matter for magnetic force are surface area and proximity. The pickaxe design accomplishes both.
(I have a migrain right now, so I hope that made sense).

 
H

Howard

Lifer
Oct 14, 1999
47,982
11
81
Originally posted by: syberscott
Originally posted by: Howard
One more question:

Why is the lamination stack here shaped like a pick-axe instead of just being cut-off? Is it to spread out the magnetic flux of the windings?
Click to expand...
Two things that matter for magnetic force are surface area and proximity. The pickaxe design accomplishes both.
(I have a migrain right now, so I hope that made sense).
Click to expand...
Thanks!
 
Analog

Analog

Lifer
Jan 7, 2002
12,755
3
0
it should work, but I don't understand the horseshoe. Why not just wire two separate electromagnets, one on each end?
 
H

Howard

Lifer
Oct 14, 1999
47,982
11
81
Originally posted by: yellowfiero
it should work, but I don't understand the horseshoe. Why not just wire two separate electromagnets, one on each end?
Click to expand...
Less reluctance.

BTW, would using a square-section electromagnet core affect the strength of the flux between the widening plate things?
 
N

NorthRiver

Golden Member
May 6, 2002
1,457
0
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I am no Guru, but it looks wrong. Don't you think that it being shapped like a horseshoe, it would tend to want to pull the rotor into it. Just a thought, I don't know anything about this?
 
H

Howard

Lifer
Oct 14, 1999
47,982
11
81
Originally posted by: NorthRiver
I am no Guru, but it looks wrong. Don't you think that it being shapped like a horseshoe, it would tend to want to pull the rotor into it. Just a thought, I don't know anything about this?
Click to expand...
Most of the lines of force emanate from the poles, but even if that were the case, the only thing that would happen would be an increase of friction between the axle and its sleeve.
 
K

KMurphy

Golden Member
May 16, 2000
1,014
0
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It won't work like the simple schematic you posted illustrates. You have to excite the field in the armature with an external voltage source. You must have pole pairs - there is no such thing in the universe as a mono-pole magnet.

The commutator is used to reverse the polarity of the excitation field to repel/attract the poles of a natural, rare-earth or electromagnet; causing rotation. To change the rpm of the armature, you must change the resistance in the windings. The way your schematic is drawn, the armature would turn zero rpm. How big of a device are you trying to make and what is the driven load?

The wedge shaped lamination stack is also used to secure the windings when the armature is turning.

Go here for more info that is pretty easy to understand.

http://www.tpub.com/neets/book5/16g.htm
 
E

Eli

Super Moderator | Elite Member
Oct 9, 1999
50,419
8
81
Originally posted by: KMurphy
It won't work like the simple schematic you posted illustrates. You have to excite the field in the armature with an external voltage source. You must have pole pairs - there is no such thing in the universe as a mono-pole magnet.

The commutator is used to reverse the polarity of the excitation field to repel/attract the poles of a natural, rare-earth or electromagnet; causing rotation. To change the rpm of the armature, you must change the resistance in the windings. The way your schematic is drawn, the armature would turn zero rpm. How big of a device are you trying to make and what is the driven load?

The wedge shaped lamination stack is also used to secure the windings when the armature is turning.

Go here for more info that is pretty easy to understand.

http://www.tpub.com/neets/book5/16g.htm
Click to expand...

Perhaps we're looking at different images? I don't see anything in his illustration that would prevent it from working.

It is very easy to make a dual-pole armature out of a paperclip. You can even use paperclips for the axle supports.

You can then use any other magnet you want to drive the motor.. Can make your own electromagnet, or use a speaker magnet, whatever.
 
H

Howard

Lifer
Oct 14, 1999
47,982
11
81
Originally posted by: KMurphy
It won't work like the simple schematic you posted illustrates. You have to excite the field in the armature with an external voltage source. You must have pole pairs - there is no such thing in the universe as a mono-pole magnet.

The commutator is used to reverse the polarity of the excitation field to repel/attract the poles of a natural, rare-earth or electromagnet; causing rotation. To change the rpm of the armature, you must change the resistance in the windings. The way your schematic is drawn, the armature would turn zero rpm. How big of a device are you trying to make and what is the driven load?

The wedge shaped lamination stack is also used to secure the windings when the armature is turning.

Go here for more info that is pretty easy to understand.

http://www.tpub.com/neets/book5/16g.htm
Click to expand...
Nobody said that was a monopole magnet? There's an N and an S. I also know the function of a commutator. I noted in the topic post that the commutator design and the wiring setup is done correctly.

The armature may be 3-4" in diameter.

EDIT: The armature will be driving no load except overcoming its inertia during spin-up and friction. The objective is to create a motor that spins at the fastest speed.
 
E

Eli

Super Moderator | Elite Member
Oct 9, 1999
50,419
8
81
Is this for a school project, or just for fun, or what?

Will the RPM of the motor actually be measured and compared with others, to see who's is the fastest?
 
E

Eli

Super Moderator | Elite Member
Oct 9, 1999
50,419
8
81
Originally posted by: Howard
School project. We'll be using retinal dynos to measure the RPM.

:)
Click to expand...
Bah! How ghey. :p

At least invest in a vibration tachometer so you can take accurate measurments. :p

How much voltage will you be working with? :D

Do you have to make your own armature and electromagnet from scratch?
 
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