How to make a series-wound motor reversible?

Thread Starter

ipsolutions

Joined Mar 24, 2024
6
Hi-
I have a series-wound anchor windlass, which appears to only rotate one direction despite the polarity of the applied voltage. I have taken it apart and can see the armature and field windings. The armature receives the voltage across the brushes (2 in parallel) and delivers it to the field coils with a second set of brushes (there are also two in parallel). There are only two external electrodes, one at upstream input to armature and the other to the downstream side of the field coils.

Here's my question: Is there a way to alter the internal connections to make this motor reversible?

This is pretty old (1986) motor manufactured by Muir in the UK.
 

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Thread Starter

ipsolutions

Joined Mar 24, 2024
6
You just have to reverse the field winding connections wrt the armature..
Thanks for your reply. So it seems i will need two circuits, one for armature and one for field coils. There are two pre-existing terminals on the motor, "A" and "B". "A" provides the power to the armature and "B" provide the other end to the field coils. They are presently wired as in the "OLD" sketch below.

So I will need to drill two holes into the case, and install (1) a terminal connected to the field winding and (2) another terminal connected to the downstream of the armature (ie the brushes). In this way, the two circuits (armature and field) can be powered independently. One motor direction has the same polarity applied to both armature and field coil, and reverse direction with same polarity across armature but reverse polarity across field coils. This is the "NEW" of the sketch below.

This seems simple in concept, but not so simple when I look at the hardware. I want to make sure I understand before I start seriously messing with this thing.
1711306456958.png
 

Thread Starter

ipsolutions

Joined Mar 24, 2024
6
No.
You just need to switch one of the two (whichever is easier) so the polarity is reversed from one to the other, which can be done with one DPDT switch.
But as it is wired, both are tied together, and I can't change one independently of the other. So I still need at least another terminal to access the field coils, don't I?
 

Thread Starter

ipsolutions

Joined Mar 24, 2024
6
Is it also possible or easier to reverse the armature leads instead? A & 2.
If I reverse the armature instead, I still need access to the brushes for rewiring and disconnecting the series connection with the field coils, which takes place at the brushes. I don't see how to do that without cutting the existing connection (See "OLD" drawing).

I love the idea of rotating the field coils 180 degrees, but don't see how to do that conveniently and frequently.

So rather than take up a lot of your time with back-and-forth, could someone look over this sketch and see if I have it right ("NEW")? If my understanding it correct, I'll consider this. But if anyone has a simpler way, I'd love to hear it!

Thanks a lot for your help!

Is it also possible or easier to reverse the armature leads instead? A & 2.
Is it also possible or easier to reverse the armature leads instead? A & 2.
 

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MaxHeadRoom

Joined Jul 18, 2013
28,761
It appears that motor configuration makes it a little harder than normal to reverse! :confused:
Bottom line is one or the other, field - armature (current) has to be reversed WRT the other.
 

LowQCab

Joined Nov 6, 2012
4,199
Are You sure that You don't have a "Uni-Directional" Gear-Box ?,
which will always rotate in a single direction regardless of the Motor's rotating direction ?
.
.
.
 

Thread Starter

ipsolutions

Joined Mar 24, 2024
6
Are You sure that You don't have a "Uni-Directional" Gear-Box ?,
which will always rotate in a single direction regardless of the Motor's rotating direction ?
.
.
.
Yes, I believe the motor itself, just the shaft, only goes one direction regardless of the polarity of the applied voltage.
 

LowQCab

Joined Nov 6, 2012
4,199
That's what I thought the first time I saw one.

There are Gearboxes in which the Output-Shaft always rotates in the same direction,
regardless of the direction of rotation of the Input-Shaft.
I guess that's why I still remember it, it blew my mind as a kid.

Don't ask me what or why, but I held the thing in my hands, and it really does work.
It weighed around ~10-pounds with a Grey-Painted-Cast-Iron-Housing.
This was Military-Surplus, back around ~1965-ish.
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.
.
 

Tonyr1084

Joined Sep 24, 2015
7,954
Screenshot 2024-03-26 at 8.25.09 AM.png
Irrespective of which is actually forward and which is reverse, this configuration will run the motor in one direction. All you need to do is come up with a switching method to reverse the field windings in order to reverse the direction of rotation. Should be easy enough using a DPDT switch as someone already mentioned.
 
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Tonyr1084

Joined Sep 24, 2015
7,954
What the heck is a "Uni-directional" Gear-Box?
That's what I thought the first time I saw one.

There are Gearboxes in which the Output-Shaft always rotates in the same direction,
regardless of the direction of rotation of the Input-Shaft.
TO ME - this looks like a simple worm drive gear box. It doesn't look like a uni-directional gear box. I, too, have seen UD gear boxes. If I'm right there's an idler wheel on a clutch. When you rotate the input shaft in one direction the idler wheel engages. When rotated in the opposite direction a double set of idler gears engage, thus always maintaining the same rotation of the output shaft. My lawn sprinklers have a similar but opposite gear function built into them. The water turbine always spins in one direction but a spring loaded cam latch switches between the single idler or the double idler and will reverse the direction of the nozzle back and forth every time it hits the stopper switch. It's like taking a UD gear box and using its output as an input. To switch the direction of the (what once was) input shaft you'd switch between the idler sets.
 

Tonyr1084

Joined Sep 24, 2015
7,954
This is similar to how the sprinkler reverses direction. In the video the outer ring gear is always rotating in one direction but the inner green (with yellow flag) gear changes direction. Exactly opposite of a UD gb.
 

Tonyr1084

Joined Sep 24, 2015
7,954
Looks like Lego's have a UDgb as well. Pay attention to the worm gear. Notice how it changes position when its rotation changes direction.
 

MisterBill2

Joined Jan 23, 2018
18,964
If the DC motor is a wound-field motor then it will rotate in the same direction regardless of the applied polarity. I own several electric drill motors like that. To reverse a brushed rotor motor the polarity of the field frlative to the armature must be reversed. That is simple with a permanent magnet motor, but requires separate connections to the firld for a brushed motor. That reality has been understood for at least 100 years!!!!!
 
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