Re: [CAD_CAM_EDM_DRO] Unipolar/Bipolar Parallel/Series?!?!?

In a message dated 23-Sep-01 15:05:16 Central Daylight Time,
weyland@... writes:

> On the schematic of my motors, It shows what appear to be four separate
> coils inside, giving you eight wires terminating at screw terminals inside
> the back of the motor.

Not exactly, because you are confusing terms which were PRINTED confusingly
in some (older?) SM catalogs, etc. Think this way: A SM with TWO separate
windings, four wires, is a "bipolar". That just means your power-souce must
have TWO polarities with respect to "ground", i.e., "BIpolar" "Four Phase"
is a quasi-correct way of saying a motor with four windings, whichever way
connected, that is, either as 8-wire, or as six-wire, operates by turning
on/off one or two of the 4 windings. But this is actually only "2 phase",
since the center-tapped ("3-wire windings") are functioning as only ONE
winding each, not two!

So, you have, actually, "Two-phase motors with windings split into four pairs
which may then be connected in maybe three various configurations, to give
you UNIpolar, BIpolar, or CONFUSING."

> Now, when talking of *how* to wire them I come across a few different types
> of terminology: Unipolar and Bipolar, wiring them in Parallel and Series,
> and wiring them in Full Winding and Half Winding. Can someone please
> explain the difference between these for me? Here is what I gather so
> far: Bipolar has only two wires per "phase" or coil. (correct?)

Yes, correct. I have never heard of "full winding" and "half winding". But,
a 6-wire
UNIpolar motor is usually running only at "half-winding", as half of the
winding is not conducting current at any given instant.

"Full winding" must mean ALL the copper is conducting current (one direction
or the other) at any given instant.

Do NOT confuse this with "Half Step" and "Full Step", which is a whole-nuther
topic!

> Unipolar usually has three, but only uses two of them. One of those being a
>

Three LEAD-WIRES per winding? Yes. The "center-tap" is "common" and only
one of the other two (the two "ends" of the winding) is "used" at any
instant, but BOTH are "used" to make the motor run; just alternately!

> To wire my motors in Parallel, I would connect the first wires of two coils
> together and the second wires of two coils together. (correct?) (in my mind
>

Yes. The trick would be to make certain you matched the "start" and "finish"
of each winding, so that the pairs are not wired in "anti-parallel" (think of
winding wire on a nail; you wrap the wire "over the top, and toward you", and
on, around. Now, wind more, only "over the top, AWAY from you". This second
winding would be the "other direction", so would "cancel" the effect of the
first one. Wiring those in parallel would result in twice as much current to
do NOTHING. If both were wound the SAME direction, the "electromagnetism"
would be DOUBLE that of just either one, for this same double current-draw.)

> To wire my motors in Series, I would connect the second wire of on coil to
> the first wire of the next, and use the remaing two for input. (correct?)
>

You have it! And that "tie point" is the "center-tap". Or, if you consider
ONLY the "ends" of the now-double-as-long windings, then you have a four-wire
motor with TWICE the resistance per coil, but FOUR times the inductance, so,
NOT good for high-torque! AND, you'd need special semiconductors (or at
least twice the voltage-ratings!), though only HALF the current, for the same
slow-speed torque. But you wouldn't get the "stepping rate" you could get if
wired in parallel. OR, if you use the center-taps as +common, then you can
"ground" ("sink current") the ends, one at the time, of each tapped winding,
meaning half the copper is idle at any given instant, so, less torque than
possible with bipolar.

> What is Full Winding and Half Winding? Is this an esoteric way of saying
> >

It may be. I never heard this terminology, but I think I touched on this,
above. See "full winding" and "half winding" above. I do not think it is
thought of as (esoteric way of saying) "unipolar" or "bipolar", but, who
knows! I am not very religious.

I began fiddling with "stepper-motor controlled machines" in '79,
center-tapped motors, with home-brew drivers, using a wunnerful "all-in-one"
stepper-motor chip by Sigma, now a collectors' item. Oh, it "drove" TIP-120
transistors, which "drove" the stepper windings. Make it easy to lay-out and
assemble a PCB. (I do my own art, etc.). Then there was a pause. Then I
had need to "get back to steppers", and "bipolar" had become the new
industry-standard during that time, and I have never looked back! I am even
in the process of swapping-out the old center-tapped, unipolar Size-23 motors
on one of my plotters with the new KML061 "high-torque series" by Superior
Electric (link below) and Mariss' 210 drives. VASTLY better! Just hafta
make time to "Stop using, and DO!"!

Thing is: I have nothing "against" a person who is adult and educated, who
is yet not "into" electronics. But it gives me a kind of "shivers" when I
stop and think that there are "folks out there" who think they have read and
asked enough to "do a simple thing", yet have NO clue which end of a
soldering-iron to hold in the hand, nor what "slag" or "Multicore" mean,
etc.! Nor, how to clean off the end of an "enameled" magnet-wire for
soldering, etc. Nor what "heat-sink compound (grease)" is. Etc. Stuff one
simply must know, second-nature, before expecting successful results from
some home-cobbling! Find some neighbor who "does/did that" to come over and
at least "watch over your shoulder", before contemplating smoking a couple
$hundred in nice, new goodies!

Lotsa luck! Lemme know if you now have more specific questions about said
topic.

Jan Rowland, Old Troll


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