From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: 3 wire stepper motors
Date: Thu, 26 Sep 2002 11:38:10 GMT
NNTP-Posting-Date: Thu, 26 Sep 2002 04:38:10 PDT
Ralph Seguin wrote:
> I noticed at a surplus shop some Superior Electric NEMA 34 stepper
> motors, 120V, 0.3A, 50 oz-in, 3 wire.
> What is a 3 wire stepper motor?
> How does one drive them?
> I have a really small budget ($0 if you ask my wife :-), so I don't
> think I can afford all the nice servo and stepper stuff.
> I have a 3 axis stage with 10 TPI Acme screws on X and Y and a
> ballscrew on Z that I'd like to make into a little mini-CNC mill.
> I know that 50 oz-in is pretty low compared to some of the 150-250
> oz-in motors that I've seen, but those other motors are pricey.
> I was thinking of rectifying 120V AC to 120V DC and using that as a
> power source, or maybe rectifying 240V AC to DC. Is this a bad idea?
> Are these motors worth investigating, or should I save my pennies?
> Inexpensive source for kick ass motors, drives, controllers, ...? :-)
> Inexpensive source for power FETs?
> Inexpensive source for rectifiers?
> Inexpensive source for power diodes?
> rpseguin AT yahoo DOT com
These motors are probably intended as synchronous drive motors. They
have a stepper motor structure but they are normally connected to the
power line using a capacitor to phase shift the input to one winding.
They can be used as steppers by using a driver that can drive positive
and negative. The junction of the two windings is then grounded. Whether
these have enough torque or not depends on a lot of factors including
the cutter size and material to be cut. Using Acme screws is a bit
painfull because the gibs have to be pretty tight to avoid chatter. You
probably won't be able to down mill even at that because of screw lash.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org