Re: [CAD_CAM_EDM_DRO] Re: Before I make a mistake, what do I need to know?

> As Chris S mentioned, you have some of the venerable IBM printer
> motors: 2_/step, 1.4A (so they could use "modified" 1/2 stepping,
> where the current is increased when a single phase is active.

Nifty idea! Got any clever implementations? I'm trying to think what
would happen if both H bridges shared the same sense resistor - I
think the results might not be good though. It may be better to
switch the chopper reference voltage between two levels.

One also has to ask if the limiting factor is heat dissipation in the
motor as a whole, or heat transfer from the winding to the case. If
it is overall heat dissipation then this works. If it is heat
transfer, I don't like the idea of running the winding above rated
current. (Or were you going to run the windings at rated current only
when only one is on, and reduce for both phases on?). However if one
rewired the motor to an 8 lead configuration and paralleled the coil
halves then it would be okay to use higher currents.

[And speaking of our favorite topic, demagnetizing the rotor, wouldn't
putting say double the rated current through one winding increase the
applied filed in certain orientations near the danger zone?]

Chris



--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT