Re: [CAD_CAM_EDM_DRO] 4 phase PM type stepper

cadcamcenter@... wrote:

> Hi,
>
> Hoping for some answers for the hopefully not too irritating
> questions:
>
> MOTOR SPECIFICATIONS:
> No. of phase : 4 phase PM Type (pulse modulation?)
> Step angle : 7.5deg+-5%
> voltage : 5
> winding resis: 70 ohm
> winding induc: 30mH (1Vrms 1kHz)
> start pulse rate: 600pps
> slew pulse rate: 610pps
> holding torque : 180g-cm
> no. of wires : 6
> QUESTIONS:
>
> What is the difference between 2 phase and 4 phase steppers?

Really, there are no 4-phase steppers. The confusion is between
2-phase 'bipolar' and 2-phase 'unipolar' drive schemes. Since the
2-phase 'unipolar' scheme has 4 wires from the motor driven in
various combinations providing 4 different polarities of current,
it is sometimes called 4-phase drive. this is really a 2-phase motor
driven in a scheme in which there are 4 states, with current flowing
in (at least part of) both windings all the time. This is commonly called
unipolar full-step mode. 6 wire and 8 wire motors are most easily
used in unipolar drive, most modern drives use 4, 6 or 8 wire motors
in bipolar drive.

> Are 7.5 deg. steppers good enough for CNC work?

Probably not. Although, with fine-thread leadscrews or reduction
mechanisms the resolution would be acceptable, the high speed
performance, acceleration and vibration of these motors are all
much less desirable than 1.8 degree motors. Unless you will be engraving
lettering on wedding bands, these motors are WAY, WAY too small
for CNC work! the 70 Ohm, 20 mH windings will SEVERELY limit
power and speed to very low levels. 600 steps/sec (from specs above)
comes out to about 13 RPS. With a 20 TPI screw, that is 39 IPM, or
1 M/min. For a very small machine, that might be acceptable. but,
the ability of this motor to drive a machine table is going to be extremely
limited.

>
> What is starting/slewing pulse rate? What significance does it have
> for motor controller?

In CNC, not much. But, it may be an upper speed limit with some particular
drive chip.

> 1g-cm = ??? oz-in (sorry, but someone on the list will be able to do
> this conversion without having to hunt for conversion tables)
> Will the motor be compatible with those CCED motor controllers
> (gecko, camtronics, etc.)

Yes, the motor will be electrically compatible with most drives and
controls, but I don't think the mechanical performance will be much
good!

Jon