Stepconf question from a newbie!

I am sorry but I know almost nothing, maybe less than that, about Linux, Stepconf, g-code..

However I have managed to install a power supply, break out board, three 2 pole steppers and one 3 phase stepper with 3DM683 Leadshine three phase stepper driver. I have not ventured further than Stepconf while I try to learn how all these pieces work together.

The three 2 pole steppers work as expected but I am having problems with the 3 phase stepper.

The 3 phase stepper is a re-purposed washing machine motor, it has 42 poles on the stator and permanent magnets on the rotor. This motor operates just like one would expect a stepper to work, it steps forwards, backwards and runs fast, I can get a slow step that is barely perceptible watching the motor or it can run at several hundred RPM. Torque is massive!

Now the question for which I would like assistance please. The 3 phase stepper is set up as a rotative axis and I want to test that I have the necessary conversion from 42 to 200 poles correct, I would like to have Stepconf turn the stepper exactly one revolution (i.e. 360 degrees). 360 degrees with this motor is only 42 steps, how can I define that in Stepconf please?

Thanks
John

Click here for an image of the motor...
www.thebackshed.com/windmill/images/FPDiss/FPDiss2.jpg

P.S. I should mention that I tried using the Test Axis window set to 360 degrees but the motor always moves less than expected.

Hi,

The first thing is you probably need to use a type 3 or 4 stepgen, stepconf will not set that for you.

www.linuxcnc.org/docs/html/man/man9/stepgen.9.html

The subject has just been discussed on the users list
sourceforge.net/mailarchive/forum.php?forum_name=emc-users

Don't know if it got to a useful conclusion, the topics seem to quickly go off at tangents sometimes but worth checking.

Search for '3 phase washing machine' or similar

regards

Hi ArcEye, thanks for the reply.

I could not see any real discussion on that users list but I am not familiar with that environment. That, I believe, is possibly an LG washer motor but mine is much older being a NZ made Fisher and Paykel motor but visually very similar.

I dont understand why stepgen would be necessary, I thought the Leadshine 3DM683 did all the step generation. It has inputs for pulse, direction and enable and outputs for the connections to the star or delta connections of a 3 phase stepper. Where I am at the moment Stepconf can drive the F@P motor fast or slow, steps forward or back. I can leave it for several minutes stepping back and forth in the Test Axis window and it will reliably return to start point.

It will be interesting to see if anything comes to pass on the users list.

Meanwhile, something I would like to know is does the Test Axis back and forth test use the full defined test area?

John

Ok, now able to look up the driver.

I dont understand why stepgen would be necessary, I thought the Leadshine 3DM683 did all the step generation. It has inputs for pulse, direction and enable and outputs for the connections to the star or delta connections of a 3 phase stepper.

The driver does not generate the steps, but it looks as though it takes normal type 0 stepgen pulses and outputs the required to a 3 phase motor.

This is the thread re the washing machine motor
sourceforge.net/p/emc/mailman/message/33166294/

Don't know if there is anything relevant in there, you already have a means to drive it

The stepconf test is really just to see if your motors move, the only thing that matters is how the machine moves using the config it produces.
If it moves less than the commanded distance, generally the scale figure needs adjusting
It appears you do not have it connected to anything, so whatever scale has been calculated is almost certainly wrong

On the Axis page of stepconf, you need to set the steps per rev, driver microstepping, pulley teeth and leadscrew pitch to values that equate to a 1:1 movement before your motor shaft will move the expected amount.

Whether it is worth the effort, is debatable, as I said it is just a confidence check that the motors move, the settings are meant to relate to the machine being moved.

regards

You are right, probably not worth the effort for someone who has been this way before but this is all new for me and I really need to understand every step along the way if I possibly can.

I realise that one of my errors has been thinking this motor has 42 steps when in reality it has 126 (42 x 3) so that is something to check today.

Brgds
John

The number of steps for this motor is actually 112. I dont understand how it can be that but it is!

If anyone else is trying to use one of these ex washing machine/ air conditioner/ heat pump pancake 3 phase motors as a stepper the number of steps is 8 x number of coils.

Hi Andy

That _isn't_ a stepper motor. It is a three-phase brushless motor. You can run it as a stepper but it will get very hot and won't run anywhere near rated power.
This is a video of me running one that I have with LinuxCNC.

My Fisher and Paykel motor(s) is similar but not identical to the LG and Samsung motors. It is not showing any signs of over heating but I am not driving it at anything like the power levels it carried in washing machine service.

These motors can be heavily modified and one useful modification is to wire the coils in parallel, or at least series/parallel. This will reduce the inductance and allow much quicker current rise and fall.

I spent a bit more time today messing with various configurations of the F@P stator. One stator has been cut down to just 18 coils ( v:42) and I converted that to each phase consisting of six coils in series parallel (3 coils x 2).



This is by far the fastest configuration I have ever tested with a top speed of 600 rpm. I need to think some more and decide if further improvements are possible. Of course speed is not everything and low speed torque is probably more important.