Help with non-standard pac-sci stepper

[Argofanatic]

Hello everyone, this is my first post to the forum. I've been reading stuff for months here, and now my parts are trickling in for my first router project.

I lucked out (I think) and purchased 4 new pac-sci steppers on ebay.
They are model #K31SSFS-LEK-SS-02 (non-standard)
From the pac-sci website these are Powerpac Sigmax 1 stack NEMA34 with 845 oz-in holding torque.

On the motor the following information is labeled.
Bi-Polar serial
Is = 5.5A
Vs = 35V
Po = 119W

They are 8 wire steppers.

Since I can't cross-ref the phase inductance or resistance, can anyone help me determine what I should use for voltage to drive these puppies ?

Thanks,
Marc.

[pastera]

Extraplolating from the standard motor - may be way off so measure the phase resistance to see if the numbers are close

series

Rs = 4.3/5.5 * 0.72 = 0.56 ohms
Ls = 4.3/5.5 * 4.7 = 3.7mH
Vs = Is * Rs = 3.1V

parallel
Rp = Rs/2 = 0.28 ohms
Lp = Ls/4 = 0.93 mH
Vp = Vs/2 = 1.55V

The 35v is the max supply voltage with a chopper type drive.

If the actual voltage in series connection is 35v that means the phase resistance would be ~6.4 ohms with an inductance to match (bad).

Aaron

[Argofanatic]

WOW !
That was fast.

Thanks Aaron, I'll break out my multimeter tonight.

[Argofanatic]

Ok, so my trusty multimeter has revealed that I have roughly .4 ohms per phase.
I say roughly because the lowest scale is 20ohms on the meter.

This would give me around 2.2v per phase (5.5 x .4)

Since the motor has a rated Vs = 35V
Does this mean that my PSU should be 35V max giving me a drive of 35/2.2= 16x
?

The motor is also rated for 1500 RPM.

Thanks,
Marc.

[pastera]

Pac-Sci shows a "k" series motor driven with a 75v drive but that seems to be excessive for your 2.2v motor.
Are you going to run these in series or parallel?

Most hobby level drives will not power these motors at full torque in parallel (~540oz-in @ 7 amps) but the you might get better performance anyway because of reduced inductance.

For the 0.4 ohms per phase, did you measure that in series, parallel or just one coil? Also, did you zero out lead resistance when you made the measurement?

The most accurate way with a multimeter would be to put all of the coils in series and measure and divide by four to get the coil resistance. The phase resistance would be half for parallel and double for series.

If you can get two meters, you can set a current through the coil and measure the voltage across it to get a more accurate measurement. This can also be done with one meter if you have a low value 1% resistor to use as a current sense.

Aaron

[Argofanatic]

Hi Aaron,

I simply measured one coil at at time, didn't zero out the leads (I wouldn't know how to do that anyways) I didn't think it was that important.

From the pac-sci documentation however I see 820 oz-in (unless I'm missing something) http://www.pacsci.com/support/docume...er/stepsel.pdf
5.5A with 0.4 ohms

As far as parallel vs series is concerned, I'm at a loss. The steppers say Bipolar series on the label, so must I assume that the specs are for a series connection ?

I'm still looking for some help this, so every little bit helps.

Thanks,
Marc.

[fyffe555]

Ok, couple of things first. PacSci, unlike most manufacturers rate thier motors voltage at the maximum supplied, not the coil rated. In other words a 2.2v coil from one manufacturer would be rated 35v max to the driver by PacSci. You should not exceed 35v to the drivers power supply and set the driver to the motors rated amps..

Similarly you say the 5.5A rating is for Bipolar series, that is the motor is rated for a maximum of 5.5a when wired in bipolar series. The same motor will / should then be rated around twice that for bipolar parallel.... these are serious motors.

So, you have an eight wire motor and until you wire it, it's neither parallel or series. Have a look at the pacsci installation bulletin, http://www.pacsci.com/support/docume...llbulletin.pdf it shows the wiring for series or parallel and gives the colour or pin number connections. You'll probaby have to choose the wiring plan by what the driver can supply.

Andrew

[Argofanatic]

Hi Andrew,

Not exceeding the 35v is what I suspected also, from what I read about the pac-sci motors, that's the way they rate their motors, no mumbo-jumbo.

I'm probably gonna drive these with Gecko 203V's and a G-REX (unless someone advises otherwise).
So I still don't know if I need to to parallel or serial. Top speed if going to be 1500 for two reasons. 1. The motor states 1500 rpm and the THK KR4610D's I'm gonna drive also have a top speed of 1500 rpm. Full out this would give me 590IPM (uh huh). So I guess torque is really where the money is at.

With regards to a power supply am I looking at 35VDC with at least 5.5A or do I need to multiply the current required by the number of motors I have (3) ?

Thanks to everyone for helping me out.
It's greatly appreciated.

Marc.

[pastera]

To zero out the leads, short the two leads and press the "delta" or difference button (or just subtract the value from your readings).

Run the motors in series at 5.5amps with a 35v supply on the geckos. You won't find a cheaper option that will allow you to get full torque wired parallel. It also seems you don't need the speed, so you won't really loose anything wired in series.

Aaron

[Argofanatic]

Thanks guys, I appreciate the help.

I'll be snapping lots of pictures and documenting my build for everyone to enjoy.
Marc.

[slowbob]

Marc,

If your still following this thread, did you ever get these steppers running? I picked up 4 of the same steppers. Also, did you end up getting the geckos?

Any feedback would be appreciated.

I sent you a PM incase your not watching this thread in hopes you would see either this post or the message.

Thanks,
Bob

[Argofanatic]

Yup, got them working.
Sent you a PM also.