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Author Topic: Stepper motor power supply  (Read 8570 times)

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Re: Stepper motor power supply
« Reply #10 on: April 29, 2008, 07:18:00 PM »
Thanks to all with replies,you guys are great
Kristen heres the web site with the drive, sorry took so long for reply
Thanks for bi polar chopper drive info,
The motors i am running are 8 wire so i was looking ahead for next drive.
I think i can run the in bipolar and be 450oz
Anyway thanks for bearing with me!

Offline jimpinder

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Re: Stepper motor power supply
« Reply #11 on: April 30, 2008, 03:47:55 AM »
I just had a look at that site - the drives you are looking at seem to be 3 amp spec.

I  also started with 8 wires motors - rated at 2.5amp @7.5 volts and thus bought some 2.5 amp drives.

8 wire motors have two pairs of two windings, and can be wired together in series, or parrallel - or just using a single winding

I wired mine in series. Without going into a lot of maths which we did in the last post (see "how do I wire my steppers") - if you wire the motors in series you use roughly 1/2 the rated current.

If you wire up using just one of the two windings on each side - you use the rated current.

If you wire up in parrallel - I think we decided you use 1.666 x rated current.

The big thing about it is the power from the motors. I was satisfied in series (my first go) I was pleased to have everything work - but could not get the axis speeds up above 4 ins per minute (48,000 pulses per inch) no matter what I did.
I decided to wire them in parrallel - and the difference was amazing - I could get up to 10 times the speed. Even using a single winding, I was up to 5 times the speed.

The problem was - of course - that having done all this - my drives were not powerful enough to sustain about 4 amps continuously - and I have now moved on to Gecko drives - which are rated up to 7amp at about 80 volts.

CHECK THE RATING  of your motors and find out wether the quoted current is through one winding or two. If you measure the resistance of a single winding and check it against the spec that will tell you - E = IR  - mine were 3 ohms resistance - which gave me 7.5 = 2.5 x 3 which told me that the quoted rating was for only ONE winding in the motor and there were two.

The drives you are looking at seem relatively expensive - so I think you should be able to perhaps invest in some more powerful ones which will staisfy your needs for quite some time.

Drives cards can be limited in current, so buying too big is not a problem.

Sorry is you have already worked this out.

Not me driving the engine - I'm better looking.

Offline stirling

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Re: Stepper motor power supply
« Reply #12 on: April 30, 2008, 08:11:54 AM »
Just read through this thread again and I'd like to ask some (rhetorical) questions.

1) what is "root2" and how does it relate to the rectified/smoothed DC voltage of AC?
2) For an LR driver - what is the max current the PS will need to supply for 3x2Amp motors?
3) If a stepper motor is standing still (holding) what current is it "drawing"?
4) How many rated currents do 8 wire motors have?
5) what is "root2" and how does it relate to single, series and parallel wiring schemes?
6) Why can 2.5Amp chopper drives NEVER source 4Amps - EVER?