[wesc]

Hi Folks,

I'm in the process of converting my Shoptask Bridgemill to CNC. I'm considering using the following motors

http://cgi.ebay.com/3-640-oz-in-Bipo...QQcmdZViewItem

640OzIn Steppers, 2.3V, 5.5A

using Gecko 210 drives.

My question is, will the following power supply work for me.
http://www.allelectronics.com/cgi-bi..._STATION_.html
($95!)

Is 24V enough? 6+6+21 amps is enough, i think. Acording to the Gecko manuals, you can drive servos at up to 25x the rated voltage or 57V. I see that Dan Mauch specs 36V supplies for similar steppers...

Thanks,
Wes

[CJL5585]

Is 24V enough? 6+6+21 amps is enough, i think. Acording to the Gecko manuals, you can drive servos at up to 25x the rated voltage or 57V. I see that Dan Mauch specs 36V supplies for similar steppers...
-----------------------------------------------------------------------------
Wes,
The power supply would allow your system to operate, but you would be limited to lower feedrates than you could attain with a 36 Vdc or higher voltage.

I agree with Dan that your voltage should be AT LEAST 36 Volts.

I run my system on 48 Volts which causes the motors to heat excessively after 3-4 hours of continious operation, but not many hobby projects take that many hours, so in reality it is not a problem. I am recommending a voltage range of 36 to 48 Volts. That will give you more torque and higher feedrates.

Jerry

[wesc]

Thanks Jerry.

I see that the power supplies are isolated. So, I should be able to parallel the two 6 amp supplies and put them in series with the 24 amp supply. That gives me 48V at 12A max -- not quite the full rated amperage of the 3 steppers combined (16.5A). Do you think that 12A will be enough?

-Wes

[ger21]

Geckos only need 2/3 of the motors rated current, which is about 10A for all 3 motors, so 12amps should be fine.

[CJL5585]

Geckos only need 2/3 of the motors rated current, which is about 10A for all 3 motors, so 12amps should be fine.

Same here.

Jerry

[pminmo]

Hmm... thats 5.5A per phase, or 11A per motor for a 2 phase motor or 33A total for 3 motors at 2/3 would be 22A?

[Oldmanandhistoy]

Hmm... thats 5.5A per phase, or 11A per motor for a 2 phase motor or 33A total for 3 motors at 2/3 would be 22A?

I would like to know the answer to this also. One other thing, if I buy a stepper motor and it does not say how many phases it has, how would I know?

John

[ger21]

Hmm... thats 5.5A per phase, or 11A per motor for a 2 phase motor or 33A total for 3 motors at 2/3 would be 22A?

Here's a quote from the Gecko stepper white paper.

"The choice of a power supply is determined by voltage, current and power supply type, i.e. switcher versus linear regulated versus unregulated and purchased versus in-house designed. By far the most problematic factor is voltage, so we will leave it until last.

The easiest factor in choosing a power supply is its current rating. The current rating of the supply is based on your motor choice. The drive will always draw less than 2/3 of the motor’s rated current when it is parallel (or half-winding) connected and 1/3 of the motor’s rated current when it is series (or full-winding) connected. That is to say, a 6 Amp / phase motor will require a 4 Amp rated supply when parallel connected and a 2 Amp rated supply when series connected. If multiple motors and drives are used, add the current requirements of each to arrive at the total power supply current rating."

[pminmo]

I believe gecko is referring to an 8 wire motor, and how it is rated. The motor spec'd in the original post is a 4 wire motor, rated at 5.5A per phase. The highest current point is roughly 141% of the single phase rating, assuming sine/cosine waves at their highest sum. (45, 135, 225, and 315 degrees) So at those angles if the motor was stopped it would be pulling 7.8A assuming the drive is pushing the motor to the rating. Worst case would be all three motors stopped and the max current angle then would be 7.8A *3 or 23.65A. The least case would be 100% or 5.5A *3 = 16.5A

Admittedly it's late and my brain is half fried at the end of the day, but I think I'm thinking correct. But I could be wrong.

[wesc]

So, there's 2 motors on ebay right now that I'm looking at. Both look the same and have similar specs. One is a 4 wire stepper (these URLs are for completed auctions, but both sellers have relisted the same motors again -- both at the same price too)

http://cgi.ebay.com/ws/eBayISAPI.dll...Pr4_PcY_BIN_IT

the other is an 8 wire model

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

http://www.kelinginc.net/KL34H280-45-8A.pdf

which is specced as a "4 phase" stepper, which i believe really means it's a 2 phase stepper.

It seems to me that the 8 wire model would be better (they are the same price) because it'll give me more options in terms of serial/parallel wiring configurations.

Opinions?

Thanks for all your help in untangling all the confusing and sometimes contradictory information out there on steppers.

[jeffs555]

Admittedly it's late and my brain is half fried at the end of the day, but I think I'm thinking correct. But I could be wrong.

What you are missing is the duty cycle, which would be rather low with a 2.4v motor and a 48v supply. The average current out of the supply with a chopper drive would be much lower than 23.65A even if all the motors were stopped at the max current angle. He would probably need a large capacitor to supply the instantaneous current, but the average current out of the supply would be fairly low.

[ger21]

I believe gecko is referring to an 8 wire motor, and how it is rated. The motor spec'd in the original post is a 4 wire motor, rated at 5.5A per phase. The highest current point is roughly 141% of the single phase rating, assuming sine/cosine waves at their highest sum. (45, 135, 225, and 315 degrees) So at those angles if the motor was stopped it would be pulling 7.8A assuming the drive is pushing the motor to the rating. Worst case would be all three motors stopped and the max current angle then would be 7.8A *3 or 23.65A. The least case would be 100% or 5.5A *3 = 16.5A

Admittedly it's late and my brain is half fried at the end of the day, but I think I'm thinking correct. But I could be wrong.

I don't know enough to explain why I think I'm correct, but I own a Xylotex drive, 3 axis at 2.5a per phase. By your thinking, that means I'd need a 15a power supply. But Jeff, the owner of Xylotex, says that it will never draw more than about 4.5a, and in fact sells complete ready to run kits with 4.5a supplys. This is basically the same formula that Gecko uses.

[pminmo]

Jeffs55,
Yes your correct, I wasn't thinking right, forgot duty cycle. They used to say don't buy a car that was manufactured on a Monday or Friday becuase they were more prone to defects. My brain kind of works that way, only its morning and evening Mon thru Fri. (chair) :frown:

[H500]

Wesc, i think an 8 wire motor is better. There is much more versatility in how to drive them. The only catch is that more wires means more chances to make a mistake that can cause serious damage.

[ViperTX]

So, Jeff has measured this at 100% duty cycle....or is it the case.....'if it don't work, slow it down'........

[CLaNZeR]

Here is an explanation regards ampage required at stated motor voltage.


>1.67amps?
>
>If so, that's not enough, especially with the stepper drivers set at
>3.45v ( = 2.4 amps. Times 3 axis = 7.2 amps total needed for the
>system*)

This is not correct. The switching action of the Xylotex controller plus
the inductance of the stepper motor have a sort of "transformer" effect.
Suppose the power supply is 24 V, but the motors are need 2.4 V at 2 amps
for full torque. If the Xylotex is set to deliver 2 A to the motor, it does
deliver 2 A average. But the power supply only has to deliver 0.2 A at 24
V, or a little more. 0.2 A at 24 V (from the power supply) is the same
amount of electrical energy as 2.0 A at 2.4 V (delivered to the motor), so
there are no energy conservation laws being broken. But the power supply
current is far less than the motor current.

What actually happens is that the Xylotex draws current from the power
supply about 10% of the time, and uses nothing the other 90% of the time.
The peak current from the power supply is in fact about 2.0 A, but because
of the duty cycle the average current is only 0.2 A. Average current
determines the size of power supply needed. But the motor current averages
2.0 A all the time, so the motor develops full torque.

The place where you need more current from the power supply is at higher
motor speeds. As the motor runs faster, the winding current stays constant
(thanks to the Xylotex) but the voltage goes up, which requires more power.
Since the power supply voltage remains constant, the power supply *current*
increases in step with the motor *voltage*. So to run motors fast,
particularly with more than one motor moving at once, you need more current.

1.67 A should be plenty to run one motor at low speed.

posted here:

http://groups.yahoo.com/group/Xylotex/message/2384


Regards

Sean.

[eidos]

hi all

la corrente che scorre in un avvolgimento dello statore di una fase motore é:
1) direttamente proporzionale alla tensione "Volt "
2) inversamente proporzionale alla resistenza di fase in "Ohm"
3) inversamente proporzionale alla impedenza della fase "mHenry"
4) inversamente proporzionale alla frequenza di pilotaggio "step/s"
5 inversamente proporzionale alla freq di PWM o chopper.

dire che un motore con le fasi in parallelo assorbe 2/3 della corrente nominale , o che un motore con le fasi in serie assorbe 1/3 della corrente nominale DC, per cui il motore stepper é costruito , equivale a dire niente....... se non si tiene in considerazione come un avvolgimento reaggisce al fluire della corrente e come si oppone al suo scorrimento.

Oltretutto la corrente indicata dal costruttore , indica soltanto la massima corrente di fase ad una determinata tensione, " V*A " = WATT ! di lavoro max, per cui il motore resta in un range di temperatura accettabile senza danneggiarsi , e non che quelli siano i valori di corrente e tensione ottimali per ottenere le migliori performance da quel motore.

hi all

Totillos
www.cnc-elettronica.it

[vacpress]

oui.

[andy_ck87028]

Hi

If I were to buy a 48Volt 50 amp switch mode rectifier that is intended for use as backup for charging solar panel batteries (240V AC to 48V DC), would that be the correct purchase for 3 680Oz steppers (4.3 amp phase current - 2 phase) (url = http://www.clickautomation.com/produ...d=2387&cid=159) controlled by 3 * Gecko 201s?

This might sound a very intelligent question but I can assure you there is no understanding behind this question apart from persistent deductive reasoning and head scratching

I have the Geckos, I have selected the steppers and I have the option to buy the rectifier but I don't know for sure that it will suit my need.

Hopefully this supplements the existing thread and doesn't cut across it.

Andy