[NIC 77]

Hi there,

I am building a new CNC machine. I am re-purposing parts from another build. I have 4 G201X drivers from Gecko. I have 3 960 oz-in Nema 34 stepper motors from cncrouterparts. The G201X run on a 48V power supply.

I'm very happy with the performance of the G201X on my previous build, I must say that. Premium product for sure.

My plan is to purchase an additional G201x (for a fourth axis) and an additional two Nema 34 steppers (My old build had a Nema 23 for the Z, this one will have a Nema 34). I haven't decided on if I will buy more motors from cncrouterparts or not. I may try something different for the 4th axis, like a Gecko servo drive, and a servo motor as my 4th axis planetary has a gear ratio of 38.5:1, and I may look for a slightly bigger motor for my Z axis that will be pushing two gas springs that help with the weight of the heavy Z.

My question is about motor sizing with the G201X. It has a max of 7A output? So when I look at available motors, how does this equate to Peak amps and Amps / Phase. I will be using 4 wires to connect the steppers.

Some quotes that have me confused:

https://www.geckodrive.com/support/s...ly-basics.html

"The easiest factor in choosing a power supply is its current rating, which is based on your motor ratings. A motor control 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 per phase motor will require a 4 amp power supply when wired in parallel and a 2 amp power supply when wired in series. If multiple motors and drives are used, add the current requirements of each to arrive at the total power supply current rating."

https://www.linengineering.com/resou...-vs-amps-peak/

"Amps/Phase * 1.41 = Amps Peak current. Regardless of whether you remember the reason behind the 1.41 value, it’s crucial to understand this relationship because in most manufacturers, drivers only care about what peak value it can output. And step motors only care about listing the Amps/Phase value. As long as you understand what the difference is, you will be able to talk in the same language to both driver manufacturers and step motor manufacturers."

So according to linengineering, if I have a motor with 6 amps/phase, I need a driver capable of 6 x 1.41 = 8.46 Amps, but according to gecko, I need a driver capable of only 4 Amps?

Which is correct? Also, can I damage my G201x if I use a motor with too high of an amps/phase rating?

Thanks for your help!

[ger21]

What most people do, is set the drive current to match the motors rated current.
But based on that info from Lin, you can actually set your drive current to 1.4x the rated current. This assumes that the chinese motors your buying are rated the same way as Lin's motors. Setting the current too high can damage the motors.

So according to linengineering, if I have a motor with 6 amps/phase, I need a driver capable of 6 x 1.41 = 8.46 Amps, but according to gecko, I need a driver capable of only 4 Amps?

No. According to Gecko, you only need a 4 amp power supply, when the drive is set to 6 amps.

As I said, just about everyone sets the drive current to match the motor, or slightly less, Since most motors will have a max current of 6-7 amps, the G201X will work fine with them.

[NIC 77]

I am all confused. LOL.

The peak current = Amps/Phase*1.41 according to Lin. So a motor that lists a peak current of 6 amps would need a 6 amp driver but a motor that lists an amps / Phase of 6 amps would need a driver of 6x1.41=8.46 Amps.

So rated current = peak current OR rated current = Amps / Phase? I'm not sure what you mean by that. The motors I'm looking at only give an Amps / Phase number, not a rated current or peak current number. This is ultimately the source of my confusion.

I don't understand how you only need a 4 amp supply when the driver is set to 6 amps? Oh wait, does it have something to do with the fact that the output signal is pulsed at 6A while the input is steady at 4A? Is that it? That would explain the discrepancy in the two statements. They're not really talking about the same things?

If what you're saying is, don't worry about it, if you see a motor that is 6 amps/phase, the G201X will be fine with it, at the end of the day, that's probably all I need to know.

I just don't want to make a bad match and pay for it later. I'm also wondering if I'm under-powering the motor a bit if I do that. For example, 5Amps / Phase x 1.41 = 7.05 Amps peak current. So, it's really a waste to buy a motor with an Amps / Phase over 5 amps to use with a Gecko 201x? Not sure if they even make 5Amps/Phase motors. The ones I've seen are 6A/P or 3.5 A/P.

Thanks for your input!

[asuratman]

As I said, just about everyone sets the drive current to match the motor, or slightly less, Since most motors will have a max current of 6-7 amps, the G201X will work fine with them.

Do you think voltage on driver (or PSU) not affecting voltage motor ? For example driver need 48 V and motor 60 volt (due to 6.4 mH inductance on motor)

[ger21]

Rated current = amps/phase. Just set the drive to the amps/phase.

I don't understand how you only need a 4 amp supply when the driver is set to 6 amps?

You quoted Gecko's explanation above. I can't explain it any better than they do.


As I said before, EVERYONE sets their drive current to the amps/phase. You could always call Gecko and ask them what they recommend. As I said before, setting the current too high can damage the motor. So it's safer to just set it to the amps/phase current.

Also, can I damage my G201x if I use a motor with too high of an amps/phase rating?

No.

And, fwiw, I have some 5 amp motors.