Max power supply voltage for Gecko G540

[shaper]

Copied out of another thread:

. . . . . Like Brian I too am using the G540, unlike Brian I'm using a motor that is less than ideal for this driver (MK34HS9801) and am happy to accept the trade off that this pairing will give me (largely as the OM motors are rediculously expensive here and I plan to build a second smaller machine with smaller motors once I've got a bit of experience) however I'd like to run these motors at 50V (max for G540) the thing that comes to mind is that often there is variation between published mains voltage (240V here) and what is actually delivered (+/- 10% comes to mind) the problem I have is that if I size a transformer at 35V to get the 50V, what happens when they are +10%? When you apply the stepdown ratio from primary to secondary and then convert to peak you are over the voltage for the drive, I can step down to 30V and trade off further or am I being overly concerned?

Jed

[bfauska]

I don't have the experience of the other folks who helped me out (obviously since I asked them for help) but I would think that with such swings in your supply voltage maybe you'd be better of with a regulated power supply, I think they are designed to stay more consistent with less reliable input power. The price difference (at least here in the states) was moderate when I was looking into it and the only real drawback was the potential for dust damaging the power supply, which if you put it in your control box would be reduced.

[domino11]

Jed,
In an unregulated power supply, if the mains input rises, so does the output of the supply. The percent rise is the same, 10% rise on input, 10% rise on output. I dont think I would want to run a G540 much more than the rated 50V. Mariss, the designer of the G540 had this to say on the geckodrive yahoo group

Re: G540 max voltage?

The G540 is rated at 50VDC, it is designed for and tested at 60VDC
and it comes apart at 68 to 70VDC.

I don't encourage anyone to run it much above 50VDC because that 18 to 20VDC is
a safety margin. A derivation of Murphy's Law yields "If it can happen, it will
happen." Take these 3 "can happen" events:

1) Line voltage goes to the +10% tolerance. 50VDC becomes 55VDC.

2) Rapidly decelerate all 4 axis simultaneously from a high speed to zero. The
supply voltage bumps up 10% for 1/8th of a second.

3) A large AC load dump (compressor, air-conitioner, etc.) occurs. The voltage
surge brightens the shop lights for 1/2 second. The supply voltage bumps up
another 10%.

Now take the "will happen" part and make (1), (2) and (3) simultaneous; add them
up. I get 55V, + 5.5V and +5.5V for a total of 66VDC on the G540. It shrugs it
off like it never even happened.

Run the G540 at 60VDC and you get 66V, +6.6V and 6.6V. I get 69.2VDC and
probably a very dead G540 afterward.

The odds of (1), (2) and (3) happening simultaneously are fairly long, but given
enough time, it will happen. Weeks? Months? As Dirty Harry said "Do you feel
lucky?" :-)

Mariss

the original post Here (http://finance.groups.yahoo.com/group/geckodrive/message/19089)

[shaper]

Heath

Thanks for the Post from Mariss, I don't know how Gerald (and the rest of you for that matter) does it as I have trouble keeping up with this forum let alone, the gecko group, cnczone and no doubt several others. In any case I'm not proposing to run the G540 over the 50V rather at it, was just concerned about the variation in supply voltage resulting in it being run over the 50V and what the result would be, Mariss's post answers this thanks I'll check my numbers and see how they compare to those included in your post.

Thanks

[Gerald D]

Based on the "The G540 is rated at 50VDC, it is designed for and tested at 60VDC
and it comes apart at 68 to 70VDC." I would check my average local mains voltage and pick an unregulated supply that gives 50VDC at that average mains voltage.

If your mains does go high by 20%, you are at the 60VDC design point - an unlikely (in Australia) and safe event. The G540 will come apart when your mains goes 40% over the norm - imagine what else in your country will make smoke if the mains goes over 300VAC? Your little G540 will be the least of your (and your insurance company's) concerns if that happens! :)

[Gerald D]

PS. I don't subscribe to the:

"2) Rapidly decelerate all 4 axis simultaneously from a high speed to zero. The
supply voltage bumps up 10% for 1/8th of a second.

3) A large AC load dump (compressor, air-conitioner, etc.) occurs. The voltage
surge brightens the shop lights for 1/2 second. The supply voltage bumps up
another 10%."

factors.

2.) Have measured the rise in voltage when the gantry decelerates and found nothing sigificant.

3.) Voltage surges on load dumps are typical for people running off small generators where the diesel/gas engine has to slow down. We are connected to a massive grid of generators and we just don't see voltage surges as envisaged there.

[Gerald D]

The above discussion deserves a thread of its own