G251 Max voltage

[Dylwad]

Is it safe to run right at 50 volts unregulated no load on the 251's?
I thought I read somewhere they are 60VDC max, but to use a 50V or lower supply. Cant find that reference now though....

Is current sinking in to the power supply during rapid deceleration a problem at these power levels? Would it be safer to run a 48 volt supply or an external current sink (want to stay away from that!)

Amazing how small the 251's are for their power handling!

Thanks,

Dylan

[skullworks]

I setup a system with 3x G251 running at 3.5A.

Powersupply is the Keling 5010 unit and I measured a 50.6V with all drives active and motors attached. E-stop kills AC power to the Keling and shorts the powersupply thru a 100W lightbulb.

You do get the max performance from the motors/drives but you are on the edge. Having a serious load dump for an E-stop condition is part of your best protection.

I would not power up the G250/G251 without the motor attached and I would want at least 2 drives to share the load. This means you are effectively using the drive & motor as a partial load resistor to cut the open circuit voltage level. Just remember that for this to work the drives must stay in an enabled state. ( I just didn't wire in the disable.)

Another item which can't hurt (added insurance) is to make one each of the back-feed dump circuits using the schematic from the Gecko website and wire them for each drive as described.

A G251 drive with a good stepper running at 50V is a big eye opener if you have only used 'marginal' drives at lower voltages.



Also consider how stable your incoming AC line is, it won't take too much of a surge to put you into the magic smoke region. You must consider risk vrs reward.

Good Luck.

[Dylwad]

Thanks for the Reply,

My only other experience with steppers was 640 Oz running 55 volts at 5 amps off of G201's, I had enough overhead on the drives to not worry about a current dump. That machine has been running for 5 years without a single problem, only had to hit E-stop a few times though, usually just hit the E-stop in the software if trouble arouse during a cut.

The 5010 looks like a nice supply, I was going to put something similiar together, I have a few large caps already, 1 47000uF 80V and 2 18000uF 67volts. Dead high end audio amps and recievers are a great source for filter caps.


Ill be running 3 motors, interesting idea about not using the disable connected to E-stop with the light bulb.


I have a friend in the A/V field, Ill see if he can dig up a line conditioner for me.

What relays are you using to switch from AC power to the bulb?

Gecko's returned energy dump circuit looks easy enough to build, Makes me wonder why they dont manufacture them to compliment their drives. Should cost a few dollars per piece to make in quantity. I also wonder if you could get away with a lower voltage capacitor on the G251's, they call for a 100 volt.

Thanks!

Dylan

Originally Posted by skullworks I setup a system with 3x G251 running at 3.5A. Powersupply is the Keling 5010 unit and I measured a 50.6V with all drives active and motors attached. E-stop kills AC power to the Keling and shorts the powersupply thru a 100W lightbulb. You do get the max performance from the motors/drives but you are on the edge. Having a serious load dump for an E-stop condition is part of your best protection. I would not power up the G250/G251 without the motor attached and I would want at least 2 drives to share the load. This means you are effectively using the drive & motor as a partial load resistor to cut the open circuit voltage level. Just remember that for this to work the drives must stay in an enabled state. ( I just didn't wire in the disable.) Another item which can't hurt (added insurance) is to make one each of the back-feed dump circuits using the schematic from the Gecko website and wire them for each drive as described. A G251 drive with a good stepper running at 50V is a big eye opener if you have only used 'marginal' drives at lower voltages. Also consider how stable your incoming AC line is, it won't take too much of a surge to put you into the magic smoke region. You must consider risk vrs reward. Good Luck.

[H.O]

There's no need to have a returned energy dump circuit for each drive. As long as the drives are connected to the same power supply one such circuit is enough.

/Henrik.

[Dylwad]

Thanks Guys,

Ordered a 34 volt Toroid and the components for the energy dump. The 34 volt transformer whould put me right at 50 volts with no load, 46 at full load.

Also ordered 2.8Mh 3.5A steppers to make the best use of the voltage.

Should be nice and fast with 1/2-10 5 start leadscrews and a 60-70 Lb gantry.

[skullworks]

I'm cheap. A single 10A @ 230V SPDT toggle switch is used as the E-stop.

In the up position the hot leg of the 110VAC line is switched on, it then runs to a SSR which switches power via software/computer control. In the down position the DC side is shorted. There is no "center off" detente position.

Another pair of contacts allows feedback to the control as to E-Stop state. On the other side of the 'H' switches a 12ga. line from the DC out of the power supply to ground through a 100W screw in light bulb socket. (the truly paranoid would use 2 sockets in parallel in case 1 bulb blew)

I have an irrational hate for power supply circuits which use un-switched bleed down resistors. It fails my un-official "Energy-Star" Green rating.... As in It would be wasting my "Green backs" having that wasted power loss. Over the long term it does add up.

[Dylwad]

You should get rid of the SSR's too then Im using mech relays, 5 volt coil 1 amp dpdt signal relays feeding 12 volt coil 25 amp ice cubes for the high power stuff. I burned up too many SSR's switching inductive loads, hopefully these work better, and they were less than half the price of SSR's.

I should be able to use the 5 volt relay to switch the bleed resistor in the off state. Thanks for the idea, I had not thought of it.

I do hope that if an un-switched bleeder rubs you the wrong way that you have everything in your house that can be turned on via a remote plugged in to a power strip that gets shut off when not in use What would be cool is a separate 12 volt input on such devices just for the remote turn on powered by solar....

[Jason Marsha]

Originally Posted by Dylwad Thanks Guys, Ordered a 34 volt Toroid and the components for the energy dump. The 34 volt transformer whould put me right at 50 volts with no load, 46 at full load. Also ordered 2.8Mh 3.5A steppers to make the best use of the voltage. Should be nice and fast with 1/2-10 5 start leadscrews and a 60-70 Lb gantry.

Who did you order the 2.8Mh 3.5A steppers from?

[tumutbound]

Originally Posted by Jason Marsha Who did you order the 2.8Mh 3.5A steppers from?

You can get 387oz-in, 3.5A, 2.8mh steppers from here or Homann Designs

[Dylwad]

I ordered them from Keling http://www.kelinginc.net/NEMA23Motor.html

[Jason Marsha]

Thanks Geoff and Dylwad.



Jason

[Crevice Reamer]

Originally Posted by Dylwad I ordered them from Keling http://www.kelinginc.net/NEMA23Motor.html

The Keling 387s have an inductance of 4.1 mH, so they are 65V motors. To get the best performance G540/251 motor from Keling, get the 381, which IS a 2.8 mH 54V motor.

CR.