[Crevice Reamer]

It seems like all of the available motors either require more volts than 50 or more amps than 3.5. I have found NO Nema 34 motors that run at or below 3.5 Amps. I know I can operate the motors on less voltage, but can I use these drives with a motor that requires more amps than 3.5? Other Geckos that I have known, simply leave off the Current set resistor for their max amp setting, so they can't use motors with more amps than 7.

I mean is there a way to limit these cheap drives to 3.5 Amps even though the motor might want 4.2 or 6.3 Amps?

CR.

[ger21]

It seems like all of the available motors either require more volts than 50 or more amps than 3.5. I have found NO Nema 34 motors that run at or below 3.5 Amps. I know I can operate the motors on less voltage, but can I use these drives with a motor that requires more amps than 3.5? Other Geckos that I have known, simply leave off the Current set resistor for their max amp setting, so they can't use motors with more amps than 7.

I mean is there a way to limit these cheap drives to 3.5 Amps even though the motor might want 4.2 or 6.3 Amps?

CR.

Yes, You'll be able to set the current to 3.5amps. Torque is proportional to current, so a 7 amp motor running at 3.5amps will have half the torque. A 4.2 amp motor will have ~77% of it's rated torque.

If you don't need high speeds, you can get 400 oz Nema 34's that are about 3 amps wired bipolar serial. http://www.kelinginc.net/KL34H260-42-8A.pdf

Bottom line is if you want to spin Nema 34's fast, you'll need full size Geckos.

[Crevice Reamer]

Thanks Gerry! But I think you are missing my point:

The full size Geckos cannot run motors that will draw more than 7 amps. Their setting for 7 amps is NO limit resistor, so there is no protection for a motor of greater than 7 amps.

Apparently, using a motor rated for MORE than the max Gecko amps (7) will harm even the 203V.

So my question concerns the G250/251/G540: CAN I use a motor rated for more than 3.5 amps? (And will the drive limit the current to only 3.5A?) Or, like the larger Geckos, will this cook the drive?

I'm hoping Mariss or Marcus will answer this.

CR.

[LeeWay]

If I recall, you install a resistor directly related to the ammount of amps you wish to draw. 2 amps add a 20K resistor. 3.5 amps, add a 35K resistor etc.

[Crevice Reamer]

If I recall, you install a resistor directly related to the ammount of amps you wish to draw. 2 amps add a 20K resistor. 3.5 amps, add a 35K resistor etc.

Thanks LeeWay, But you ALSO are missing my point:

The full size Geckos cannot run motors that will draw more than 7 amps. Their setting for 7 amps is NO limit resistor, so there is no protection for a motor of greater than 7 amps.

Apparently, using a motor rated for MORE than the max Gecko amps (7) will harm even the 203V.

So my question concerns the G250/251/G540: CAN I use a motor rated for more than 3.5 amps? (And will the drive limit the current to only 3.5A?) Or, like the larger Geckos, will this cook the drive?

I'm hoping Mariss or Marcus will answer this.

CR.

I'm hoping Mariss or Marcus will answer this.

CR.

??

[eman5oh]

The the 201 or 203 or any of the "full size" Gecko stepper drives with no resistor = 7 amps to the motor. Use a 10 amp motor and it will receive 7 amps. It will have aprox. 70% of the rated torque. No harm will be done to the drive.

Mariss or Marcus will have to reply, as to what happens when you place 4.5k resistor in the drive to set it to 4.5 amps. I suspect they have limited the output to 3.5 amps regardless of how big a resistor you place in the drive.

Thanks Gerry! But I think you are missing my point:

The full size Geckos cannot run motors that will draw more than 7 amps. Their setting for 7 amps is NO limit resistor, so there is no protection for a motor of greater than 7 amps.

Apparently, using a motor rated for MORE than the max Gecko amps (7) will harm even the 203V.

So my question concerns the G250/251/G540: CAN I use a motor rated for more than 3.5 amps? (And will the drive limit the current to only 3.5A?) Or, like the larger Geckos, will this cook the drive?

I'm hoping Mariss or Marcus will answer this.

CR.

[Crevice Reamer]

Yes! I would HOPE so. I would like to hear it from Gecko though.

CR.

[eman5oh]

I should add if you use a motor rated for more than 3.5 amps the drive when set to 3.5 amps, will run the motor at 3.5 amps regardless of what the name plate of the motor states. Bigger motors preform at less that full rated torque. The current setting resitor dose just that sets the current the drive outputs to the motor, regardless of what motor is hooked up.

[Crevice Reamer]

Yes! I would HOPE so. I would like to hear it from Gecko though.

CR.

?

[Mariss Freimanis]

Thanks Gerry! But I think you are missing my point:

The full size Geckos cannot run motors that will draw more than 7 amps. Their setting for 7 amps is NO limit resistor, so there is no protection for a motor of greater than 7 amps.

Apparently, using a motor rated for MORE than the max Gecko amps (7) will harm even the 203V.

So my question concerns the G250/251/G540: CAN I use a motor rated for more than 3.5 amps? (And will the drive limit the current to only 3.5A?) Or, like the larger Geckos, will this cook the drive?

I'm hoping Mariss or Marcus will answer this.

CR.

The G250/G251 is like our other drives. No current set resistor results in the drive outputting its maximum rated current, 3.5A in this case.

Generally it's not a good idea to run a step motor at much lower (<70%) than rated current. Besides degrading low speed torque, it can also adversely affect high speed torque.

Mariss

[Crevice Reamer]

The G250/G251 is like our other drives. No current set resistor results in the drive outputting its maximum rated current, 3.5A in this case.

Generally it's not a good idea to run a step motor at much lower (<70%) than rated current. Besides degrading low speed torque, it can also adversely affect high speed torque.

Mariss

Right now, there aren't many stepper motors that will fit the voltage and current limits of the cheap drives without exceeding at least one.

So these warnings mean nothing? They can safely be ignored without harm to the drives?

The motor’s rated phase current must not be more than 7 Amps.

Sounds pretty serious to me!

PLEASE READ FIRST BEFORE USING THE G201
Before you start, you must have a suitable step motor, a DC power supply suitable for the motor and a current set resistor. The motor’s rated phase current must be between 0.3 Amp and 7 Amps. The power supply voltage must be between 4 times and 20 times the motor’s rated voltage. The current set resistor may be a 1/4 Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

PLEASE READ FIRST BEFORE USING THE G202
Before you start, you must have a suitable step motor, a DC power supply suitable for the motor and a current set resistor. The motor’s rated phase current must be between 0.3 Amp and 7 Amps. The power supply voltage must be between 4 times and 20 times the motor’s rated voltage. The current set resistor may be a 1/4 Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

PLEASE READ FIRST BEFORE USING THE G203V
Before you start you must have a 2-phase hybrid PM step motor, a DC power supply suitable for the motor and a current set resistor. The motor’s rated phase current must not be more than 7 Amps. The power supply voltage must be between 15VDC and 80VDC unregulated. The current set resistor may be a 1/4-Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

PLEASE READ FIRST BEFORE USING THE G210
Before you start, you must have a suitable step motor, a DC power supply suitable for the motor and a current set resistor. The motor’s rated phase current must be between 1A and 7A, or 0.3A to 2A for the low current range. The power supply voltage must be between 4 times and 20 times the motor’s rated voltage. The current set resistor may be a 1/4 Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

PLEASE READ FIRST BEFORE USING THE G212
Before you start, you must have a suitable step motor, a DC power supply suitable for the motor and a current set resistor. The motor’s rated phase current must be between 1A and 7A, or 0.3A to 2A for the low current range. The power supply voltage must be between 4 times and 20 times the motor’s rated voltage. The current set resistor may be a 1/4 Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

CR.

[LeeWay]

Maybe not too many Nema 34's but there appear to be plenty of 23's that these will work with. I have 3 small machines right now and none have bigger than 23's yet. The mill will soon, but none are running over 3 amps right now. The mill is running on 72 VDC though. The lathe is 48 VDC and the router is 62 VDC, but both those supplies are adjustable.

I would say to heed those warnings on those particular drives and wait until the literature gets finalized and published for these before trying to cover the 250's with that blanket.

BTW, I wasn't missing the point, I don't think. You have to sharpen your pencil before it gets a point on it. Apparently I just wasn't understanding the question.

[Crevice Reamer]

Okay! I agree. I may not have stated the question in the most understandable manner.

But can you please show me some decent size (250-400 oz) steppers that run best at 50 volts, but don't exceed 3.5 Amps? I would be delighted to see them.

CR.

[Mariss Freimanis]

Running at less than rated phase current will not hurt the drive and it will not hurt the motor. The only effect will be sub-par torque; always at low speeds, possibly at high speeds if the set current is less than 50% of rated.

FYI: The median step motor current is 3A. As many are rated at less than 3A as are rated at more than 3A. We commissioned a market study last year to find that out as well as other things.

Mariss

[tauntdesigns]

Okay! I agree. I may not have stated the question in the most understandable manner.

But can you please show me some decent size (250-400 oz) steppers that run best at 50 volts, but don't exceed 3.5 Amps? I would be delighted to see them.

CR.

Hi CR,

These are not perfect, but are close..........
nema23 276oz/in 2.8amp, 3.08v
nema34 434oz/in 2.8amp, 3.108v
http://web2.automationdirect.com/adc...ors_-z-_Cables

From the quote above, it looks like you would like a motor: 2.5v and under 3.5amp

Happy searching,
Jack

[LeeWay]

Almost all the Nema 23's at Keling would work fine with these drives. The two largest ones, which I have running on 203's now wouldn't be able to use the voltage I am putting through to them, but they would still work fine @ 50 VDC and 3 amps.
I am running the 425's on my router with an adjustable lab supply @ 62 VDC. The 495's I'm running on the mill @ 72 VDC. Less than that actually. Probably more like 68 VDC.
The 270's on the lathe are running just under 3 amps on 48 VDC.

I will be upgrading my mill motors to Nema 34's and use the 495's on a plasma cutter or stick them on my router.
I won't be trading in my 201's or my 203's.

[Mariss Freimanis]

I looked at the NEMA-23 motors. The 166 in-oz motor motor is 2.36 mH, the 276 in-oz motor is 3.82 mH. Both are 2.8A per phase. Using Vmax = 32 SQRT mH, I get 49VDC and 62VDC respectively as the maximum power supply voltages.

Assuming a 10 TPI screw and using Lbs = pi * TPI * in-oz / 8, I get 651 Lbs of low-speed thrust for the 166 in-oz motor and 1,083 Lbs thrust for the 276 in-oz motor. That's 1/3 and 1/2 ton thrust respectively. That should be enough to bend and break things either way.

The smaller motor will hold low speed torque to a calculated 1,445 RPM while the larger one will reach a calculated 893 RPM before torque begins to drop using a 50VDC supply. The calculated power output is 125W and 130W respectively at 50VDC*.

The smaller motor will be tooling along at 144 IPM, the larger at 89 IPM before torque even begins to drop off. Both motors will reach 3,000 RPM (300 IPM) with usable torque remaining. If these performance calculations aren't sufficient, you need a 6A to 7A NEMA-34 motor run at 80VDC.

These are little drives; two of them can fit on the back of a NEMA-23 motor with a lot of room left over. They are 5% of the volume and 1% of the weight of a NEMA-23 motor. Each delivers as much power as a 90W RMS per channel, 180W RMS total stereo amplifier. They will leave a big impression when coupled to NEMA-23 motor; they will warm it right up and make it sing.:-)

Mariss

* Calculations based on some new equations I'm deriving for calculating motor power output and corner frequency speed.

[tauntdesigns]

Mariss, Thank you for checking those out.

I'll be up all night with the calculator trying to duplicate those numbers.

Cheers,
Jack

[dansutula]

So... any suggestions for the best (lowest cost / highest performance) power supply for a G540 and the Nema 23 motors? After the amazing "value engineering" feat that Marris has achieved, it would be a bloody shame to overpay for a power supply or settle for sub-optimal performance.
Regards,
Dan

[Crevice Reamer]

So... any suggestions for the best (lowest cost / highest performance) power supply for a G540 and the Nema 23 motors? After the amazing "value engineering" feat that Marris has achieved, it would be a bloody shame to overpay for a power supply or settle for sub-optimal performance.
Regards,
Dan

The $60 48V/7.3A Keling PS can power up to 11A of motors and should be a good candidate:

http://kelinginc.net/SwitchingPowerSupply.html

CR.