Power Supply Question

[NVTS]

I am in the process of trying to figure the proper PS for the motor and drivers that I will be using on my 4x8 build. Any help or suggestions would be great.

Below are the specs on the motor, driver and power supplies that I have available.

Motor: Will be using 4 motors

Frame Size:NEMA34
Step Angle: 1.8 degree
Voltage: 6.4V
Current: 2.8A/phase
Resistance:1.6Ohm/phase
Inductance:15mH/phase
Holding torque: 6.4N.cm with bipolar connection for 892oz-in holding torque
Number of wire leads: 8
Weight: 3.6 kg
Length: 94mm

Driver: Will be using 4 drivers

Parameters: Min, Typical, Max, Unit
Output current: 1.29, -, 5.86, A
Supply voltage(DC): 20, 68, 80, VDC
Logic signal current 6, 10, 30, mA
Pulse input frequency 0, -, 200, KHz
Isolation resistance 500, -, -, MΩ


Power Supplies: Plan on using 2. One PS for 2 drivers.

1. 350W, 24V, 14.6A
2. 350W, 27V, 13A
3. 350W, 48V, 7.3A

I have a separate 5V power supply for the breakout board.

Cheers,

Howard

[dertsap]

in order to get the motors up to a decent speed then you'll need to run at high voltage , so I wouldn't hesitate to go with the 48v

[NVTS]

dertsap,

That was my thinking also. I was l thinking about a 72vdc 20amp power supply. But it seems that alot of kits have the 48vdc with similiar drivers.

Think that the 72vdc is better?

Cheers,

Howard

[dertsap]

if you got a line on a 72v then go with that , the reason that they give 48v supplies in kits is because they are cheaper and will get low voltage motors up to speed , the 72v supply will get you basically to 1/2 of what the motors can run to (but not the drivers) , so the max sized supply that your drivers will accept will be your best bet ,

if the 72v supplies are too expensive then most ebay 36v supplies are cheap and can be run in series , that will get you to 72v as well , just a bit more bulk to the setup

.

[dertsap]

two of these together would suffice and would be cheap , as long as they can run in series
http://cgi.ebay.com/Regulated-Switch...item2c566367bf

[NVTS]

dertsap,

Should I have a PS per driver?

Cheers...

Howard

[dertsap]

a single 10 amp supply for all three will be plenty of power

[CarveOne]

My G203V drives have a maximum input spec of 80V. 72vdc is about as close to 80vdc as you can get with any amount of margin left (just 8vdc) for ac line voltage surges. A 65vdc PSU is the next lower voltage level that will be a good choice for these drives.

Whatever your maximum input voltage is for your drives should determine which voltage PSU that you should choose. Step motors usually can handle more than most drives.

The Gecko drive website has some guidelines that describe this in more detail, such as formulas to determine what your motors can safely use.

CarveOne

[NVTS]

My drivers have a 80w max , 20w min. So 48w will work well, but a 65 psu will be the best?

So, one power supply for 2 drivers is a good setup?

Thanks for all the reply's.

Cheers...

Howard

[CarveOne]

Originally Posted by NVTS My drivers have a 80w max , 20w min. So 48w will work well, but a 65 psu will be the best? So, one power supply for 2 drivers is a good setup? Thanks for all the reply's. Cheers... Howard

You're confusing watts and voltage above. For the driver example I gave, 72vdc PSU is the maximum voltage commonly available in a linear type power supply that is safe to use with the G203V drivers. The linear power supplies are not regulated, so the output voltage goes up by some amount with an ac line voltage surge. Keling sells a 65vdc linear power supply that is the next step higher than 48vdc, but is lower than 72vdc. It will run your motors a bit faster than with 48vdc and will have more margin for any ac line surges if that is what you want. I don't have line surge problems except during electrical storm, and the CNC equipment is not running then.

The driver specs that you posted earlier shows 80vdc input but you didn't say which vendor and model driver. It appears to me that the 72vdc PSU may work fine as long as your motors can also handle 72vdc without getting too hot. Gecko's site has a formula for calculating it.

One power supply for 1, 2, 3, 4, 5, or 6 drivers is a good setup as long as the total current draw from the power supply isn't exceeded. I run four Keling 495 oz-in NEMA23 motors from one Keling 72vdc 20amp PSU, and it's loafing along at less than half the PSU current rating. 2 motors on the X axis, 1 on the Y axis, 1 on the Z axis. The gantry is approaching 175 pounds. The working area is 50" x 136".

CarveOne

[NVTS]

Carveone,

Sorry. I typed in w instead of vdc. Thanks for the info and I am reading the Gecko site.

Thanks for the info. With your 495oz/in setup and the size of your cutting area and gantry weight, is close to what I will be having.

I assumed that I would need the larger motors oz/in for a larger table and gantry weight.

What type of ipm are you cutting at (rough and finish).

Again, Thanks to all for the help.

Howard

[CarveOne]

Originally Posted by NVTS Carveone, Sorry. I typed in w instead of vdc. Thanks for the info and I am reading the Gecko site. Thanks for the info. With your 495oz/in setup and the size of your cutting area and gantry weight, is close to what I will be having. I assumed that I would need the larger motors oz/in for a larger table and gantry weight. What type of ipm are you cutting at (rough and finish). Again, Thanks to all for the help. Howard

Yeah, I figured that was the case. I got too wordy, but wanted to be sure that you understand that this stuff isn't all set in stone. There are a lot of variables and it can get overwhelming even tor the technically savvy folks. The G203V has a dc input fuse that blows in order to protect the driver components if a surge goes too high. Some other driver designs may not have that feature. The fuse is surface mounted. It will cost a trip back to Gecko for the replacement fuse unless you have the knowledge and equipment to replace it yourself.

My machine is jogging at 1,400 IPM on X and Y. (R&P) The Z has a 1/2-10 5 start ACME screw with 8.5" travel. It goes over 600 IPM but there is not enough travel to see where it will peak at. The stuff I have cut has been limited to 100-150 IPM because of the bit and material considerations. There has been gantry racking issues due to weak corner joints where the rail and beam meet the riser supports. A fix is underway and I'm waiting on delivery of some steel to correct it on Tuesday (I hope).

I haven't cut a lot of stuff so far, for continually rebuilding something that I don't like about it, or expanding it. There is one photo frame example over in the Sign Making forum, and there are three "CarveOne" videos on YouTube. My build log is over in the Woodworking Machines Build Logs forum.

CarveOne