3V steppers on 28V 36A power supply

[jeroenvw]

I need advice on the wiring of the steppers, FET4 driver board and power supply.

I have been reading a lot of threads here at CNCZone.com about steppers,
and from what I understand steppers perform best wit 10 to 20 times the rated voltage.

But when I calculate the resistor needed for my configuration, I need a 150 watt resistor!
It seems to me that (almost)all the extra energy I send to the steppers is wasted as heat from the resistor, so what's the point of increasing the voltage?

I contacted stepperworld.com (the manufacturer of the FET4 driver board), and they say I should run the steppers on a 5 volt power supply. But I think I won't get good performance from my steppers with this low voltage.

Can someone please help me with this??
Please see the pictures of the calculations below.


Power Supply:
Abbott Power Supply
28 V DC Regulated
36 Amps

Steppers:
KELING KL23HM276-30-8B
2,76V
3,0A


When I use the steppercalc tool, this is the result :
<See uploaded image 1.jpg>

But there are no 156 W resistors for sale, so I should use 2 resistors.
That brings the resistor wattage down to 78 watts. See picture:
<See uploaded image 2.jpg>

I can only buy 100Watt resistors, but this is not a problem right????
Do I need two 8.67 Ohm resistors, or do I need two 4.33 Ohm resistors??
<See uploaded image 3.jpg>

How do i connect the two resistors?
The red lines represent my solution.
Can someone please verify the resistors are connected correctly??

Thanks!!

[Madclicker]

The waste heat is the big drawback of non-choppered drives. You need the higher voltage to overcome the inductance of the motor. Otherwise you are limited on speed.

Use 2 8.67 in parallel or 2 2.8 in series.

I would, and did, choose a chopped drive after someone pointed out this very serious drawback.

[jeroenvw]

Originally Posted by Madclicker The waste heat is the big drawback of non-choppered drives. You need the higher voltage to overcome the inductance of the motor. Otherwise you are limited on speed. Use 2 8.67 in parallel or 2 2.8 in series. I would, and did, choose a chopped drive after someone pointed out this very serious drawback.

You say "non-choppered drives". Do you mean the stepper motor, or the driver board? > Never mind this question, I ded some research and found out that the driver boards can be chopper drives.

[jeroenvw]

I am thinking about buying a xylotex board... but then I have to get rid of the 175$ FET4 board.
I have asked stepperworld.com for a refund, but I can imagine they will deny that request.

The xylotex looks like a perfect match. It can handle 35V, my power supply is 28 volts. Its a chopper driver, and it does microstepping. The only thing that worries me is that it can handle up to 2,5Amps, and my drives are 3Amps/phase.

[dertsap]

the fet boards work not as well as the chopper drivers but they do work well , connect dual resisters , you can get them off ebay cheap cheap cheap , ive got the fet3 board , ive since upgraded to geckos , which can handle far more amperage than the alternatives and the fet boards can handle high amps as well , i would suggest if you are planning on buying a chopper driver ,think about what you want to have in the future , maybe larger motors ? the gecko is by far the best choice in my opinion , costs a little more but at least you would only have one driver board sitting on the shelf collecting dust rather than 2 if you decide to upgrade

[jeroenvw]

First the good news : Stepperworld.com agreed on the refund of the FET4 driver board!!
These guys are really nice over there. They have been very helpfull in answering questions in the past too.
Very very nice.

Well, I think the Gecko's are very expensive compared to the xylotex.
If I take the most simple Gecko, the G201, it will cost me $456 for a 4 axis setup! The xylotex only costs less than half that amount, $185.

[jeffs555]

The Gecko's are nice drives, and do have other advantages like higher voltage rating, and mid-band resonance compensation. However, if you are concerned about cost, you could just go with the Xylotex and run the motors at 2.5 amps. The static torque is directly proportional to the current, so the static torque would be only about 83% of the rated torque, but static torque is not usually a problem. The maximum speed without losing steps is usually the problem, and at higher speeds there should be almost no torque difference between running at 3 amps and running at 2.5 amps.

[jeroenvw]

Check out this link at xylotex : http://www.xylotex.com/497ozin.htm These are also 3Amp steppers that they sell in combination with the xylotex board.

[jeroenvw]

Hmmm it seems it's very difficult to get the xylotex boards shipped to Europe because of some law about the lead in the soldering. Now what...

Maybe I should go with the hobbycnc board, it has about the same specs of the xylotex. I rather prefer the xylotex... anybody knows who to get the xylotex board to Europe??

[jeffs555]

Just looked at the specs for your motors, and 3 amps is the unipolar current. The bipolar parallel current is 4.2 amps, so the static torque with the 2.5 amp Xylotex would be less than using the unipolar Hobbycnc at 3 amps. For those motors, the Hobbycnc would probably be the better choice.

[jeroenvw]

Jeffs555, thank you for pointing that out.
I asked HobbyCNC if they can provide a fully assembled board, I am not a really experienced soldering guy If they can't / won't, I'll still give it a shot thoug.

[jeroenvw]

I just ordered the HobbyCNC driver board.!!
I think it has a very good value for the money. Now I have to wait for about 2 weeks... shipment to The Netherlands (Europe) always takes long due to customs.

Everybody who contributed to this topic, thanks for the help and the good advice!