Versatile Servo Drive VSD-A

[Xerxes]

I'm proud to present the results of the new servo drive development project from CNCzone forums! This project started in the forum over a year ago and the goal was no less than to develop a professional quality and performance servo drive with hobbyist level pricing.

In a nutshell, it is a single axis universal step/dir capable drive for DC/BLDC/AC servo motors with output capability of 12.5 Amps and input voltage range of 24-200 Vdc. For detailed specifications, please see the product page:

Fluxeon VSD-A specifications:
http://www.granitedevices.fi/index.php?id=8
See also a short video clip showing VSD-A running AC servo motor:
http://video.google.com/videoplay?do...92974890836012


What makes this drive performance so good?

Fluxeon implements fully tunable field oriented flux vector torque control that has become an industry standard in top class AC servo drives. Vector control has been typically available only in much more expensive drives.

Fluxeon has been built around a high performance 60 MHz digital signal controller with 12 bit AD converter for precise, quiet and maximum troughput control.

Fluxeon features also tunable acceleration and velocity feedforward paths for quicker response. Feedforward means direct path from commanded position input to motor torque output. In other words, feedforward eliminates the most position error before it even starts forming. A smaller residual position error is being corrected by a standard 32 bit PID feedback loop.


Why torque control is so important?

Torque control is an essential part of servo controls since motor position can be controlled ONLY by adjusting shaft torque. Most (if not all) low cost drives have no closed loop torque control. Instead these drives are based on voltage control which produces sluggish torque response mostly because of the effect of motor winding inductance.

In voltage control mode, the torque bandwidth is typically around 30-80 Hz (derived from motor inductance and resistance). In comparison, a closed loop torque control typically reaches 1500-3000 Hz bandwidth. Higher bandwidth makes it possible to use higher feedback gains to achieve stiffer and more precise position control.


Other key benefits compared to same price competitors

-Firmware (drive's internal software) upgradeable by user
-Easy set-up with guided tuning PC software
-Optional velocity mode for spindle use
-Arbitrary ratio input scaling and gearing (step multiplier/divider)
-High speed optoisolated inputs: up to 330 kHz step rate with standard optoisolator, and up to 2 MHz with socketet replacement
-One drive to rule them all: supports brushed DC, brushless DC and AC servo motors. Upgrade motors without need to replace drives.


Pricing

An introductory price of Fluxeon VSD-A is 150 EUR. This offer is valid for the batch of the first 100 units. Drives are available immediately and most are shipped within couple of work days after payments have been received. To ask details or to place order, please contact us at these email addresses:




About us

Granite Devices is a Finnish company that was found to produce this particular drive and develop this technology even further. Fluxeon VSD-A drives are made in Finland under high qualitity standards. We give 12 month warranty to our drives.


Best Regards,
Tero

[DennisCNC]

Great work!!!

[skullworks]

Looks promising. If there were a good small AC servo in the 2hp range that could be used as a spindle motor I'd be thrilled.

[Xerxes]

Ebay is full of that range motors :-)

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Would it be helpful if I compiled a table about facts of different drives? I think that would help comparison.

[Xerxes]

Here is the comparison of several drives. Let me know if you find a mistake or if there is something I should add. I tried to pick the most important features for CNC use.

[rkonnen]

Is the specs you have given for peak current with or with out heat sink?If with out will adding heat sink to drive allow it to hit a higher peak current ?
Thanks,
Richard Konnen

[Xerxes]

VSD-A has one kind of dynamic current limit to utilize power stage more efficiently:

-12.5 Amps are both peak and continous current in AC mode if output frequency is greater than than 50Hz.
-In DC operation max contininuous is 10 Amps and 12.5 A peak. In DC mode with 10A limit the max cont. power equals 1760 Watts.

I can adjust those limits in firmware upgrades if it seems that that those were too "careful" limits (power stage rating is 20A cont and 40A peak). I'm maximizing reliability by using quite high safety margins (thats where Granite comes :-)

[pdunster]

Looks like a nice drive! What will the final price be after the "Introductory offer"?

BTW, the price you have for the CNC Teknix Tekdrive is incorrect, you have used the Aus$ value including local tax, the correct price in US$ is aprox $236 (rates fluctuate!).

Cheers
Pete

[the4thseal]

do you use a break out board to talk to it and if so which one do you recomend?

[Xerxes]

Pete, the final price is still undecided. But the fact is that we can't operate very long with 150 eur price. The drive is probably more expensive to manufacture and has more expensive components than many of compared drives so it would be crazy to sell it cheaper than those DC drives. The intro price barely covers the costs during the first 100 units

We may end up in some kind of dual pricing. Separate "sponsored" price for hobbyists and "normal" price for industry. That way it will still be very competetive in both sectors.

Thank you for pointing out the aus dollar difference. I'll correct the table.

--

the4thseal,
Any step/dir breakout board should be fine. I have a simple design of VSD-A specific board which is still untested. I can put the PCB files somewhere if someone wants to try it.

[rkonnen]

I think a 25% safety margin would be plenty. Setting the drives at 15A/30A.
Best regards,
Richard Konnen

-12.5 Amps are both peak and continous current in AC mode if output frequency is greater than than 50Hz.
-In DC operation max contininuous is 10 Amps and 12.5 A peak. In DC mode with 10A limit the max cont. power equals 1760 Watts.

I can adjust those limits in firmware upgrades if it seems that that those were too "careful" limits (power stage rating is 20A cont and 40A peak). I'm maximizing reliability by using quite high safety margins (thats where Granite comes :-)[/QUOTE]

[Xerxes]

I used manufacuter's documentation when choosing a proper current limit. However, every sold drive has been tested using 15A stall current and all of them have passed.

According to component specs, the maximum safe current depends significantly on switching frequency because switching losses are directly proportional to frequency. I'm planning to add an option for 7.5 kHz switching freq which should allow about 20-25% increase in current limits.

I think 25% margin would get very close to breakdown level in hard conditions (high temperature & frequency & voltage). Ratings in front page of semiconductor data sheets should be taken very carefully.