VSD-A / VSD-E users : I need your support about stepper motors!

[sunmix]

Hello everyone,

I have been planning to purchase a VSD-E, as Tero said that servo stepper is available, and will be improved at later firmware versions.

Now - During my past, I have been meddling around with stepper motors, ranging from 200 oz/in to 1810 oz/in, I have been using G201, G202, and G203V, and my first wiring knowledge comes from CampbellDesign's How to Build A Power Supply : http://campbelldesigns.net/files/pow...ply-part-1.pdf

and I have been using it happily ever since =)

Now I will try out VSD-E on servo stepper mode, which means a stepper coupled with an encoder, very soon.

But reading back in the Campbell's Power Supply PDF, it says that I need to supply 20 times the rated voltage, and multiply it with 67%. Supposedly I'm using KelingINC's 1810oz/in, the phase voltage is 6.6volts, which means:

6.6VDC x 20 times = 132VDC.
132VDC x 67% = which is 88.44volts.

Then I'm using a 600W for that setup, at 59VDC, which means a lower utilization of max stepper speed.

88.44volts is the 100% utilization of the max stepper speed.

I remember Mariss said 55volts is the best for steppers, but that is for Geckodrive's products.

I'm trying to say that - I'm worried that once I use VSD-E, I won't get good torques from my 1810oz/in stepper.

Anyone used VSD-A or VSD-E with stepper before? How was your power configuration? How was the stepper perfomance? Did it lose torque or RPM?

Like in the VSD-E Manual, it doesn't specify about times 20 of the voltage phase and reduce it to 67%. Should I use the Campbell formula, or the VSD-E formula?

Charles

[Xerxes]

Hi,

The 20x rule is not absolute limit with VSD-E since it uses more advanced (recirculating) PWM output, which leads to less motor heating. Additionally in servo mode, the motor heating is really low. I'd say up to 25-35X could be used, or any lower ratio.

For maximum continuous torque, perfectly matching stepper has 7A current rating and as low as possible voltage. On other hand, up to 20A stepper could be used since drive can deliver 20A peak current in servo mode. Higher than 7A motor probably would be best for highest speed.

[Oleks]

another case:
I purchased VSD-A drives year ago and during thinking/gathering all mechanic stuff for MechMate CNC router switched to go with PK299-F4.5A or like 2-Phase Stepping Motors (in preferred unipolar half-coil mode - 4.5A, 2.5mH/phase, 600 oz/in). I read forum but it's still not quite clear for me - what limitations/differencies VSD-A has compared to VSD-E and (probably both A,E) compared to common stepper dedicated drives? I need at last 350 oz/in from the motor. May be there is possibility to update firmware to E's stepper features? Currently driving steppers without encoders not supported in both A, E?

Other options - have to buy four VSD-E drives (~ $1380 for encoders+drives/Interface Board/shipping) or Gecko 203v(~ $780 for drives/Interface Board/shipping) or probably wait a bit for VSD-Core?

[Xerxes]

If you need open loop stepper drives quickly, I'd use Geckos. This is because the official VSD-E stepper firmware is not yet done. Once the firmware is ready it will be superior to any traditional stepper drive (in open loop & closed loop).

Stepper can be already operated as AC servo with VSD-E but in that mode voltage limits speed more than in the stepper optimized firmware. To test max speed in this mode, put a rectifier and capacitor in step motor leads and measure rectified voltage while rotating motor. When voltage reaches ~70VDC, you're rotating it at the top speed limit. The new firmware should improve top speed by ~2-4X factor.

Higher than 20X voltage ratio can be used with VSD's since it uses optimal recirculating current control which significantly reduces motor heating. In theory there is no limit, but I wouldn't go above 30-40X.

[Oleks]

No, I'm not in a harry. Just if VSD-A some day this year would work with open loop - no need for me to buy anything to have router making money. After that I can upgrade to servo or rather start second with servomotors. That's why I want to stick to VSD drives only and don't mess with other brand.