AC Servo Questions

[curtisturner]

I am currently using DC Bruch Servo's
But thinking of building another machine and want to use AC Brushless Servo's

Here is a couple of questions

1. What are the benifits over DC Brush ?
2. Can I use one name brand of servo and another brand Drive ?
3. Do the have to match up volts and amps exactly ?
4. Can I use a 400W Servo (230v 1 ph 2.8 Amp) with a 750W Drive (230v 1ph 4.4Amp)

5. Do almost all drives offer step and direction inputs ?

Thanks
Curtis-

[Al_The_Man]

1. What are the benifits over DC Brush ?
2. Can I use one name brand of servo and another brand Drive ?
3. Do the have to match up volts and amps exactly ?
4. Can I use a 400W Servo (230v 1 ph 2.8 Amp) with a 750W Drive (230v 1ph 4.4Amp)

5. Do almost all drives offer step and direction inputs ?
-

1/ DC Brushless and AC servo's have no brushes to wear, are generally lower inertia, have potentially higher max. rpm, and can disipate heat better due to the windings being wound on the stator.
2/ Mix and match is possible with DCBL and AC, but are much harder to match up due to different forms of commutation etc DCBL is the easier of the two.
3/ voltage rating of the amplifier can be higher and current should be at least equal.
4/ In most cases, yes, providing the current limit can be set accordingly.
5/ Not almost all, some, if analogue or digital, you will need a step/direction convertor, I believe there is one featured on the zone here.
Al.

[daedalus]

Looks like Al beat me to it.

2) sanyo denki P5 range are very popular motors, mainly because a truckload were sold for next to nothing through a surplus house a year back.

There is a drive developed by someone on the forum which is now commercially available. Think they go by the name of granite devices now. http://www.granitedevices.fi/index.php?id=8

3) you can run a servo with less voltage than rating, but its max speed will be limited. You can run a servo with less current available, but this will limit its rated torque.

The only thing you have to be careful is that you dont provide large reserves of current, as should the motor stall it will draw its stall current, many times its continuous current, and if this continues for more then a few seconds the coils will overheat. This is what a fuse is for, to provide something cheap and replacable to burn out in such a situation.

4) yes, but you need to make sure that should the 400w servo stall it doesnt recieve a large continuous current. Most drives provide current limiting, just make sure the current limiter is set correctly. (not sure what you mean here, as you are talking about brushed dc servo, and this post is asking about brushless motors). Again you can add fuses on the dc bus before the drive to provide protection.

5) not all, some take 10->-10v analog (both position controlled, and torque controlled), others take pwm and direction (usually torque controlled). Step + Dir is more common on hobbyist hardware, and virtually noexistant on industrial drives. (the drive i mentioned takes step dir + others).

Luckily you can get cheap pcbs which produce analog command signals from step + dir.

[curtisturner]

Here is the main question

I have a 750 watt YASKAWA SERVO PACK AC DRIVE 0-230V 4.4 AMP
and a 400 watt YASKAWA AC SERVO MOTOR 0-230V 2.6 AMP

I wanted someone to confirm they would work together ?


Thanks
Curtis-

[daedalus]

they should, but like i said you need to be careful. Should the servo stall it will draw something around 8A, which is enough to cook the coils in a short time. This can be prevented easily by fusing the drive at a current rating between running current (continous) and stall current. Your spec sheet for the motor should specify three currents, continous, peak, and stall.

[curtisturner]

Al the Man where can I find more info on the step/direction converter?
Do you know If I will need one for a Yaskawa SGDA-08AS servo pack drive

[Al_The_Man]

I am not that familiar with that particular drive but I believe Yaskawa seldom use step/dir if at all, but the manual will tell you and you will need that to set it up, most likely.
Do a search here for the Pixie p100 convertor, I believe that is the name of the step/dir to analog convertor.
http://www.skyko.com/products/
Al.

[curtisturner]

For future purchases, what name brand do you suggest that would come standard with step / dir inputs ?



Thanks
Curtis

[Al_The_Man]

I don't use step/dir drives, only analog and digital, so Maybe not the best to answer, There is a member here who has developed a AC drive which I believe is step/dir input search for posts by XERXES.
Al.