Need advice on Brushless AC servo drive

[panaceabea]

Need advice/reccomendations on brushless ac servo drive. I am retrofitting a large cnc lathe with GE brushless ac servos 66in lb , aprox 2kw .

I have purchased a couple of the sva 2300 ac drives from automation direct but in talking with their tec dept today I was told their drives would only work with their motors and encoders and it would not be possible to use them with the GE motors as there is no way to change the encoder input type to work with the GE encoders (BEI e25) .

Any thoughts advize or help greatly appreciated , I would rather not have to purchase new cable motors etc.

[Al_The_Man]

You need to know the nature of the motors, are they DC brushless or AC sinusoidal etc, what type of feed back system is on them, Hall effect? Encoder? Resolver? This determines the type of drive you can use and also what type of command signal do you intend using to input to the drives? Analogue? Digital? Step/Dir?
Al.

[panaceabea]

They are brushless AC 3 phase from GE , with BEI E25 encoders.
here is the data sheet on the encoders http://www.thompsonmachine.net/encoder.pdf
and here is the data plate on the motor http://www.thompsonmachine.net/m.jpg

Plan is to use step and direction input from mach 3 via the c10 breakout board from cnc4pc , same setup I am using on 5 other machines in the shop currently

[Al_The_Man]

That shows the differential encoder, which I suspect is used solely for position feedback to the drive, the motor plate does not indicate what type of commutation feedback might be present.
The motor itself may have to be examined to see what type, if any, of other feedback method.
Al.

[panaceabea]

what am I looking for on the motor to detirmine the method of commutation feedback ? In addition to the 3 power leads coming from the motor there is a two conducter wire . Anyway to determine with a VOM or scope?

[Al_The_Man]

It is possible they may have used the encoder for commutation? test the continuity on the 2 leads from the motor, if very low resistance, virtually short circuit, they may be temperature sensor.
Al.

[panaceabea]

pulled the little cover to check the other two leads and the wiring diagram inside list them as "thermostat" , sticker inside says "3 phase 230volt AC 5 wire with thermostat, general electric automation division , virginia"

I would like to use these existing motors , not so much from a cost standpoint but the fact that they are mounted, wires are pulled all the way to the cabinet , and the one on the x axis takes most of a day to get to .

would it be possible to use these with a common drive with a simple change of encoder .

Do you know what type encoder would be needed to work with the drives from automation direct and if its at all possible to adapt these motors to work with the AutDirect drive?

[Al_The_Man]

There is a bit of a puzzle on those motors, They look like older GE, in fact older to be AC sinusoidal servo's. For modern drives, you may have to add hall equivalent encoder or resolvers, but the pole count of the motor would have to be obtained, probably easiest by 'scope.
What would be approximately the original date of manufacture of the lathe?
Al.

[H.O]

Hi,
Have you looked at the VSD-A from Granite Devices? It will drive brushless AC, brusless DC and brushed DC servos at up to 200V with differential encoder as the only feedback element - no resolver or hall sensors needed for commutation.

The drive puts out 10A continous/15A peak. I don't see a current rating on the motor plate so I don't know, perhaps its to small.

Tero (aka Xerxes here on the zone) is very helpful and responsive, drop him a line and he'll give you all the info you need.

(Usual disclaimer....)

/Henrik.

[panaceabea]

The lathe has a manufacture date of 7/1989 the motors show an inspection date of 5/1986

[Al_The_Man]

May be the way to go to check out the Granite drives, especially if there is only differential encoder fitted.
I have not used them personally.
Al.

[panaceabea]

I have no problem fitting a different encoder from renco or BEI if thats all thats needed to use these with a commonly avail drive