RE: [CAD_CAM_EDM_DRO] Servo Motor & Driver

VR could mean all sorts of things. It is a term highly misused, some people
have referred to a normal DC servo motor as being variable reluctance, and
it is sort of arguable but not really correct. Some AC servo motors have
compound stators so their reluctance does truly vary with speed, and perhaps
the same could be applied to a DC servo, these would have exceptional torque
at low rpm's. Then there are true variable reluctance where the reluctance
can be controlled, don't remember much about them, but I do remember they
exist, or at least did on paper when I was a college.

If your servo's are good and you can find out how to control them keep them
as is, based on recent experience with other products I am fairly confident
it will be far superior than most of the alternatives.



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Weedy Tan
Sent: 18 June 2007 10:38
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Servo Motor & Driver



Hi Mark,

Thanks for the advice. I was in touch with Servo Products who made the
"Servo Motor" but was referred to another company who bought over their CNC
operations. I am still waiting for their response.

The "Servo Motor" is supposed to be a special VR (for Variable Reluctance,
whatever that means :) motor. Do you have any idea if it is an actual servo
motor or a special stepper motor as someone who has the same motor was
pointing out?

Kind regards,
WT

----- Original Message ----
From: Mark Vaughan <mark@.... <mailto:mark%40vil.uk.com> com>
To: CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com
Sent: Monday, June 18, 2007 4:14:51 AM
Subject: RE: [CAD_CAM_EDM_DRO] Servo Motor & Driver

If the motors and servo drives are good, try to find out some more details

of the servo cards.

They will probably be analogue 0 to 5V, 0 to 10V or +/- 10V signal input.

They will also probably run in velocity mode.

If you can set them to toque mode, then you could use a pixie card to drive

them, simple parallel port IO card and it will run off mach3.

Personally I would keep with the big servo's, and avoid steppers.

Many people work OK with steppers but really they are not ideal for many

reasons in this application, though some of the problems can be overcome.

As to servo's your's are that big you are not easily going to find a

step/direction drive card, there presently aren't any 350V servo cards in

the hobby scene, but you could drop the voltage and use them at half speed,

there are a couple of possibilities here, amongst four viable cards, two are

definitely not viable, one has questions one is too new to know at present.

If your motors and cards work keep them, to replace with something as good

is really going to eat cash.

If the servo cards are faulty, try looking at Granite Devices new cards, and

dropping the servo voltage, these might be viable. With the voltage bit,

keeping things simple, the voltage is proportional to the motors maximum

speed, the current proportional to it's torque.

If you want to go the EMC way, then Jon Elson has some viable cards he may

be able to setup to meet your needs.

Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.

Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_ DRO@yahoogroups. com

[mailto:CAD_CAM_EDM_ DRO@yahoogroups. com] On Behalf Of weedytan

Sent: 15 June 2007 16:55

To: CAD_CAM_EDM_ DRO@yahoogroups. com

Subject: [CAD_CAM_EDM_ DRO] Servo Motor & Driver

Hi all,

I was asked by a friend to look at a Taiwan made ACRA Vertical NC Mill

(year 1996 or 1997) today wherein the controller is dead and to find

out the feasibility of converting it to a CNC using Mach3 or EMC. Here

are some details:

1) The servo motor has a name plate that says: Special VR Motor made

by Servo Products Co., Pasadena; Voltage - 350VDC; Torque - 115 in-lb

(continuous) ; Current - 6 amp/phase; 3 phase; 3.2 Ohms/phase; 400 RPM

2) The servo driver board says ZD-6363 Rev I.

3) This is a 3-axis NC mill with 3 HP Induction Motor for the spindle

controlled by a VFD.

4) It wasn't in use for about 2 years and it boot up Windows 98. After

which, it will not go into the software controller.

Since I am more used to Stepper Motors/Drivers, and totally ignorant

of Servo Motors, may I ask for some assistance for the following:

1) How can I test without going thru the controller if the servo

motors and/or servo drivers are still alive?

2) If the servo drivers are dead (most likely, as someone previously

worked on it and gave up), what alternative servo driver can I use?

3) Is it advisable to use stepper motors/drivers to replace the servo

motors/drivers in the same holding torque range? If not, and if I need

to replace the servo motors as well, what newer model of servo motors

and drivers can I use? Take note that the servo motor has a continuous

torque of 115 in-lb (about 13 Nm or 1,840 oz-in).

TIA for whatever info you can provide.

WT

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