Messages

201

General Mach Discussion / Re: Replacing a Resolver of an AC Servo with an Encoder

« on: August 28, 2009, 09:56:04 AM »

Well not quite, the drive AND the feedback device. IOW an AC motor with resolver will not run on a  BLDC drive without changing the motor resolver to equivalent hall effect device.
The Fanuc AC Red cap motors I mentioned earlier have a differential encoder and a 4 bit binary code which they use in their systems to produce a pseudo sinusoidal pattern from the 4 bit code, similar to what a resolver would produce.
Jon Elson is selling a unit where he  has found a way to convert this code for BLDC commutation.
I have generally changed the whole encoder if I get the right price.
Nosmo.

202

General Mach Discussion / Re: Replacing a Resolver of an AC Servo with an Encoder

« on: August 28, 2009, 09:13:52 AM »

The BLDC and AC servo's are constructed practically identical, three star connected stator windings with P.M. rotor, the difference comes in the commutation, Brushless DC switches two windings at any one time, like a brushed motor turned inside out.
The AC is controlled with true three phase, sinusoidal in nature.
The BLDC requires three encoder pulses  or hall effect devices to commutate.
 BLDC pattern http://users.tinyworld.co.uk/flecc/4-pole-bldc-motor031102.swf
The AC use resolvers to commutate but some also use the hall effect for initial rotor detection and immediately switch over to encoder resolution pulses to synchronize the  three phases.
Nosmo.

203

General Mach Discussion / Re: Replacing a Resolver of an AC Servo with an Encoder

« on: August 27, 2009, 11:23:26 PM »

Renco are dumping commutation encoders on ebay right now, for $20.00 and $90.00 for the differential bearing model.
Essentially you are converting an AC sinusoidal - resolver motor to BLDC. I have converted a few including the proprietary Fanuc Red caps.
As mentioned, you have to find out the number of pole pairs and align the commutation up when installing.
Renco have the pole pair designation after the resolution, 1000/4 will be for an 8 pole motor.
Nosmo.
 

204

Galil / Re: Mitsubishi HF-SE Ac servos and drives.

« on: August 20, 2009, 10:38:32 AM »

How is that going to work when both drives and Galil are trying to close/control the loop.
For me, Usually the whole idea of using Galil is to use non intelligent analogue drives?
Nosmo.,

205

General Mach Discussion / Re: Lathe spindle brake

« on: August 19, 2009, 09:20:53 PM »

On a VFD that has configurable outputs , I have set one for 'At Zero Speed' this can be used as a software input or switch hardware direct.
Nosmo.

206

General Mach Discussion / Re: Lathe spindle brake

« on: August 19, 2009, 05:39:29 PM »

So it sounds like just braking a normal uncontrolled AC spindle motor. What is the reason for the time delay if the original worked OK?
Nosmo.

207

General Mach Discussion / Re: Lathe spindle brake

« on: August 19, 2009, 04:45:30 PM »

You did not mention what kind of spindle motor/controller it is?
Did it previously brake to a stop, or was it just a holding brake?
If it was a holding brake, there must have been some method or signal to indicate zero speed?
Nosmo.

208

General Mach Discussion / Re: Has anyone used DMM technology AC servo drive or motors?

« on: August 04, 2009, 01:48:23 PM »

They say 20yrs experience, but I have only come across them in the recent few months, they seemed to be aggressively pushing the product on a few sites.
It needs someone to grab one and test it. 
Nosmo

209

General Mach Discussion / Re: TTL 5 volt to 24 Volt for servo input

« on: August 01, 2009, 12:50:54 PM »

The ULN2803 should work OK, I know the ULN2001 has 1us turn on/off time , I have also used the 2N7000 where the signals are just a couple or so.
Nosmo.

210

Galil / Re: Strange #AUTO Galil program behavior

« on: July 22, 2009, 09:08:44 AM »

Did you try TC to see if any thing comes up?
N.