On Monday 07 March 2016 10:04:35 Danny Miller wrote: > I used an Advantech ADAM as an isolated RS232/RS485 converter. It's > rated for high baud rates. > > Like I say, I couldn't find a ground on the X200 that I was supposed > to use, not by the manual. The VFD's input does NOT use optos. IIRC > I even took apart the VFD, found the internal interface IC, located > its ground, and tried to find continuity to one of the input pins- no > dice, as I recall. > > The X200/WJ200, I know they have a target freq and a "target freq > locked" bit. But the live actual freq during spin-up, no, I don't > know of that being available from a reg. > > Danny [...]
Thanks Danny. Speaking as a C.E.T., which I am: In that event, it could be advantagious to know the rail voltages expected of that interface chip, place a 1/1 divider R to develop a bias voltage that would be applied downstream of some coupling capacitors thru resistors to cause them to sag toward a balanced condition when at rest. That would be best described as a Rube Goldberg setup, but it might work. Dependent on the noise levels. However, I would think that someplace on this devices interface, there has to be a common point. From your previous descriptions its apparent that it sits at stopped with all its h-bridges or whatever they call them, on but sitting at an exact 50% duty cycle so the net torque is zero. I think I would scope every interface terminal, in or out, to confirm that this is the source of the noise. And if it has some time on it already, there may be internal bypassing capacitors that have failed with age. I'd automatically suspect ANYTHING with a label rating under 150 volts, inspecting all of them in a power off for a long time condition, with a meter that measures ESR. The best of that type of device is (google for it) the "Capacitor Wizard", a single function device that costs about $200, which can do it incircuit because its signal is too low to turn on any surrounding semiconductors even if they are Schotkey types. For what it does, this meter is amazing, and while I have investigated other dvm's that purport to measure this characteristic of a capacitor, all that I have looked at so far in the nearly 20 years since I bought the Wizard for the tv station where I was the CE in a former life, all failed in some way that reduced their ultimate ability to make a meaningfull measurement. Condem and replace with top quality replacements, any capacitor over a microfarad that measures at more than 2 ohms, and you will have found & replaced even near term future problems. You might, in the process, inadvertantly fix the noise problem if all the capacitors are subjected to the ESR test. I might also comment that the sheckles might be better spent by retiring it, and picking up a suitably rated replacement from ebay that Just Works(TM). You are driving a 3 phase motor which has only 2 ways to be built internally, as an induction motor with very large driving currants at low speeds, or as a stepper motor with a hard magnetized armature that actually runs synchronous to the driving frequency. My bet is on the induction motor, which will not generate a huge voltage across its coils when scoped and turned by hand. A volt or so from any residual armature magnetism remaining, in my experiance usually a few milivolts. A stepper style will generate a coil voltage well above 5 volts in the scenarios I can imagine. But because of its instant stall if pushed beyond its torque ratings, which fade at higher revs, I would never consider using it for a spindle motor. The stall would break the tool, and that gets expen$ive. The induction motors speed will sag, drawing ever more currant from the controller, until the controller sees the overload and sends out the stop signal to the machine as it shuts down the motor, so everything ideally stops in its tracks with no broken tools(mirrors) & none of the "smoke" gets out. And we all know this stuff runs on smoke and mirrors and if the smoke escapes, or a mirror gets broken, it doesn't work anymore. ;-) Sorry, Just Had to throw that in. :) One old farts $0.02, but you may want to adjust that for inflation in the last 81 years. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://makebettercode.com/inteldaal-eval _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
