Review Update: Delta 16" VS Lathe - PM/Jet VFD Info (long)

[Troy]

interesting, thanks for the links.

Troy

Taunt wrote:

[DG]

As an update, couldn't find the old DIY interface card, so I drug out the old IC data books and cobbled up a new one. Far fewer parts this time around, due to the more modern ASIC's available. Gotta love that misc. semiconductor junkbox that the ex-SWMBO wanted me to toss.

took far longer to find the almost forgotten prototype stuff than to build the RS232/RS485 interface. Granted, it's not destined for retail distribution, but it satisfied my curiosity as to what's going on in the controller. At least I now have a dump of the internal register settings - few of which differ from the factory defaults.

Suddenly, a CNC lathe for turning segmented vessels is sounding like an interesting (and complex) project. One hand turned original, and a limited production run of signed, machine turned copies. That CNC hollowing rig is sure to be a bear to design.

These damned evil computers are now invading the woodshop... Is there no escape?!

FWIW

[DG]

Almost indispensable for digital work. Problem then becomes keeping up with the constant need to upgrade to ever increasing sample rates.

Everything has become so intricate and specialized, it seems there is little room for generalists these days - particularly those with low thresholds for boredom, a desire for breadth, and an inherent mistrust of all blustering authority.

FWIW

[Frank Boettcher]

It has been my experience that they actually give you what they are capable of and hope that you will accept it. You might be surprised at how "tolerant" companies become if it is a choice of having something to sell or not. If you think that chinese iron foundries have process capabilities that are even close to the best or even worst U.S. foundries you are kidding yourself.

I think the trend toward not allowing the end user to have the choice to be discriminating for 10-15% more is a bad thing. That is where we are heading and we are almost there.

Frank

I represent no one but myself.

[DG]

The original post discusses problems with runaway motor speed and failure to remove motor drive when the stop button is pressed. Additional info as follows.

These findings are applicable to all AC motor/VFD setups. Additionally, I am now able to reproduce the fault at will.

The process of exploration reveals that the motor rotor is a rich source of EMF which is induced by the harmonic rich pulses from the VFD Drive. It seems to be aggravated by the 10kHz carrier rate chosen. Imagine my surprise when I discovered that there is up to 45 volts of crap present on the rotor, and current up to .5 amps. The unpowered-state resistance of the rotor to ground varies from 0 to 125 ohms. I would hazard a guess that bearing erosion or fluting is a potential problem since the only path to ground for this potential lies in the bearings themselves. A prudent consideration on any VFD setup that does not use a specialty motor would be some sort of rotor grounding mechanism. A graphite tipped grounding strap which rides on the end of the rotor shaft, for instance; similar to almost every VCR head drum motor ever built.

But this is not the only source of my immediate problem, however. Apparently, the controller is working as advertised, but excessive regeneration is causing the controller to hang in an infinite state of overvolt protection while waiting for the DC Bus voltage to subside before decelerating the motor. The feedback from the freewheeling motor never subsides, so the controller just sits and waits. How do you reduce regeneration? Well, one way is to apply a load - and sure enough, placing heavy pressure on the handwheel causes the controller to respond and continue on to decelerate the motor.

So, what is the cure? That's a tougher question, since any meaningful changes would probably require rewriting register settings in the controller and/or the addition of a zero phase reactor and/or shielded motor feed wiring - which would most likely nullify their picky-ass warranty. But since any number of replacement controllers are probably going to respond in the same way, the fix is probably not as straightforward as replacing a defective part. So we end up in a Catch-22 situation that has probably resulted in loads of these lathes being shipped back as terminally defective. And I'll be darned if I'm waiting until January of next year for a part that probably won't fix anything, or paying for the modifications out of pocket. I've got at least two hours in the project already - not counting the interface and VFD familiarization.

The thing that gets me, however, is that I bought a lathe to turn wood, not to troubleshoot in lieu of the seemingly dysfunctional R&D team at Block and Wrecker, or to sit for 3 months+ waiting on a fix. This could get ugly... ;-)

[The Visitor]

Could that (feedback) be the real problem I had with my controller?

I had to extend the deceleration time so it would work properly. Otherwise it would trip off and the lathe would coast to a stop rather than elecytrically brake. The error signal I got was somthing like "line voltage problem" and when I asked at delta they said I have a main power problem. Somewhere, I think the book, gave me the idea to adjust the de-acceleration pot. It never happens with slightly less electric braking. It is extended maybe 3 or 4 seconds.

John

[DG]

Your controller sounds like the old Baldor unit. And from what I understand, many had problems with it going into FAULT mode a lot.

The Delta.tw unit is totally digital and contains no potentiometers. The accel/decel rates are set by writing to EEPROM registers through an RS485 port. There are two groups of registers for fast and slow, selectable by switch. However, mine is already set to slow.

But the problem is that it WON'T shut off the motor. I'd prefer a coast down condition over a won't stop running situation any day.

nonsensical ramblings... I do note that they have the Braking Resistor Threshold set at 380v but the Over Volt Stall Threshold set to 370v. Normally the OVST would be set a little higher than the BRT. The AVR is turned off during decel as well. All three of these are potential suspects.

I'm guessing that if the BRT were set to 370 and the OVST were set to

380, all would be good in the universe as concerns the failure to shutdown motor drive.

FWIW

[R. Pierce Butler]

DGG wrote in news:f6kfi2pf83lgrf4qsd6k47fvblk5q2ls2v@

4ax.com:

So who makes the VFD for Delta/Jet et. al.?

[DG]

As mentioned WAAYY up this thread, it is Delta Electronics of Taiwan. No relation to Delta WW. I thought perhaps they were labeling their own until the need revealed that it was an independant Asian company.

An industrial user relates his experience:

--------- I have a lot of experience with Delta drives.

We have a lab set-up where we did the Pepsi challenge with Delta versus other drives. (The tester is a NEMA 4 cabinet with heaters and a variac to raise the line voltage to over 500 vac to simulate NA utility conditions. Externally it has a bonitron unit for braking, marathon blackmax motors, and opposing drives which have torque limiting to provide loads. It's a really interesting set-up needless to say.)

We ran these drives at ~150*F at 520 vac for over a month. We ran them loaded with an 5 sec accel and decel time. All the other drives failed, these ones, we couldn't get to trip or fail.

It was a test to see how well they were made. The research that I found, was that Delta is one of the biggest power supply mfg. in Asia. We felt that if they make great power supplies then their drives would be made just as well.

Inexpensive yes, Cheap no.

The problem with most Asian drives is that they are voltage intolerant on the high end. In Japan for instance, the micro-drives are designed for a 400 volt system. When they go to get UL listed, they have to drop there high end to 460 instead of 480 to meet the requirements. They can still be used with great success if the proper line reactor or bucking transformer is used to stay under 460 +/- 10%.

The Delta's don't have this problem.

I'm not a salesman or rep...I have no real brand loyalty per say. Are there drives out there that can do a better job with more bells and whistles, sure. But I happen to agree with dpc. If they work for you, then use them.

IMHO, Carl

---------

FWIW

[DG]

Well, kudos to Delta/B&D for getting a replacement part shipped well ahead of the computer projected date. Received it yesterday, and I am now finishing up a large 13" Ash and Black Mesquite bowl.

I've been using a small 6" straight rest for bowl interiors on the Jet Mini, and with a certain amount of adjustment, it works fine. But now that I've progressed to larger diameters, it turns out that a straight rest doesn't deal well with deeper bowl bottoms. Bought a Delta

46-404 "French Curl" tool rest, and consider it a bargain at $23. Made in Taiwan, reasonably well finished, although the curves are not quite what I expected. The acutely curved side works OK on interiors, but the other side was probably designed to be used on bowl exteriors, and due to the bulk and design of the rest, the angles are wrong for interior work. And if the bowl were much deeper, it would be less useful. I would have preferred two interior curls, one large, one small, as I still use a straight rest on the exterior, but that's my preference.

FWIW

[George]

They make a sturdy extension if you want to drop the cash. Lots more reach available than most would feel comfortable with, but necessary on my old Delta to reach around a bowl. You're right, though, no need for an "exterior" curve. Straight rest can be brought in easily for average close.

's the rest I have, and I love it.

[DG]

Thanks, that is pretty cool. I like the dual mounting hole idea.

Knew about the Sorby rests, but their 9" bowl rest is also too small. Works fine on a Jet 1016 Mini, but it's a toy on this larger lathe.

Bought the "French Curl" rest because it was local, cheap, and there was a bowl on the lathe I couldn't seem to finish without. But it was still a bit shy reaching the bottom.

It's one of those maddening things that makes you want to take up blacksmithing. Another is the tool rest base. The blasted rough-ass casting is so tall, that it won't even clear a 12" bowl on a 16" swing lathe, and is one of the most recalcitrant things I've used. I'm working on a fix for the "takes two hands to move it" problem.

Now with some steel, a welder, lathe, boring setup, and some time...

[Bill]

worthwhile but I already have a spare shaft (25mm).

Bill

[George]

Tough question to ask a non-machinist. Measures 3/4" diameter (shanked from

1") and there appear to be 6 full threads in the 3/4" depth. Imagine that would be something standard?

[George]

Follow my own. A regular 3/4 coarse off the tractor threads right up.