VFD Conversion/Overhaul ?

[Verboten]

Hello,
I have an old Allen Bradley 3 phase VFD (1334-EOB from 1987)
Input: 460 V , 13 A, 10.3 kva , 50/60 Hz
Output: 0-460 V , 15 A, 10.3 kva, 0-60 Hz

Looking at the parts mounted on the large heatsink toward the back of the unit - the input power is rectified and then fed into a + and a - buss bar that go to 2 large capacitors and 3 power modules (Toshiba MG50M2CK1), each module has what looks like (the component is shrink wrapped) its own smaller capacitor between the + and - buss.

This is the only information that I was able to find on the MG50M2CK1 - if someone can point me to a datasheet it would be helpful ! (I have searched quite a bit).

Description = Darlington Transistor Array
Number of Devices = 2 -------------------This is the number of Darlingtons and not an inventory #, right?
P(D) Max.(W) Power Dissipation = 350
h(FE) Min. Static Current Gain = 100
@I(C) (A) (Test Condition) = 25
@V(CE) (V) (Test Condition) = 5.0k

The modules have 5 terminals. The outermost terminals are connected to the buss bars. The output power for the motor comes from the center terminal of each module. Two twisted pairs of wires control each of the modules.

Would it be possible to turn the drive (mainly the parts that I described) into a single phase to 3 phase 230 V power supply? It wouldn't have to be variable frequency - getting 3 phase at 60 Hz would be enough to start.

Pictures of a 1334-EOB on ebay :http://cgi.ebay.com/Allen-Bradley-Ad...QQcmdZViewItem

Mine is similar except for not having its own enclosure and different small "function expander" card.

Picture of a MG50M2CK1 on ebay (no schematic or further info) :http://cgi.ebay.com/TOSHIBA-MG50M2CK...QQcmdZViewItem

I have built a basic rotary phase converter before and have no real application in mind for this device at the moment other than testing some small motors and learning something new.

Any suggested ICs? Links to information? Any input, ideas or suggestions will be appreciated.
Thanks,
-Jason

[Al_The_Man]

The parts you describe would probabally need no conversion, IOW they should work at 240vac, you would need to find out how the low voltage is produced, usually through a switching supply to get the low voltage for the control logic etc. You could even hook it up to 240 1 phase and see if the logic and display come on as some switching supplies will operate over a wide range of voltages.
The Fan is usually fed from low voltage so check the voltage on that.
Al.

[Verboten]

Al - thanks for the reply,

The 3 phase input is color coded Red, Brown, and Black.

The black branches to a KTK-1 fuse (I assume 1 means 1 Amp) and becomes a Green (I don't know why, maybe they didn't have that many wire colors, but it does). The Green and Brown then go to a control transformer that has 4 outputs (8 wires). The Red as far as I can tell goes directly to the 3 phase rectifier. I think that I can see part of the logic power supply on the power board - I'm not sure if it is a switching supply (from the discussions that I've read and viewing other power supplies - it also looks like they got a good deal on the same size capacitor).

Unfortunately there is no fan or terminals for one inside of the drive, I think that an external fan was used to blow through the channel at the back of the drive.

So, If I were to connect the 230 1ph to the Brown and Black and the logic was under voltage that would not cause a problem (if all is well) - it would just not power up, right? If that was the case after trying that could I place another control transformer before the one on the drive to increase (I'm assuming double) the Voltage at that point? - I just double checked the colors of the wires entering the control transformer and noticed that it appears to have another input available, hopefully the one that I would need (I believe that I can check this pretty easily with my multimeter) , but would the extra transformer idea work just in case?

I guess that it would be nice to see if the drive works before I rip it apart (carefully disassemble).

But if all that does not work and I had to (for the sake of a hobby project) control the modules or similar ones that I already have (I think they are IGBT Half bridges) by another method could I use an IR2130 3-Phase Bridge Driver or similar (if there are any)?

http://www.irf.com/product-info/data...ata/ir2130.pdf

Here is a Design Tip pdf from IR for a "3-Phase Bridge Drive With Overcurrent Protection" using the IR2130

http://www.irf.com/technical-info/designtp/dt94-11.pdf

I don't know what type of logic signals it wants for Hin 1-3 or Lin 1-3 but it looks simple and interesting to me. Any ideas on this? Would there be a better/simpler method?

Thanks again,
-Jason

[Al_The_Man]

I would say you have two possibilities there, either, as you say provide another transformer for the present control txfmr, or fire it up and see what the voltage is from green and brown to the third wire, if it is 50% of the voltage to the other two then it may be a 240v connection.
Al.

[Verboten]

Thanks again Al,

I connected the 240 (I could have sworn the last time I measured it - a while ago - that it was closer to 230) with no result other than finding out that I can't just change the connections on the control transformer to make its output even close to double. On the bright side there was no smoke or fire or even blown fuses!
I will look to see if I can find a small transformer to step up the voltage and try again.

If I hit the jackpot and the drive works right away that would be great! (I would have to sell it and move on to something that I could tinker with ) I would think that the chances of that (fingers crossed) are slim - it is 20 years old with maybe a more than a few dozen of what I imagine are "obsolete" ICs, hundreds of discreet components, and I've noticed a few pieces that are cast into plastic black boxes. If any one of these components were damaged it would probably be impossible for me to trouble shoot it during this lifetime with my limited knowledge. Looking at the AB site and their "Legacy Products" manuals (every one you could hope for except how to set up the drive -I'm perhaps a little bitter about that) it seems like they were trying to make the swiss army knife of motor drives with an add-on that you had to buy for everything along with a tome of a manual just to hook it up, nevermind understand it.

Perhaps another question would be: How difficult, expesive, or time consuming would it be to make a homemade IGBT based phase converter? The igbt modules are not that expensive to get surplus if you are not looking for specific drop-in replacements (the ebay link that I posted to the ones that I have is waiting for a eureka moment), they seem to be in lots of obsolete drives. Why would this be any harder than making your own stepper or servo drive and software? - or even balancing the phases on a rotary phase converter? There seem to be ICs available to greatly simplify the process from what it was 20 years ago (just like for steppers and servos). What are some of the pitfalls that I am not seeing?

Thanks,
-Jason

[HillBilly]

Here is a data sheet.

Darek

[Al_The_Man]

Originally Posted by Verboten Perhaps another question would be: How difficult, expesive, or time consuming would it be to make a homemade IGBT based phase converter? -Jason

Unless you are a sucker for a challenge, I would not even bother, looking at the prices you can get them for on Ebay.
Modern Flux Vector drives have processors that will take a snap shot of the motor characteristics and use this to process electrical feedback for accurate vector control without using tachs, encoders etc.
You MAY save some money, but certainly not time by building.
Up to the variable frequency controller stage should be fairly straight forward using IR application notes.
Al.

[Verboten]

HillBilly- Thanks for your help with the datasheet, I appreciate it.

Al - I do enjoy a bit of a challenge as long as I am not getting in too far over my head. I of course do not want to waste too much time trying to something that will be impossible or done much easier in a different way, but I am probably more than a bit addicted to the "I built that" moment.

What I was envisioning was not just a drive for a single motor but more of a shop power supply that would supply (240 V, 60 Hz, __A) power to other drives and motors. Wouldn't all of the complex features mentioned prevent or complicate this?

Would such a power supply be more efficient than a shop supply from a rotary phase converter (I could see it being more convenient)?

For interest: This IR pdf explains a bit more about the input signals for their IR2130
http://www.irf.com/technical-info/appnotes/an-985.pdf

Thanks again,
-Jason

[xjack]

I wired ir2130 as DT 94-11 Design Tips
The Problem is when i start the Motor it Runs normal 2 to 3 time
then if i start the motor it strugles to run or runs steped
after changing new IR2130 it runs for one time and again it strugles to run ?

[JRaef]

There are a litany of problems with trying to resurrect an old VFD.

The first and foremost one is that if the VFD has been unpowered for any length of time, i.e. over a year, chances are that the capacitors will be toast shortly after energizing them. If you have a variable transformer you may be able to "reform" them by slowly increasing the voltage over a period of hours, but even then it may not work if the electrolyte has already dried out. On top of that, the generally accepted lifespan of a capacitor is 5-7 years. Yours are 20 years old! Once the caps are gone, the replacements would be more expensive than buying a new drive.

Problem #2 is the fact that all of the little caps on the PC boards are also old and likely to fail.

Problem #3 is that in most cases, a 480V drive cannot accept 240V 1 phase as an input, it will likely trip off on Low Voltage and/or Phase Loss even if you manage to get it to energize. In 1987 I doubt that AB even bothered giving you an option of disabling the LV/PL protection as some mfrs do now, because they never considered the possibility of using it as a phase converter, especially on a 480V drive. Most of ABs current drives will not allow you to do that.

The last problem I can think of is the Darlingtons. They are not likely made any longer, so if you manage to find some, they will be very very expensive.

Then there is a problem with what you want to do in general. A VFD does not make for a good 3 phase converter for powering a facility. The act of switching a motor on on the downstream side of the drive puts a tremendous strain on the transistors, what is called a di/dt surge (di/dt stands for delta-current over delta-time). Each time you do it, even if the transistors survive, you are doing incremental damage to the silicon substrates. In essence you are chipping away at their life span and it usually takes only a matter of months for them to fail, if not sooner. If you want to produce a 3 phase system for distribution throughout a shop, use a rotary phase converter. If you want 1 converter for 1 motor, use a VFD.

[petek]

when your done screwing around with the drive I would be interested in the transister array. My old fugi spindle drive blew up on my shizuoka to day.
Pete