3 phase converter using a transformer?

There is no way to use JUST a transformer to convert from single-phase to 3-phase. If there was, nobody would make rotary converters. There IS a device to convert 90 degree TWO-phase power to three-phase. It is called a Scott Tee, and requires two transformers. One is a 1:1 with center tap transformer, which is easy to set up with most step-down transformers. The other is an 86:100 (I think) transformer, which you pretty much have to make custom. But, anyway, who has 90 degree two-phase power? I tried to design a 90 degree phase shifter with inductors and capacitors. Yes, it is possible in theory, but practically, I couldn't figure out how to do it without drawing insane amounts of reactive current (thousands of amps), or using at least a hundred caps and inductors.

I think where this may have come from is some people wind up with

Jon

I have built several, for special purposes. Most were not as good as a commercial VFD, but served for the special purpose they were needed for (like higher than

It allows you to soft-start the motor, for instance. When starting a

Jon

Much of the above is WELL covered in the literature, or fairly easy to figure out. The stuff that remains a good bit of black magic is the circuit layout. I have done a number of power circuits, and the inductance of the loops of circuit traces is a constant problem. A recent design (in this case a DC servo amp) had what appeared to be pretty well minimized loop areas for the power traces. But, when I got it up to 20 A, the di/dt working on those traces caused a voltage shift at the driver chip that made it think it was supposed to turn the high and low side transistors on at the same time! Boom! I also had a HELL of a problem with trapping an undershoot of the output terminal voltage when the high-side transistor shut off. When the voltage at the high-side transistor's source went below 7 V, it popped the driver chip. I had to add a massive ultrafast diode to ground to trap that undershoot. More ordinary diodes simply would not start conducting quickly enough to keep that from happening. And, of course, these things happen only once per chip, so you need a digital storage scope and trigger it on the right event to capture the situation.

This is where it really gets hairy, and you need the experience in these situations to measure and find the problem without blowing up too many chips and boards. One inch of 3/8" wide circuit trace with a di/dt of 20 A/40 ns (500 million Volts/second) can develop 20 V or so, which will disrupt a 5 V circuit or the gate of a FET or IGBT.

Jon

Thanks Jon, that was interesting. I will also do something to prevent undershoot on my inverter, as well.

According to Ignoramus29795 :

Ig,

While I've found a thread with you participating, I thought that I should point out to you something which may be of interest to you on eBay.

I don't remember exactly which set of dies you got with your hydraulic crimper, but I've found two batches of terminals within its range on eBay, plus one at the bottom of the next size up.

I'll list them in order of size:

2) Auction #5835651129 -- #2 wire (also red) with 1/4" ring holes (20 terminals per lot.)

All are the same vendor, so you may wish to contact him to ask whether he will be putting out any in the size you need. (What does your die set fit? Color and/or gauge -- the latter is needed if you happen to have red, as it could be either #8 or #2.

I've never dealt with him, but the prices seem reasonable, and he has multiple lots in each size. (All buy-it-nows, not true auctions.)

Good Luck, DoN.

Thanks. I have #6 die. I bought a few connectors for #6 wire. I have some immediate use for them for my new phase converter. Right now, I use a terminal block with set screws, but it is a little too wimpy for these wires. I will redo it soon.

I do not think that my crimper is capable of handling 1/0 wires.

O.K. That would be blue insulation on the terminals. But -- you should be able to get dies for both red sizes and the yellow (#4) to fit your crimp head.

Nope -- I just mentioned that one as being part of what he was selling. I thought that I had mentioned that it was too big for you, but apparently not.

Enjoy, DoN.

That's right.

By red, do you mean 1 and 2 gauge? That would be just great.

I appreciate the tip, DoN. I like this crimper and will soon put it to work. So, what sizes do you think it could do? (insulated or non insulated)

Thank you very much.

I mean 2 and 8 gauge. 1 is the same as 1/0, and requires the next size head to handle it. (And that one requires a separate hydraulic pump connected by a hose. An Enerpac will work nicely, if you want manual to keep it cheaper.)

I only know the dies for the insulated style, and here are the sizes:

#8 Red

#6 Blue

#4 Yellow

#2 Red

For 1/0 through 4/0 the cycle repeats on the larger head (which you don't have) as:

I have all of these in my own set except for the 4/0. There are two styles of dies -- one (my preference) for the P.I.D.G. terminals, and the other does not crimp the insulation retention sleeve, just the wire connection. I think (without going downstairs) that style is called "Termi-Grip".

Enjoy, DoN.

Thanks Don. I will keep looking for dies. My current one though, is only good for 6 ga, right?

I saw this die:

Item number: 7511949941

Would it fit my AMP crimper? Is there a document (yes, I looked) that describes these dies etc?

thanks!

That is correct.

Nope. That is for a ratchet handle type, and for much smaller gauges.

You need to pull the dies from yours to see what they look like separate from the crimper. The fixed die (in the swivel part of the head) is secured by a single Allen head setscrew in one of the two faces of the swiveling part of the head.

The moving die is also secured by a single setscrew, but you will have to pump it a few strokes to expose the hole in the ram in which it is tightened. (Be *sure* to screw it back in before you let the ram retract, or you risk scoring the O-ring which seals the ram.)

Yes -- it comes packed with the dies when new. :-)

The dies which I like less come with the following numbers from one data sheet:

IS 1729 (Date 5-13-74

Type: Terminyl & Plasti-grip Gauge Color number ============================== #8 Red 47820 #6 Blue 47821 #4 Yellow 47822 #2 Red 47823

Type: Pre-Insulated & Plasti-grip Gauge Color number ============================== #4 Yellow 47822-1 #2 Red 47823-1

The above dies don't have the necessary part to crimp the insulation-retaining part of the terminal. (Except perhaps the "-1" versions, which I don't have, and which are not shown on the data sheet.)

The ones below *do* have the insulation-retaining crimp parts.

And -- from a different data sheet:

IS 1758 (Date 6-17-74)

Type: Ampli-Bond, Plasti-Grip and Pre-Instulaed AMPOWER Gauge Color number(s) ============================== #8 Red 48752 & 48752-1 MOD.V #6 Blue 47853 & 48753-1 MOD.V #4 Yellow 47854 & 48754-1 MOD.V #2 Red 47855 & 48755-1 MOD.V

With a note for the #2 size: Also used to crimp No 2 Pre-Insulated AMPOWER terminals P/N 325177 and 328942

I could scan them -- but I've got to fix the networking connection between the machine with the scanner (A Windows box) and my unix machines which could make them available on the web. Aside from that, they are all copyrighted -- 1960, 1967, & 1974, so I could not really do that anyway, without permission from the company.

Both are 6-page data sheets, which include details on how to remove and replace the dies (you're supposed to pump it to fully extended before removing.

The side with the colored dot (often hard to see on the Blue ones) should face towards the side with the setscrew.

You could try contacting them. Both sheets have the address:

AMP Incorporated Harrisburg, PA, 17104

AMP is now a part of TYCHO, so I'm not sure whether the old address still works.

Good Luck, DoN.

The original Ronk Add-a-Phase used an autotransformer and capacitors to manufacture three phase.

Thanks Don, I saved your post and will look for other dies. I'll try to also call Tyco at some point.