Yet another Buck Boost Newb (Help me lower my 240v to 220)

Good evening all,

Seems like every time I try to go out and learn how to program my old yasnac lathes I run into problems running the machines. Latest problem is spindle drive randomly turns on and off.

Best guess so far is my incoming voltage is around 245+ phase to phase. (Running on a 30 HP american rotary converter).

What I'd like to do drop my voltage levels down around 220 if I can. I betcha that will make some of the mysteries I've been chasing go away.

Seems like i've got two options. 2 buck/boost transformers at each machine (6 total) or I can put 1 single phase transformer on the input to the rotary converter. I'm running that converter on 100 Amp breaker.

I get pretty confused looking at transformers though. Can someone enlighten me one what would work for what I want? Seems like there are lots of options. Is any 240v transformer going to do what I want? I'd love to buy one on the cheap/used etc, but I don't really want to go through iterations of ones that didn't fit the application. Been looking on craigslist, but not exactly sure what i need to be looking for.

Any suggestions?

Thanks in advance,
Joel

Case in point. Will this work? Sure seems big enough. But can I buck with it to suit my needs? Primary seems to take the right input, but the Secondary doesn't look like it will give me what I want. Out of my depth.

Acme Transformer

Acme Electric Corporation - T2535163S - 12/24 Sec. V - Four Windings, 1-Phase 1.KVA 6 Hz , 24x48 Pri. V 1-Phase - Allied Electronics

wolfenstien said:

Good evening all,

Seems like every time I try to go out and learn how to program my old yasnac lathes I run into problems running the machines. Latest problem is spindle drive randomly turns on and off.

Best guess so far is my incoming voltage is around 245+ phase to phase. (Running on a 30 HP american rotary converter).

What I'd like to do drop my voltage levels down around 220 if I can. I betcha that will make some of the mysteries I've been chasing go away.

Seems like i've got two options. 2 buck/boost transformers at each machine (6 total) or I can put 1 single phase transformer on the input to the rotary converter. I'm running that converter on 100 Amp breaker.

I get pretty confused looking at transformers though. Can someone enlighten me one what would work for what I want? Seems like there are lots of options. Is any 240v transformer going to do what I want? I'd love to buy one on the cheap/used etc, but I don't really want to go through iterations of ones that didn't fit the application. Been looking on craigslist, but not exactly sure what i need to be looking for.

Any suggestions?

Thanks in advance,
Joel

Click to expand...

"Best guess so far" and a mouthful of wet cigar ashes will probably get you thrown out of Starbucks, no coffee, and no wiser about what is really going on.

A nominal 11% overage above 220 all by itself is not likely to be the prime culprit, and may not even be a player.

Dig deeper, ascertain what IS, before buying transformers of any kind.

Monarchist said:

"Best guess so far" and a mouthful of wet cigar ashes will probably get you thrown out of Starbucks, no coffee, and no wiser about what is really going on.

A nominal 11% overage above 220 all by itself is not likely to be the prime culprit, and may not even be a player.

Dig deeper, ascertain what IS, before buying transformers of any kind.

Click to expand...

Any directions you would particularly suggest? Fuses on Spindle Drive all check out. This is the only alarm I'm getting. I've got a second phase converter down below. Maybe I should run a cord out to that one and see what I get. Heck Its a 100+ ft away should get a couple volt drop out of that anyway.

wolfenstien said:

Any directions you would particularly suggest? Fuses on Spindle Drive all check out. This is the only alarm I'm getting. I've got a second phase converter down below. Maybe I should run a cord out to that one and see what I get. Heck Its a 100+ ft away should get a couple volt drop out of that anyway.

Click to expand...

A dual or quad-trace Oscilloscope is lighter even than the power cord. I haven't been without at least a single-trace since I was about 12 years old.

Dunno about you, but power hides lot of s**t, CNC are computerish critters, and I can't 'see' electricity and its various stealthy events worth a damn with the naked eye, nor even a good, but simple-minded meter.

If that sort of gear is not on your dance-card, call in someone who can save weeks of guesswork in just a few minutes with relevant CNC experience and the clever use of decent test equipment.

"Best guess so far" should be left out in the carpark.
Wastes YOUR time, and OUR patience.

Well, you think it is an overvoltage. maybe so, maybe not

What does the machine spec say it wants for voltage?

Do you get any error message that says what the issue is when it shuts off? ( I know nothing about the machine you mentioned, so the question may be off the wall) If it is an overvoltage, you might get an "OV" or some such thing. Many drives will give you the last 4 (or more) trips in a "history" that is accessible through the keyboard.

I definitely agree that throwing money at the problem unless you have some idea what it really is may not be particularly useful. Might be something totally different, inside or outside the machine.

With 220V, the normal variation that has to be allowed for is up to +10%. That would be 242AC, and 245V would be over that. In that case, you could be correct.

If the machine takes 230V, then +10% is 253 VAC, and 245 is within limits. And for 240, the thing should accept up to 264VAC.

Now, I know that some machines have really stupid specs, especially older CNC. So maybe it wants 220VAC, and they really mean it, no +10% allowed. I have seen that called for, although usually it isn't QUITE that strict, no matter what they say.

If you have a real problem, that is messing up production, and the machine specs are of the "220V and not a volt more" type, it may pay to get some buck boost units and put them in to see if it fixes things, because if it does, you are back in business. No sense over-analyzing.

So... your options.... If you get transformers that have a secondary rating of the current you need, that are 240V to 16/32 V, you should be able to get the volts knocked down. These will be single phase transformers that each handle one phase. You will only need two. Wires are labeled X1 to X4, and H1 to H4, usually.

OK, for a 32V reduction (approximately), Using a transformer with 120/240 primary (230/460 primary is slightly different wiring)

On the transformer, connect X2 to X3, connect X4 to H1, Connect H2 to H3.

Now, connect one transformer from phase 1 to phase 2, with (for instance) H4 on phase 2 and X1 on phase 1. Take the new phase 1 output off of the junction of X4 and H1.

Likewise, connect the second transformer from phase 2 to phase 3, with H4 on phase 2 and X1 on phase 3. Take the new phase 3 output from the junction of X4 and H1 as before. Phase 2 goes on through.

That will drop your voltage from 245 to 216, a bit under the 220VAC you want.

For 16V reduction:

If you want more than that 216V, then instead of connecting X2 to X3, connect X3 to X4, and X1 to X2. Input to X1/X2 and H4, Output from the connection of X3/X4/H1. Connect to 3 phase as before. That will give you about 230VAC, somewhat over your goal, but much better than 245VAC..

There are also 240V to 12V/24V types, that would be able to get closer to 220V using the 24V connection. I don't see them as much.

For sizing the transformers, you need to know what the machine full load current is. Or the sum of all the machines you want to connect.

Then, the buck transformer you use needs to be rated for that current AT LEAST, in the connection you will use. There will be a current rating for the 16V and another for the 32V connection,( which will be half the 16V current). Make sure the transformer is rated for at least the current you need at the proper voltage reduction. Better it should be rated for maybe 25% to 50% more.

Here is an on-line calculator, if you prefer to go that way

Buck and Boost Transformer Calculator - Schneider Electric United States

Before you start looking for transformers you need to find out the machine specs, as others have stated. In my experience most older Japanese designed machines are designed to run on 200V +/- 10%. If this is what you have 220V would be on the high end of the spec. If you have multiples, you need the data for each one, they may be different from each other.

A transformer before the RPC might seem better, but could be worse if your machine requirements are different. It can also affect the balance of the RPC output by changing the input voltage.

Do the homework first on what each of the the actual machine load requirements are voltage and KVA requirements before you start looking at transformers. You may find that you have differing requirements that one transformer will not accommodate.

Anything before that is a shot in the dark.

SAF Ω