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Lincoln Welder Voltage Erratic

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It is on my list of things to do today, to check on the capacitor values. I built the thing to be as compact as possible. That, and using what I could get. There are two cabinets back to back. So I have to remove the unit from against the wall to get at the back cabinet, where the capacitors are. I had a plate, laser cut (circles) that the capacitors fit into and are siliconed into place. (It's nice to have friends with CNC lasers!) That way, if the caps ever blow up or leak, they don't make a huge mess all over the other equipment. I took readings on all of them and made labels, but never recorded them!

As far as the voltage goes, I could run it on 230 volt, BUT I still need the transformer, because the MOTOR is 600 Volts. It was a freebie! And so was the transformer. So I make the artificial phase at 115/230 and step it up.

I did buy surplus overload relays that I was intending to install for protection, but you guessed it, I never got around to it! lol

One thing I never got right either. I had a current sensing relay that was supposed to switch in the contactor for the starting caps, but that proved to be extremely load sensitive. For the time being, I just do it manually, but thought I would install a timer. Suggestions on this would be appreciated too.

Thanks.
 
600 Volt motor? Thats makes this far more interesting. ;)
All of my formulas and circuits are based on the standard 230 volt three phase motor systems. Although I have done two 480 volt converters so far and they worked out well. :)

I do need some additional information first.
What is the input amp rating of the welder and the motor?
How may leads are coming out of the motor?
What is the KVA rating of the transformer and is it a delta or Wye connection on the primary and secondary connections?

If the motor phase balancing capacitors are on the 600 volt lines the capacitor values will be much smaller.
Given a 2.6 :1 voltage step up the capacitor values will only need to be around 100 - 150 uf.
I will have to do some recalculations and what not first.
I will work up a basic schematic tonight and try to come up with some realistic values for the components needed based on what numbers you can give me. :)
 
Thanks!

For starters, the phase is manufactured at 230 Volt!Then put into the transfromer, stepped up to 600 volt, conennected to the motor and also this is where we take our power. I guess one could take power off the primary for 230 3 phase just as well.

Now, I won't talk about starting capacitor values as that seems to work fine. But they are around 1500 mfd.

But, I can tell you now after having looked, that there is one 40 mfd capacitor (at 370 volt rating) from one leg of the 230 volt to the artificial phase and a capacitance of 161 mfd (at 440 volt rating) from the other leg of the 230 to the artificial phase.

I did not compute any of these values for that is far above my head. They were given to me, but I'm not sure how qualified the person was.

I will get that other data for you.
 
O.K. The Lincoln CV 250 (Constant Voltage) nameplate indicates that for a 575 volt connection, the welder draws 14.3 amps at 250 amps output and 11.3 amps at 200 amps output.

The motor is a ten horsepower Westinghouse "Life Line A" type. Probably rather old. The nameplate states 550 Volt, 10.4 amps and 1745 RPM. It has three leads coming from the motor.

The transformer is a REX Manufacturing, Y configuration rated at 12 KVA.
230Y, 600Y


I do still have a Ferranti Packard Current transformer on one of the incoming 230 volt legs. It was used to try and build my current sensing starting system. This is the type of transformer that is used for hydro metering applications. I believe it was good for 200 amps or so and figured it would introduce only a little resistance to the line. But I guess it does introduce a little inductance. Perhaps, I should short it out of circuit!

Thanks again.
 
Sorry for the long delay but today I was rained out and finished the phase converter schematic. This should cover your system.

You will need to add power factor correction capacitors between the step up transformer and the motor. The values are included in the schematic also.

I did a small test using three single phase transformers and a 3 hp motor set up for 480 volt.
I used the standard circuit as shown below and just put the transformers in series with what is shown as the motor leads in the attached schematic.
All if the start and run functions seem to work just fine with the transformer in the middle between them and the motor.
This should allow you to set up the welder to run at 240 volt input while the rotary converter motor runs at 600 volts. Plus this eliminates the transformer from having to carry the full welder load too.
 

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Thanks so much. But I have some more questions. I would have preffered running the welder on 600 as I can run a line to another building whereas at 240 the conductor size would have to be bigger, but aside from that.

Don't C1 and C2 go to L1 and L2 and not both to L2?

And, I thought these capacitors would be of different values, not that I have the brains to know exactly why!

Are the power factor capacitors used in addition to the caps that make the third phase? So three additional caps accross the three phase?

Are calculations for capacitor values done based on idler motor hp or the load hp?

Lastly, any suggestions if such a phase converter should be used for several different loads. Milling m/c, grinder AND welder???

Thanks
 
Sorry about that. I fixed the schematic.

For proper phase balancing both C1 and C2 always need to be equal. When they are not is when you get the inefficient phase conversion that has poor voltage and phase angle stability. (standard phase converter design)

You would normally just size the C1 and C2 values to meet the requirements of both the motor hp and load KW requirements on a dedicated use application.
For example if your motor is 10 hp and running at 600 volts it would need approximately 40 uf for each C1 and C2.
If your welder uses 10 KW you would add another 30 uf for C1 and C2.
That would give you a total of 70 uf for each C1 and C2.
That number is not set in stone and if all you had was a 60 uf or an 80 uf it would still tolerate it without much fuss.

The capacitor values are to be calculated for running load. Having too much at no load is better than having to little while at load.

For multiple loads it works best to set up the phase converter to have the right capacitor values for itself and then have each device have its own capacitors located with it and only are part of the circuit when the device is in operation. That way the system stays tuned properly for each device and will also stay tuned if different devices are being run at the same time.

Small loads that are under half of the phase converters motor rating typically wont need any additional capacitors. The system is actually very for giving to having small loads attached.
You most likely will only need to have the additional power factor correction capacitors for the welder or for motor loads greater than 5 hp.

All the capacitor values are based on hands on development I have done over the years and found to be the most efficient and adaptable to different working conditions. I have found that with a few odd motors and unusual load conditions there are times when the capacitor values can be reduced to as little as 60% of typical.

So you may want to take that into consideration. your application is different than anything I have personally built before.

I am curious to see how this turns out!
 
When considering voltages, is working on the 110/220 side considered 110 for capacitor values?

I am curious how the values for C1 and C2 would be the same. I would have thought they would be different. In fact, I can't really begin to understand how the frequency and three phases created in an RPC compare to real three phase power. After all, I am not making three phase power out of two phase, I am making it out of single phase power.

I visited my local motor shop and was quite discouraged. For one thing I had forgotten how much money I had spent on the relatively few caps I had purchased. A 100 mfd at 370 Volt is sixty five bucks! What was worse, I wanted to buy caps to put on the welder, but 400 volts is as high as anything they have in their books! I would just hate to think of the price!

I will have to source surplus caps, but unfortunately that always takes time and more effort. But will I even find ones for 600 volt?????

But I definitely want to stick with 600 volts for the welder. As I mentioned it lends itself well to long runs and besides, neat (cheap) equipment is always becoming available for 600 three phase, because so few can run it at home!
 
All values are considered to be for 240 volt systems. So the start capacitors should be 250 volt rated units.

I never buy capacitors from motor shops they stick you every time!

Check out eBay seller G&G machinery. I have bought capacitors from them many times. I typically buy lots of 10 at a time in the 100 uf 370 volt size.
Right now they are $135 for ten with free shipping. They also have the motor start capacitors too.

I have a few buckets of 660 VAC 12 uf power factor correction capacitors.
I did some on line searching and they seem to sell for around $45 a piece.
I would happily sell you mine for $5 each, you pay shipping. I have 20 - 30 good take offs. I am doing shop clean out this week and would not feel to bad if they went some place and made themselves useful.
They were on 480 volt UPS power units from the mines. So I doubt they got much actual use.

Its hard to explain how your getting three phase from single phase exactly but basically all the motor does is use its rotor to make a 120 degree phase shift between the three windings.
Each winding is acting like part of a transformer of sorts but it is doing phase angle shift not voltage change. The capacitors act like an LC tank circuit on each of the phases. Thats why they need to be fairly specific to what size motor and load they are running.
the motor windings and the capacitors try to oscillate at 60 Hz and the rotating motor rotor works like a generator to carry the power from the single phase winding to the other two windings while keeping them at 120 degrees phase angles from each other.

When the capacitor values are in the right tune with the motor and load they are creating a true three phase output.
 
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