Electrical help please

it maybe better for him to get self powered welder (Generator combo) or get a 20kVA generator that is diesel operated. Also puts out 3 phase at

230 volts to make it more efficient..

Last time I looked you can get a diesel gen of that type from Harbor freight somewhere around 5k. It's well worth to have in cases that he's running into.

It's more than likely the electric company has too many people on the same transformer, he would benefit greatly if he had his own transformer. The cost shouldn't be that much different, on a business point of view.

That situation sounds like they don't have a lot of generating capacity on the island.

Jamie

I scrapped a reply here bcause there werre too many unkowns. Options with t he power company for one, they could run a dedicated line putting him up th e food chain a bit. Probably not free.

I think you're right about the generator idea, that is unless the power com pany will do it for free. (they will if you are Ford, they did it in Ohio)

But this all made me run the numbers. I found this page :

3/kWh. The national average of electric rates is 0.13/kWh. With diesel at $ 4.00/gallon, a 2080 hour work year, 50 % duty cycle, about four grand a yea r ? Well the power company, with average rates would have been over a third of that anyway, plus the fact that welders make money. Th employer shojld be doubling his money on what the guy makes. So if the guy makes $25 an hou r, the company should be getting $75 an hour. Times 2080 work hours, that f our grand doesn't look so big. Plus there are certain advantages, like he c an work in a pwoer outage. If he is making a profit it is a good thing to k eep working. So really, it might be a good idea. It may be one of those tim es when penny pinching does not pay.

The thing is though is that the power company sells power. They WANT to sel l power. I think they should refeed the guy and give him the aperage he nee ds. However the fact that they came and had a talk with him indicates that thy mght not want to do anyting, especially for free. If noting else they m ight hit him with a peak load meter, which means $0.13/kWWh is probably out the window.

We still need a little bit more info, like what did the power company actua lly SAY. In that area, CAN they asses you for too much load ? Or cut you of f ? That is the main question. If not, they will just have to eat it, so ba sically I wuld buy nothing until I hear about them.

(but thanks for sending me on that hunt, because I thought running generato rs was ALOT less efficient than that)

His power bill for the business is about $200.00 per month. For the kind of money the generator would cost he could buy a new inverter welder that would not have the same high current draw when starting. But right now he can't afford a new inverter welder. I'm not sure if he can force the power company pay for a new xmfr. I'm also not sure that the power company can install a new xmfr and then force him to pay. I do know that in my case, where the voltage is way high, sometimes as high as 260 volts, I was not able to force the power company to lower the voltage and instead I had to install at my cost buck xmfrs so I could run one particular CNC lathe. What about wiring in power factor correcting caps? Eric

Problem with the new transforer idea is it might not work. They might conci evably have to put in miles of lines to get him to the higher voltage lines . this would spread his load out to more of the whole tree. More people wou ld get a voltage drop, but thet drop would not be as severe.

He needs to have a powow with the power company I guess, or maybe not do an ything for now. From what I read you said they approached him ? Need to kno w ore about that. They must have said something. They don't just drop by fo r coffee.

Checking local laws may or may not do any good. There may be none. It may b e that if you want to deal with the power company, you do it on their terms . Some power companies are owned by the municipality, county, who knows. Ot hers are totally private.

One main thing to remember is they want that $200 a month. It is not alot o f money but it is more than many pay. Therefore he should always keep the f act that he CAN buy a diesel generator in his pocket if they try to bully h im for a bunch of money. Another question is - just how much of a PITA woul d it be to move the business ? (I don't mean cross contry here, I mean a fe w miles closer to the power station)

He would move the business if there were a place for it fairly close. We spoke about that last night. There are the main power lines running down the island within 1/4 mile and the xmfr is mounted on a pole acroos the narrow street from his driveway. He would like 3 ohase but the power company wants loads of dough for that option too. Eric

yes, that would reduce them. rotary converters store energy in rotational momentum, and some of that energy will go into serving the start-up.

--
umop apisdn

Today I learned that there is a piece of water called "Useless Bay".

Maybe. It might help the startup, but the rotary converter isn't 100% efficient, so it would add a little energy use on top of what the welder needs.

The rotary converters I know about have to be switched on manually when you want them. This means that if you start welding, and then stop to move the ground clamp or get a new rod or whatever, the rotary converter is still running. It won't draw much power when running with no load, but again, it's more than just the welder itself with no converter. Maybe you can get a rotary converter that can switch itself on and off based on load.

One phase converter vendor I Googled up says that for a welder, you can size the converter as if it was a resistive load. That means an (11,000/746) or 14.7 hp converter. They sell a 15 hp model for $2,360 and a 20 hp for $2,775. Add the freight costs for 200-250 pounds of machine, and sales tax, and IMHO you've made a pretty good dent in the price of a new welder. Cheaper phase converters probably exist.

They should be able to adjust the taps on the big transformer (not the one on the pole - the big one that feeds that one) to increase the voltage a little, but that also means the voltage will be higher when he isn't welding. It also might mean that the voltage is too high all the time for the people that live near the big transformer. They may decline to do it for these reasons, but it's possible.

The tarriffs for electricity should be somewhere either on the power company or state government web site. The bill should say which rate plan or tarriff applies. Usually these are mostly about the price, but there may be something in there about who has to fix power quality problems. Your state Public Utilities Commission (or similar name) may also be able to advice. (This may be different if Washington has deregulated electric power. In that case, an accountant two time zones away makes up whatever rules will generate the most revenue, and changes the rules hourly.)

Looking through a Northern Tool catalog I have, portable gasoline motor- generators rated at 13.5 to 15.0 kW continous seem to go for $3,000 to $4,000 depending on make. There are some cheaper ones if you don't need to support 11 kW all the time.

If your friend already owns an engine, he can buy just the generator head and rig it up himself. You can get ones that run at 3,600 rpm plus or minus, or ones that are designed to run from 540 rpm from a tractor PTO shaft. Bonus: you can unhitch the motor from the tractor and drive the tractor to the fuel, rather than hauling the fuel to a motor-generator. :) That same catalog has a 12 kW PTO generator, which says it needs at least a a 24 hp engine, for $1,500.

If nothing else changes, bad connections would tend to make the welder draw *less* power. But maybe the user is cranking up the welder output power to make up for lower voltage. It might not hurt to at least eyeball how the welder is hooked up to the 240 V AC - is the wire thick enough, are all the connections tight, etc? The fancy way to figure this out is to run the welder for a while and then look at the breaker box / wiring with an infrared camera (like a FLIR). The middle way is to use an infrared thermometer. The cheap way is to (really carefully!) touch the wires to see if they are hot - don't get shocked.

Standard disclaimers apply: I don't get money or other consideration from any companies mentioned.

Matt Roberds

I can build him a phase converter. At least I understand how they work, even though I don't understand a lot about AC. I have built a few rotary phase converters and they all work properly. I was wondering just how much energy would be stored in the motor and if it would have a significant effect on the current surge. I also know about the high voltage thing. Since I am near the beginning of a long run the voltage at my shop is often 260 volts. Most of my machines can handle this higher voltage but the spindle drive in one machine couldn't handle it so I had to put in buck xmfrs. Eric

The rotary converter would help, but so would a simple idling AC motor plugged in next to the welder. It's the flywheel effect that pulls energy from electrical spikes and dumps energy into dips. You could even mount some heavy rotors (with suitable balancing) to the motor shaft.

I guess you could get an estimate by thinking about running a motor open shaft, and assuming that all of the starting current goes into getting the rotor up to speed. [1]

Just as a WAG, assume you have a 1 hp 240 V motor, rated at 6 A full load. Say it takes 1 second to come up to speed and takes 3x the normal full load current to start (even when it's starting open shaft). Then you have 18 A * 240 V * 1 s = 4320 watt-sec of energy stored in the rotor. [2]

If you wanted to take energy back out for 0.5 seconds, and you didn't care if that completely stalled the motor down to zero RPM, you could get a maximum of 8620 watts back out of it in that time period. Or, if you wanted to take energy back out for 2 seconds, and going to 0 RPM is OK, you could get maximum 2160 watts back out of it. In reality you will get less, but this should put an upper bound on it.

Adjust as needed for the size of motor you are thinking about, how much startup current you think it draws and for how long, and over what period of time you think you will need it. Probably the shortest period of time to consider is 0.0167 sec, one 60 Hz cycle.

Matt Roberds

[1] In reality, some of it goes to heating up the windings and the bearings, pushing air around, etc. [2] OK, VA-sec, power factor, and all that. I'm just trying to make an estimate here.