Electric help please

A friend of mine here on Whidbey Island has a welding business. It's
pretty new, only a few years now. Anyway, he called me yesterday with
an electrical problem. Puget Sound Energy (PSE) has had complaints
from neighbors about voltage spikes or drops, my friend wasn't clear
on this, but they showed him a graph which I have yet to see. The
solution PSE is proposing is a new xmfr at the pole. PSE told my
friend the problem is because of the hard starting welder. The welder
is an older xmfr type machine with lots of copper. At full load it is
rated at 11 kw, which is about 46 amps. But I don't know what the
current spkies to when he first steps on the pedal. The machine is now
wired for single phase but can be wired for three phase. What he wants
to know is if he ran the welder from a Rotary Phase Converter would
the current spikes and voltage drops be less. I don't know. I also
don't know if there is a way besides my friend paying thousands for
PSE to install a new xmfr on the pole for this situation to be
ameliorated. He can't afford at this time for a new welder with a
softer start setting. Besides, the hard fast start means his employee
can make more welds. Any help would be greatly appreciated.
Thanks,
Eric
Reply to
etpm
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You could look into turning it on with a Zero Crossing Relay.
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Can you check the voltage, current and power fector with a scope?
-jsw
Reply to
Jim Wilkins
I don't know. It may be he needs to talk to the state about it. But it looks now like it is his problem. Do you have a solution? Eric
Reply to
etpm
It depends on the contract that he signed for power, or the regulations in your state.
There's a good chance that anyone using power beyond normal residential use is expected to pay for any necessary upgrades -- it varies by state, and I wouldn't even have a clue as to what the rules are in Oregon.
For that matter, in most places if you want power run to your house you've got to pay for it, by the foot.
Reply to
Tim Wescott
A rotary phase converter may help, but I wouldn't expect it to cut the problem by more than a factor of 2/3, and very possibly not even that. I'm just guessing, though.
There may be soft-start add-on kits out there that will be cheaper than either a transformer or a new welder.
If he's got an established business he may be able to get a business loan. He'd have to be willing to get into debt, and have enough proof of income to swing it, though.
Reply to
Tim Wescott
================= As this appears to be a surge problem, it might be possible to rig up a large three phase motor with a HEAVY flywheel as a rotary phase converter to power the welder.
Reply to
F. George McDuffee
You might look into power factor correction caps for the welder. There's plenty of misinformation about this online without my adding to it, but my understanding is that a welder with PF correction will draw more current at idle, but less under load. Not sure what it'll do, if anything, about surges.
Re who's responsible, in my area there are certain single phase loads that the power company can force you to remove if they cause problems. Single phase motors larger than 5HP, for example.
Reply to
Ned Simmons
I think your understanding is wrong. With power factor correction the current at idle will be less. Under load it will also be less, but the difference may be almost unmeasureable.
But you are right. Correcting the power factor may make things enough better that he will not have to do anything else.
Dan
Reply to
dcaster
. What he
0switching%20types.pdf
Not a good idea. This is from Wiki.
Transformers
When a transformer is first energized, a transient current up to 10 to 15 t imes larger than the rated transformer current can flow for several cycles. Toroidal transformers, using less copper for the same power handling, can have up to 60 times inrush to running current. Worst case inrush happens wh en the primary winding is connected at an instant around the zero-crossing of the primary voltage, (which for a pure inductance would be the current m aximum in the AC cycle) and if the polarity of the voltage half cycle has t he same polarity as the remnance in the iron core has. (The magnetic remane nce was left high from a preceding half cycle). Unless the windings and cor e are sized to normally never exceed 50% of saturation, (and in an efficien t transformer they never are, such a construction would be overly heavy and inefficient) then during such a start up the core will be saturated. This can also be expressed as the remnant magnetism in normal operation is nearl y as high as the saturation magnetism at the "knee" of the hysteresis loop. Once the core saturates however, the winding inductance appears greatly re duced, and only the resistance of the primary side windings and the impedan ce of the power line are limiting the current. As saturation occurs for par t half cycles only, harmonic rich waveforms can be generated, and can cause problems to other equipment. For large transformers with low winding resistance and high inductance, the se inrush currents can last for several seconds until the transient has die d away (decay time proportional to ~XL/R)and the regular AC equilibrium is established. To avoid magnetic inrush, only for transformers with an air ga p in the core, the inductive load needs to be synchronously connected near a supply voltage peak, in contrast with the zero voltage switching which is desirable to minimize sharp edged current transients with resistive loads such as high power heaters. But for toroidal transformers only a premagneti sing procedure before switching on allows to start those transformers witho ut any inrush current peak.
I would contact the welder manufacturer and ask them if they know of any go od solutions. And maybe contact the power company and ask them the same qu estion. He can't be the only one with that problem.
Dan
Reply to
dcaster
Eric - a "soft start" on/off switch might be a possible cure. In concept it turns on the current when the cycle is nearly over and then turns of as the current passes zero. On the next cycle the current is turned a little earlier. After ?? cycles full power is turned on for all cycles. Mouser Electronics shows a 40 amp triac, which is the "switch" in a soft start device, for roughly $2. Probably need a micro controller to control the triac - $.50, along with a pc board & some caps & a transistor or 2. Then a "heat sink" and, probably, a healthy fan. All told, the cost isn't much so someone has probably built such a gadget for sale as an "add on". If you can't find one, look for someone to build it and offer to do some testing for him.
Hul
snipped-for-privacy@whidbey.com wrote:
Reply to
Hul Tytus
Sounds like a phase angle controller powering a transformer which while it works, I've done it on a Xformer for a TIG supply to ramp up/down the current, is electrically very noisy as you end up potentially putting maximum AC voltage into the transformer suddenly rather than the normal build up from zero so high transient currents. I didn't see the effect on the flourescent lights as I was welding but when it was pointed out to me and I had a look they did significantly flicker during the transition phase from 0 to full on power. No neighbours complained and I checked with one about HF interference with their TV and no problems. Subsequently I have gone to an inverter TIG and at higher currents upsets the ADSL modem in the house but I don't know of anyone else having any issues. Likely I should fit a suitable filter at the welder supply but I'm the only one with the issue with losing ADSL connection when welding at higher currents. I think a soft start might work in a more friendly manner.
Reply to
David Billington
Jim, I ehm not sure how to measure power fector with scope. Maybe Boris, he know. Ahl esk him. Actually, how does one go about measuring power factor with a TEK 465B scope? Thanks, Eric
Reply to
etpm
See the table on page 12 of this Miller manual:
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Idle current with PFC is over 10x the current without PFC.
Reply to
Ned Simmons
Greetings Hul, Soft start may not be the ideal. When welding, if a soft start is used, it takes longer to do the weld. This not only translates to lower throughput it also frustrates the worker who wants to get as many parts out the door as possible. I know that for me, as a machinist, even when I worked for someone else, I hated stuff that slowed me down. At the end of the day my pay would be the same but I, like most folks, jest wanna git the job done. Thanks for your suggestion though, it may be that even though not ideal in all situations it will be the best solution. I will consider this when I try to help my friend out. I had to use soft start on one of my CNC machines in the past when the power available was just a little too low. Fortunately for me I was able to adjust the spindle drive for a softer start. Cheers, Eric
Reply to
etpm
urrent at idle will be less. Under load it will also be less, but the diff erence may be almost unmeasureable.
I do not understand the Miller chart. On my own welder , I added PFC capac itors which reduced the idle current. Did not measure the current while w elding, but my understanding of transformers makes me think that while weld ing the imaginary current would stay the same , but the real current would be much bigger. So the effect of power factor correction would be negligib le while welding.
I looked for information on other welders but did not find any.
Dan
Reply to
dcaster
Eric, I had to go look up the contract, but Pacific Power replaced a residential shared transformer for me so I could have 200 amp service. The transformer is shared by three residences. The others did not pay anything.
My cost was $1550, total to the power company.
Your friend needs to get the power company to give him a firm number for a transformer replacement.
Paul
Reply to
Paul Drahn

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