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Electrical 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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There is normally a relatively large but brief inrush current when any transformer is switched on. Striking an arc would normally just increase the current for the duration of the weld. If the problem is voltage drop while welding, you can't easily fix that without the new utility transformer. If the problem is the brief inrush when turning on the welding machine, then a rotary converter might reduce it a little bit by providing some of the third leg current from motor inertia, but the reduction would probably be small since all of the power still has to come in as single phase (not that I have tried it, it could be a bit more effective than my guess and the welding machine would probably work better on 3-phase).

The usual solution to the starting inrush current problem is a soft starter. A search on 'transformer soft starter' turned up a manufacturer of soft starters with specific mention of transformer soft starting, although many of these designed for motor starting will also work with a transformer within ratings. These units gradually ramp up voltage when turned on, and would be used to turn on the welding machine instead of the switch on the machine, which would be left on. A properly sized soft starter could effectively reduce starting inrush to less than normal welding current.

for example:

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They or other soft starter manufacturers would probably be willing to recommend their most appropriate soft starter from the welding machine nameplate ratings, and probably worth getting their advice since it is a somewhat non-standard application.

Reply to
Glen Walpert

Does he know if the welder already has Power Factor Correction capacitors? As I understand it, they can help make an inductive load (transformer) act more like a resistive load to the grid, at the cost of a slightly higher idle current. The inrush current drops (reducing voltage changes on the grid) but the total power through the device as measured by the meter remains the same.

I don't know if they significantly alter the welding experience, I suspect not.

Hope that helps, --Glenn Lyford

Reply to
Glenn Lyford

Whidbey Island is always going to have power problems. It is too close to the edge of the grid. I would invest in a used, industrial, diesel or natural-gas generator to run his weld shop from. A used rental unit could be just the ticket.

Reply to
Ernie Leimkuhler

I can sell you a MEP-007A 100 kW generator. 37 hours only on the meter.

i
Reply to
Ignoramus8530

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