Weak Arc on Lincoln 225 ac

[the old grind]

IT, we're just thinking that when one leg is positive the other is negative AKA 180^ apart, no? The average across both hots (240v) is still RMS and still 60 Hz, and I don't see both legs being in the same phase if the x-former on my pole is fed by one wire and is obviously 1 Ph. Warm up that o'scope and show us a trace or two lest we remain confused.

btw, I have sound & light meters, refractometer, thermal cams/scopes, inline and clamp-on ammeters, etc but still lack a scope. If yours is idle, is it for sale?

 

[Fuddy1952]

Now "I can take a scope and make it look like anything I want for starters." makes absolutely no sense whatsoever, just like putting four 6 volt batteries in series equals 48 volts.
At this point, the conversation to understand one has to eliminate ego, hurt feelings, "I'm smarter than you"...the list goes on.
An oscilloscope beam scans across, with adjustments for sweep time (x) and amplitude .
Industrial's battery analogy is good (forget voltage is wrong) because if you series four 6 volt batteries all + to --, then from one end to the other you have 24 volts. From center (2 batteries either side) you have 12 volts.
So now residential current. The neutral (ground) is analogous to this center batteries connection.
Incoming you have the neutral (ground) which is the power transformer center tap. The other two transformer leads you have 240 volts across, half that or 120 volts from neutral to either lead.
Oscilloscope probe takes two wires. Wire on neutral then either transformer outer lead you see the 120v(rms) sine wave. From outer leads you see 240v(rms) sine wave.
Sine wave peaks at about 170v (120vrms), 340v (240vrms).
Back to batteries example. Oscilloscope leads across all batteries you see the sweep line go up to 24v, reverse leads line goes DC own to 24v. Same with lead batteries center up to 12v one end, down to 12v other end.
A line since voltage is constant (DC).
THIS is so important understanding oscilloscope on AC. Across transformer outer leads the sine wave 240vrms. However! From center neutral to one lead a sine wave...but as THAT sine wave rises, the other lead falls. They ARE NOT in synchronization! Those two 120vrms sine waves are 180 degrees OUT OF PHASE with reference to neutral. Exactly like the battery example. From center one end it's positive 12v with respect to center. Center to OTHER end it's NEGATIVE with respect to center.
Hope I've made it clear. The YouTube guy is correct.

 

[k0ua]

I dont know a lot about electricity but my 3 prong welding plug has 2- 110v that if you check each lead to the ground you get 110 on each leg so I always assumed that both 110v legs went back thru the ground lug to complete the circuit.

The ground lug is NOT involved in powering the welder. The two 120 volt legs are on different phases. Therefor 240 volts are developed between the legs. The welder uses this 220 volts for its power. No neutral, and the ground is a safety ground, and no current flows on this ground wire.

 

[Fuddy1952]

The ground lug is NOT involved in powering the welder. The two 120 volt legs are on different phases. Therefor 240 volts are developed between the legs. The welder uses this 220 volts for its power. No neutral, and the ground is a safety ground, and no current flows on this ground wire.

Thanks. Correct.

 

[Industrial Toys]

I got to thinking about my 10hp rotary phase converter, and how you can use those two legs as phases and then make up your third phase with a capacitor based phase shift circuit. So, I have to confess, I am CONFUSED. :confused3:

If for no reason, that those two legs won't be 120 degrees out of phase???

 

[BukitCase]

The capacitor phase shift part only works (with the two 180* single phase "legs") to get the 3 phase motor running; then the phase shifted leg cuts out (like a single phase starting cap) and the 3 phase motor continues to run on the two single phase (180* apart) legs - but ONLY at about 65% of its normal rated power.

A SERIOUS RPC uses a single phase motor to run an actual 3 phase GENERATOR - more elegant, but kinda limited by the size motor that's available for single phase "household" current; at about 80% efficiency, a 5 horse single phase motor might get you 4 horsepower.

I haven't worked on much 3 phase stuff, so can't really explain how a 3 phase motor is used to get a 3rd phase on THAT type of converter, other than the motor is used to phase shift at least ONE of the two single phase legs (I think)... Steve

(keep in mind that capacitors aren't the ONLY component that can shift phase; so can inductors - like motor windings, for example)

 

[Industrial Toys]

When you say "Generator" do you mean an idler motor or the idler is then connected to another generator still?

 

[BukitCase]

In my previous post I meant just a simple single phase motor directly driving a 3 phase generator; no idler motor involved. For something with an idler motor, I had this bookmarked (at the time, I was considering older 3 phase stuff like a lathe and mill)

diy - How to Build a Rotary Phase Converter to Convert Single Phase to Three Phase

Since you asked about an idler motor, you may already be familiar with that method... Steve

 

[Industrial Toys]

Yes, I have a 10hp home built 600 volt Rotocon. Built it to run a Lincoln Mig Welder, but the computer in that never liked the fake 3 phase. AND I never liked starting a 10hp rotocon everytime I wanted to weld.

 

[BukitCase]

Thought you might :=)

Here's an example of the "simple" 1 to 3 I first mentioned -

1-to-3 Power Source Generates 3-Phase Power from Single-Phase Input

(Obviously NOT a "home owner" cost factor)

From what I've read in the past, it seems like MOST applications for home use would best be served by a SEPARATE VFD for each piece of equipment (VFD's don't seem to appreciate being "passed around", or "home grown" switching methods much) - plus, the soft start option could be handy. My little Grizzly mill is geared, 6 speed and (if I EVER run low on projects) I've considered adding a VFD; both for the "in between" speeds, AND the soft start. Doesn't take a very heavy tool for that surge start to get a bit jarring... Steve