Reccommend me An Everlast Tig Please

@posixPilot

I had the exact same discussion with Ken last year.

And he is correct.

While it is true that the utility company provides you with single phase power, the transformer center tap creates a 180 degree phase shift between the two legs.

Which is why you can split circuits with a single neutral.

rivets

Just another question I have. With the 200DX, am I able to use a plasma cutter, and does it come with one? If not, how much extra is it?

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Originally Posted by kenwhite

Mike it works exactly as I described above. Phase describes the shift in time, or degrees, between 2 signals. Meters measure the difference between 2 voltage points, not the sum between 2 voltage points so the voltages don't cancel when when out of phase.

A 180 degree phase shift means one voltage is going positive while the other is going negative. When you connect a meter across the 2 phases, it measures the voltage difference between the two wires, which means it subtracts the voltage measured at the negative lead from the voltage measured at the positive lead. So, 120V - (-120V) = 240 VAC

If you measure 2 voltages of the same phase, for example across the hots on the same branch or same part of the transformer, you get 0 volts -> 120V -120V or -120V - (-120).

EDIT: The voltage values I'm using are RMS values and not the instantaneous values that actually generate the peak positive and negative values so that may be what is confusing you.

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Well I am easily confused so I thank you for helping to clear that up... I think my understanding is oversimplified. so how does this all translate into load carrying capacity of wire. at 110? 220? I guess that is what I am trying to figure out. I understand how 110 uses a common and that I can share a common. at 220 do the two load carrying conductors effectively become one another common as the current oscillates? does this reduce or increase current carrying capacity of the conductor?

Thanks for your help, you seem very knowledgeable and I would like to dispel any of my erroneous bar room logic once and for all..

Wade.

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Originally Posted by tt ws6

Just another question I have. With the 200DX, am I able to use a plasma cutter, and does it come with one? If not, how much extra is it?

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No plasma cutting with the standard Tig machines. You could look at a multi-process machine, or go with a dedicated tig and a small plasma.

http://www.everlastgenerators.com/Po...05-379-pd.html

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Originally Posted by kenwhite

Wade, you do inderstand most of it.

The 240 VAC load does not use a common, it uses 2 hots that both see the same current through them, and a safety ground that does not see any power current unless there is a fault.

If you look at the load as a constant power, where voltage x current = power, you can see that when the voltage is doubled, the current through the line is reduced to half.

Since current through the line is the primary limiting factor when sizing cables, a 240 VAC branch can use a larger AWG, smaller diameter, cable for the same power load.

Cables and breakers are sized by the National Electric Code (NEC).

Oh, the reason a Dryer connection uses 4 wires -> 2 hots, a common, and a safety ground, is because it typically needs 240 VAC for the heating element and 120 VAC for the control, sensor and lamps.

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Thank you Ken that confirmed what I always thought, One last qestion, I think I read something posted by Mark saying that the duty cycle of the machine affects the size of the power cable you can use to it..I.E. higher AWG, (Smaller Diameter) knowing the machine will have to rest. and would this apply to a breaker as well? I am just wondering how Griz is able to get away with a 30 amp breaker with his 250ex. I think he started this whole debate.

Ken,

Thank you for indulging my curiosity on this one. Below is a diagram that I think describes the circuit that you mentioned ... where 2 AC sources in series, and 180 degrees out of phase subtract one another.

Attachment 4733

But, I think I also now understand what you are referring to with the RMS calculation of potential. Where as this diagram shows the instantaneous electric potential relative to zero, RMS measures absolute potential, or the maximum difference between the peak voltages for each AC signal. Is that correct?

I knew that voltage across a transformer would create a 180 degree phase shift on the secondary, relative to the primary. However, I did not know that there would be a phase shift with in the secondary windings, relative to a center tap. If I were to scope a center tapped wall-wart transformer (signal A left tap to center tap, signal B right tap to center tap), would I see the same phase shift?

Thanks
Mike

I find my self in good company then ;) .

Cheers
Mike

If we didn't have inverter type welders, this discussion wouldn't be happening. Those transformer type welders still have a place in this world. The inverters are more than twice as efficient as the transformer types for the same capability.

For automotive applications, TTws6 wouldn't be welding stuff over 3/16", maybe 1/4" on occasion.

Ken White has done a fantastic job of explaining how those pesky electrons flow into, through, and out of our magic spark boxes.

There is always something to be learned on this forum.

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Originally Posted by posixPilot

..... RMS measures absolute potential, or the maximum difference between the peak voltages for each AC signal. Is that correct?....

Mike

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Mike,

Since "M" in RMS stands for "mean" or average, then RMS voltage is always less than peak.

So 120 volts RMS would produce the same power in a given resistive circuit as 120 volts DC, even though the AC peak is ~170 volts.

Cheers,
Andy

Right, I'm familiar with RMS ... it actually approximates the area under the curve based on the peak voltage. Normally we measure voltage relative to zero volts. But what Ken helped me realize is that with a second out of phase signal, the potential is measured relative to the peaks of both signals, instead of zero.

Cheers
Mike

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Originally Posted by kenwhite

Well, if the welder is connected to a dedicated circuit, i.e. nothing else will ever be connected to it, then the branch can be sized with lower rated current carrying components than the welder actually draws. If the branch circuit has the possibility of having a higher current draw, non duty cycle load connected to it, then it will trip the breaker relatively soon which is why a larger sized branch is needed for multiple load branches.

It is possible to operate low duty cycle devices on lower current rated branches because circuit breakers, and fuses, are thermal devices that trip, or open, when over heated over a specified time period. Since low duty cycle devices draw power and create heat for a small finite period of time that is typically much less than 10 minutes over a defined 10 minute duty cycle period, the thermal devices will heat for a short period of time and then cool for a longer period of time and therefore not trip.

This is why Griz can use a lower rated current branch and not have excessive breaker tripping -> plus the welder/plasma cutter only draws maximum current when operating at their maximum thickness limits.

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Thanks Ken you firmed up my understanding and dispelled a few misconceptions for me. This thread is taking on an interesting new character.