Phase Question

[Dan Pro]

I just purchased a:
Hobart TR-300 AC/DC Welding Machine Model TR4-300
The info. plate on the front of the machine describes it as a 1 phase.
The wiring diagram inside has instructions for changing the wiring for assorted input voltages
volts: 208/230/460/575 these are 3 phase voltages.
There are only 2 hot line input connections and a ground.
What is this all about.
I only have single phase electrical and am beginning to worry.
Do I wire for 230 and run it with 240 single phase or am I euchred.
Why does the plate say 1 phase.

[Sberry]

Those voltages can also be had in single phase but hook it for 230 and you are good to go.

[Some Creep]

If it's like my machine (different manufacturer, different machine) you wire it for the 3-phase version of the correct voltage but only use 2 of the 3 power leads for single phase. Is there really no mention of it in the manual?

[tooldude56]

The plant where I retired ran all of their single phase TM400 welders in the 1970s and earlier on 480 volt 1-phase.

tooldude56

[Dan Pro]

Sberry Sberry Makes this sound simple.

Some Creep you refer to splitting off two hots from a three phase supply.
I don't have a three phase.
Two hots from three would still give me two wave cycles rather than one @ 60htz.

Sadly used equipment sometimes comes without a manual.

[Sberry]

I wire the lights for a ball field 480 single. The runs to the outfield are so long the higher voltages make sense.

[Some Creep]

Sberry Sberry Makes this sound simple.

Some Creep you refer to splitting off two hots from a three phase supply.
I don't have a three phase.
Two hots from three would still give me two wave cycles rather than one @ 60htz.

Sadly used equipment sometimes comes without a manual.

Ah, no manual.

Yes, I don't have 3 phase either. My machine works configured for 3 phase but uses 2 of the 3 leads for single phase power. Not splitting off 2 of the 3 hots, using the wiring configuration of the machine intended for 3 phase in the dual capacity of single phase operation. Like I said, different machine, different manufacturer. If yours doesn't do it, disregard the suggestion.

[runchman]

Not that I have an answer for your question, but if you were to use 2 hots from a 3-phase system, you would indeed end up with one waveform at 60 hz.... adding 2 sine waves of the same frequency always results in 1 sine wave at that same frequency, regardless of the phase shift.

The only thing that changes on the end product, based on the relative phase of the 2 component waves, is the amplitude.

There's my electrical engineering lesson of the day

- John

[Dan Pro]

Creep

I misunderstood I hope your right it sounds promising.


John

I am under the impression that the waves peak and fall at different times giving a more even and consistent supply.

[Some Creep]

I didn't really word it correctly in my first response. I re-read what I wrote and it's pretty confusing how I worded it.
In the few years I rebuilt welders I never came across or even heard of wiring done this way. I bought a welder and found it had this funky configuration of wiring it's terminal board for 3 phase but using 2 of the 3 leads (2 specific leads, not just any pair) and hooking it up single phase. I'd recommend doing a web search for a manual on that machine. Maybe there's a manual out there that can be had for free.

EDIT: Hey! It's a HOBART!! Isn't there a manual available through this site??

[Dan Pro]

I looked at the owners manual section but this machine is to old.
I think it was made in the mid 70's

[runchman]

your 'peak and fall' explanation is right for using all 3 phases; with single phase it's just one sine wave as you know.

(In one version of 3-phase): if you use one phase and neutral, you get 120.
If you use any 2 of the 'hot' phases, you get 208. That's probably where the 208 comes from.

That's if each of the 3 phases are 120. I don't know what 'standard' 3-phase systems are.

In general though, with 3 phase, the phase-to-phase voltage (i.e. using 2 hots) is 1.73 times the phase-to-neutral voltage.

more confusion !

- John

[Dan Pro]

Thanks John

Sounds like I should use the 208 wiring option.

[Sberry]

A little too much thought can be a bad thing on occasion, if this is a single phase machine then use the 230 option.

[TOMWELDS2]

K.I.S.S......Cary's right! Dont make it complicated. Standard utility is: 208volt 3phase...240volt single phase. Use the 230volt connections. Hook it up and have fun!