Those arc welder generators...

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Externet
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Those arc welder generators...

Post by Externet » Fri Mar 20, 2009 7:31 pm

Hi.
Those 'almost' portable, driven by a gasoline engine; have a DC generator capable of over 100 Amperes at about 100 Volts.
http://image8.usedvictoria.com/YYJ7924142.1.jpg
http://www.agwsonline.com/images/thumbP1000308.JPG
Would one of those generators work as a DC motor ?
Miguel
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Bigglez
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Re: Those arc welder generators...

Post by Bigglez » Fri Mar 20, 2009 9:04 pm

Externet wrote: Those 'almost' portable, driven by a gasoline engine; have a DC generator capable of over 100 Amperes at about 100 Volts.
...
Would one of those generators work as a DC motor ?
Yes and No. A lot would depend upon how you expect the
new motor to work.

For arc welding the electrical source resistance is made high
by the series connection of the field and armature windings
in the genny.

The goal is to have enough voltage to draw an initial arc,
followed by enough current to melt the weld spot, but not
both, which would quickly ruin the weld. For most hand welding
a constant current gen is used. It may be either AC or DC,
and of either polarity depending upon welding needs.

Switches on the genny adjust the taps that change the
ratio of series to shunt field windings and therefore the
amount of 'arc' power for different welding tasks.

Why do you need a 13hp (100V @ 100A) DC motor?
Go-karts? DIY Prius? Wheelchair racing?

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Re: Those arc welder generators...

Post by Externet » Sat Mar 21, 2009 7:31 pm

..."Why do you need a 13hp (100V @ 100A) DC motor ?"...

Someone who has one of those welders with a bad engine asked me if could be used in his houseboat as propulsion with a bank of car batteries.
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Re: Those arc welder generators...

Post by Robert Reed » Sat Mar 21, 2009 7:39 pm

Just quickly doing the math in my head - I come up with 80 batteries series parralled for a sustainable 100 amp output at 100VDC for several hours. At even #30 per battery, that would be atotal weight of #2400. Thats quite a boat load - maybe more weight than the boat itself! Then theres the charger problem----

13 HP would move the average 22 ft houseboat with full load at about 9 or 10 MPH max. Better he should pick up a cheap 25 HP outboard from the '70s cheap.

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Re: Those arc welder generators...

Post by L. Daniel Rosa » Thu Mar 26, 2009 5:46 pm

Somehow I don't think so. I don't think it is a DC permanent magnet motor being used- the commutator and brush lifespan would be an issue.

I think it's a 3 or more phase generator (like the alternator in most automoblies) with the appropriate bridge rectifier. The brushes would last longer on slip rings and the regulation would be easier.

To use this as a boat motor would require a variable frequency, variable voltage multiphase inverter. Not impossible (probably more efficient that a DC motor actually, unless the geometries are less than friendly to use as a motor) but impractical.

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Re: Those arc welder generators...

Post by Bigglez » Fri Mar 27, 2009 7:47 am

L. Daniel Rosa wrote: Somehow I don't think so. I don't think it is a DC permanent magnet motor being used- the commutator and brush lifespan would be an issue.
Correct. A PMDC motor/gen would be a poor choice for welding.
L. Daniel Rosa wrote: I think it's a 3 or more phase generator (like the alternator in most automoblies) with the appropriate bridge rectifier. The brushes would last longer on slip rings and the regulation would be easier.
The core is an alternator, with stator windings for 'weld' 'aux 120V outlets'
and 'field' - to power the field coil through a bridge rectifier and sliprings.
Residual magnetism is used to 'boot strap' the genny. An inductor is
placed in the weld circuit to increase it's output impedance, as noted
earlier. The weld 'amperage' is set by adjusting the DC field current.
L. Daniel Rosa wrote:To use this as a boat motor would require a variable frequency, variable voltage multiphase inverter. Not impossible (probably more efficient that a DC motor actually, unless the geometries are less than friendly to use as a motor) but impractical.
Correct. Why not use an automatic transmission from a car or
motorcycle with the single speed motor? Silly really. In a
thought exercise all options should be considered.

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