Argh! Must buy new welder.... Must buy....

[Beuford]

I hate when something I want is discontinued - it makes me go buy one before they disappear. I'm now the proud owner of a Hobart Ironman 230.

I looked at the new Ironman 240, and I did note that the 240 specs were very close to the Miller 252 which was interesting. But for me simple beats complicated; I prefer taps over one more circuit board to fail. The other thing that swayed me is that the new 240 spec sheet had this note (where the 230 did not):

"Note: Running off of generator power is not recommended for the IronMan 240."

I don't like limitations like this, particularly since I've had to run off generators before. Sometimes it's just more convenient than a REALLY long extension cord. I wonder if this is a function of the infinitely variable voltage system on the 240?

BTW - does anyone know how the infinitely variable voltage output systems actually work? I'm wondering if its an inductance or phase control type system. I ask this because I noted that the KVA of the 252 and new 240 are MUCH higher than the 230. The 230 has a KVA of 7.4 for an output of 6.3KW (85%), while the 240/252 has a KVA 11.4 for an output of 7.1KW (62%). It seems that the power factor on the 230 is much better at rated load than the 240/252, and the only thing I can think of is if they are somehow manipulating input voltage/current phase on the 240/252 as a means of controlling output voltage.

Anyone know what's going on here?

Just curious.

Beuford

[Willie B]

Inverter VS Transformer?
That is NOT a statement, I don't know.

[Beuford]

Inverter VS Transformer?
That is NOT a statement, I don't know.

No, they are both transformer units.

I think I answered this question myself. The schematics for the 240 shows a pair of SCR (silicon controlled rectifiers) on the output circuit. These can be phase-modulated to control current flow, but because of how they accomplish this the voltage/current gets pushed out of phase (more so than just from the induction of the transformer). The resulting phase shift reduces power transfer for a given input voltage and current.

You can see this in the specifications as an increase in peak current requirements for a given output. From the Hobart spec sheets for these products you can see that the Ironman 240 does put out a somewhat higher rated welding current (200A vs 175A for the Ironman 230), but it requires a much larger input current to achieve that output (~51A @ 240VAC for the Ironman 240 vs ~31A @ 240VAC for the Ironman 230).

The benefit of having the SCRs is that you can control output voltage with an electronic circuit rather than a tap switch, and they can replace a contactor (big relay) on the output that can wear out. The drawback is that more input current is required for a given output. The use of these SCRs is also probably why Hobart does not recommend running the Ironman 240 from a generator.

Beuford

[Louie1961]

I believe it is phase angle controlled or a combined phase angle/zero current crossover controlled firing pattern. Just my wild *** guess though.

http://www.freepatentsonline.com/3883714.html

[Broccoli1]

interesting that the IM240 states that about running off a generator but the MM252 does not.

I've run my Mm252 off of a Honda EU 6500