2 phase on TRIAC- Seam Welder device

[umery2k75]

2 phase on TRIAC



We have installed this Seam Welder in our industry. This diagram was made by their engineer who came here. I asked him, why it has more power in two phase compared to single phase and neutral. He said two phase have more power, because this means their are two power sources. I wasn't convienced by that time. Now he's gone.He told me this operates on two phase 120'. I want to know if I apply 1 phase and 1 neutral on the terminal. This is two SCR back to back, a TRIAC.Won't it have greater power, as compared to two phase, because in two phase 120' apart is the problem. it would bring more hinderance, there is smaller limit. in 1 phase and 1 neutral there is no phase angle problem, so current moves freely. In above there's limitation.I have seen welding unit, by which people do electric welding. They are also double phase. I remember one funny incident, when a person puts on it a single phase grinder black and decker on a double phase, he thought the other line was COLD, but both were hot. It burns right on the spot, as soon as he presses the button, hardly turned 2 sec in operation.With smoke comming out from grinder.The concept is that, which is on my brain is that. Suppose you take two wires with 0' out of phase. You get zero power, because no potential difference is their on the terminal. As you increase the phase difference, you get more power.180 I believe is the point where you get the most phase angle difference and most power. Why care about this, when I can put phase,neutral. There's no limitation due to phase angle, because there will be no phase angle issue, as the other line is NEUTRAL.

 

[umery2k75]

any clue

 

[umery2k75]

HELLO

 

[umery2k75]

:|
I found this thing for reference on the internet, regarding two phase on triac.

 

[umery2k75]

:| 

 

[umery2k75]

:|

 

[umery2k75]

Today, I had a discussion on this context with a friend.We follow a hierarchy of facts, which lead to a reasonable conclusion.
1)First, it was decided whether or not 325KVA welder can be powered from a single phase supply as oppose to double phase, as it's originally is.
We agreed, it's quite possible, no doubts.
2)Friend, wrote down two formulas P=VIcosΦ and P=√3VIcosΦ. The second one will be used here, as we are using two phases 120 degrees apart.
3)Next, I did the rejection of the KRITON slang idea.I tell you about the slang idea.During the commissioning of this seam welder machine. I was their standing and I asked their KRITON expert, this question. He try to convinced me, to believe that two phase has more power than the single phase, to support his idea. He gave me relevant example of fabrication welding plants. These plants are small,portable and are used by hands. High power welding plant is always 2 phase, low power welding plant are always 1 phase. His example was correct, but do not support the logical reasoning asked here.
4)Next, I thought about the primary side of this transformer fed by two phases. As I know, I cannot over powered the transformer, as power is dictated by core cross section area and it's fixed. So it was well understood, whether I use single phase, double phase. Power being fed into the transformer cannot be increase/decrease. It depends on the core cross section area.
5)We need to decide, so what's the advantage for using double phase as compared to single phase, if power of the transformer depends on the core cross section area(which is true) and not on phases. My friend points out that the voltage would be √3 times more when powered from double phase , so current has to go down, to keep the power constant as dictated by core cross section area. Next we aim that, the transformer designer can now use thinner copper winding, it would increase their economy for both financially and electrically because of I2R losses minimizing.
6)Then, I asked to myself, can this transformer be driven from a single phase source also? I led to a conclusion that doing this can be proven fatal to the transformer, because driving from single source would affect it's input impedance.Here,I would not want to go into the mathematical impedance calculation. I would like to simply say, driving from single source, the transformer primary appears to be of lower impedance, resulting in a higher flow of current.Driving from a double phase, transformer primary would appears to be of higher impedance. This transformer primary winding can be fried, if driven from single source.
7)Summarizing the result. I would say manufacturer's do this, because this saves copper and help them save money. Secondly due to I2R losses.

 

[FvM]

Basically, the copper weight needed for a transformer does not change when you build it for a different voltage. So the
manufacturer does not not save money. At lower input voltage (and respective higher current), you possibly need
a larger connection cable cross section, partcularly a high power levels.

The main reason, why welding machines are mostly designed for two phase connection is limited current capability of the
supply net. I'm refering to standard 3-phase supply nets, particularly 230/400 V. Countries with low voltage (115 V) supply nets
e.g. the U.S. have special designs like two-phase 230V connectors (180° phase angle) to supply high power loads.