I have been looking all over the web and finally found and joined this site to get an answer to this question.
Ok, I am working on an old plastic injection machine. It has been badly abused in its 40+ years of life so trying to figure out how it came from the factory is not possible.
It has 3 old heating elements, each controlled by a new digital controller and relay. Each comes on and off independently as needed.
One of the heaters shorted out and tripped the breaker, so I took a look at the wiring. All 3 units were being powered by a 2 tiny wires coming from one phase of the 3 phase power. How it even worked was a surprise. It did take a long time to heat up. (it is a 3 wire system)
I am replacing all 3 heating elements and want to power them efficiently.
Assume heaters are A - B and C
Heater A would be powered by phase 1-2 Heater B would be powered by phase 1-3 Heater C would be powered by phase 2-3
But I am afraid this will result in boosting voltage to 400+, because of the cross connection and ruin everything. Some posts and diagrams seem to indicate this would happen and fry the new heaters.
Option 2 would power heater A from power 1-2, and then power heaters B and C from power 1-3. This would leave one of the phases unused. ( 2-3)
I think I have to use option 2. I have a pro coming over, but I want to know what I am talking about when I try to explain it to him. Plus he is Russian and being able to explain things clearly is critical.
One other thing I found odd. With NO power, there is continuity between terminal 1-2 but not 1-3 or 2-3. With power turned on there is 220V between 1-2-3 in any combination.
Why is there continuity between 1-2 when power is off? Perhaps it has something to do with the rotary phase inverter?