Has their been any consideration to using Triacs for the ctive (but not neutral) switching- particularly for three phase?
Hm, I can answer my own question. 40A RMS would generate about 25-40watts * 3 (for three phase). Too much heat.
Yes, too much heat... tendency to fail unsafe (closed) and also a fail of UL safety standards as Triacs / Solid State Relays can have residual voltage on the lines.