Open delta thyristor control why use 6 wires

Stephen Biddle over 5 years ago

Hi All

I work on large heaters, which are 3 phase delta, no neutral. Most of the systems use thyristors to control 2 or 3 legs, so far so good only three cables to the heater. Some systems use 3 thyristor connected in series with each phase ie 6 wires. Why is this done? It doubles the cable cost.

Regards

Stephen

0 Legh Richardson over 5 years ago

Hi Stephen,

I have had no practical experience of heavy duty resistive element heaters but looked interesting so had a sniff around and found this link.

http://www.libratherm.com/pdf/(21.5.1)3%20PHASE%20THYRISTOR%20POWER%20PACKS%20POW-12%20(3%20to%2015%20KW).pdf

It appears to be direct thyristor power control of the heating elements. The number of conductors seems to be more like 12 rather than 6 although perhaps one side are taken out to monitor and feedback by a closed loop process control circuit.

Legh
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0 mapj1 over 5 years ago

It only doubles the cable cost if you do not reduce the cross section as the current per core is now lower, and a 6 wire system allows more flexibility to handle supplies that are single phase or split phase.
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