Voltage converter with GTO thyristors in {HEAD ~ series connection} with {TAIL ~ at least a choke} with freewheeling circuit 
with
Voltage converter with GTO thyristors in { HEAD ~ series connection } with { TAIL ~ at least a choke } with freewheeling circuit
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH