Page 239 - Power Electronics Handbook

Cycloconverter circuits 229
in Figure 10.7, where only one phase of the converter is shown in detail. If
a single-phase output is required, only one converter is used and the load
output is returned to the transformer neutral point. Interphase connections
are preferable to double star since, as discussed when considering the
equivalent a.c. to d.c. converters, the utilisation of the system is much
higher. The six-pulse push-pull system can be extended to twelve pulses by
using the circuit of Figure 9.10.
Push-pull circuits have a single output point so that there exists a
common load terminal to which three-phase systems can be connected. A
bridge circuit, on the other hand, requires both ends of the load to be
connected to the converter terminals, therefore for three-phase loads
either the different load phases, or the input to the bridges, must be
isolated. Figure 10.8 shows a six-pulse bridge converter with isolated load

h d
I 3
Phose
TH1- TH12 TH13 - TH24 THz - THs
_j
Figum 10.8 Bridge six-pulse isolated load cydomnverter
Conrerler I Converter 2 Converter 3
I

0

I

A c%r3

pbvc 10.9 Bridge six-pulse cyclomnverter with non-isolated load