
Power Electronic Converters for Motor Drives 53
is positive, thyristors T2 and T3 are fired simultaneously.
The output voltage V
a
, is shown by the solid line in Figure
2.8.
There are two pulses per mains cycle, hence the descrip-
tion '2-pulse' or full-wave. At every instant the load is either
connected to the mains by the pair of switches Tl and T4, or
it is connected the other way up by the pair of switches T2
and T3, or it is disconnected. The load voltage therefore
consists of rectified chunks of the mains voltage. It is much
smoother than in the single-pulse circuit, though again it is
far from pure d.c.
30°
120"
a b
Figure 2.8 Output voltage ...