Capacitor banks are used to compensate the reactive power demand of la
rge commercial and industrial loads. When used to switch capacitor ban
ks mechanical breakers generate large current transients. These transi
ents may cause serious system disturbances, premature wear of the brea
ker contacts and, possibly, shorten the life of the capacitors. While
thyristor switches are not new and industry has successfully used them
to obtain transient-free switching of capacitor banks, there are very
few papers, describing this application. This paper tries to fill the
void and presents a comparative study of various three-phase configur
ations of semiconductor switches intended for low voltage (600 V and l
ess) distribution systems. Simple theoretical analysis enables the cal
culation of the optimal switching times to minimize transients. These
calculations take into account the system impedance and the initial ca
pacitor voltages.