The task of creation of a new generation of switches was set forth in
the ITER research and development programme. The set of switches consi
sts of circuit breakers and making switches both for normal and protec
tive mode of operation. In addition, there may arise a demand for a po
larity reverser to change the output current polarity of the supply co
nverter. All of these switches are to operate with steady state curren
ts of about 40 kA and voltages of up to 20 kV. The required response t
ime is not more than several milliseconds. In this paper the results o
f development and investigation of several multiaction mechanical swit
ches for the ITER power supply and protection systems are described. A
n extensive test programme was carried out to check the design concept
s of the switches and determine their real parameters. The results of
the experimental study indicated that all of these switches can be use
d as the basis for the design of the ITER switches.