Page 368 - Fundamentals of Magnetic Thermonuclear Reactor Design

Power Supply Systems Chapter | 11 345

circuit was developed, taking into account this factor. It uses three types of fast-
response mechanical switches (Table 11.9): FOS, FDS and fast make switch
(FMS).
The switches are made by a single technical principle providing their unifi-
cation. The main elements of the FOS are shown in Fig. 11.16 as an example.
The switch contact system is made as two concentric current leads, closed
by a movable circular element with a wedge-shaped work surface. The inner and
outer current leads have removable contact rings with silver patches. Both the
current leads and the rings have water-cooling channels. An additional elastic ring
with refractory contacts is used as an arc-resistant element at the final opening
stage. A movable contact with a flexible membrane attached divides the switch
cavity into two chambers filled with compressed air (0.6–0.8 MPa in the lower
and 1.4–1.6 MPa in the upper chamber). The contact system is encircled by four
thyristors connected in parallel with the current leads. The FOS has an inductive-
dynamic drive excited by a discharge of outer capacitor bank through its inductor.

TABLE 11.9 Technical Characteristics of Different Multiple-Acting Switches
Switch type
Parameter FOS FDS FMS
Nominal current (kA) 45 45 60
Nominal switching voltage (kV) 1.0 10 10
Insulation test voltage, (50 Hz) (kV) 28 28 28
Response time (ms) ≤4 ≤4 ≤4
Contact resistance (µΩ) ≤5 ≤5 ≤5
Minimum guaranteed number of operations 5 × 10 3 5 × 10 3 5 × 10 3

FIGURE 11.16 Fast open switch.