10 



y 



(a) Single Load 



Timing 

 ' Switch 



(SCH) 



lOo- 



■^s 







fi \\ 



7^ 4^ 59 6 



V Y Y Y 



I 



. Routing 

 Switches 



(SCRs) 



9 

 h 



(SCR) 



(b) Multiple Loads (common anode) 



°J lllmln 

 7 / Switc 



J ' /C/'D 



10 o- 



r 



(c) Multiple Loads (phased array) 



"^1 1 I 1. 1 



1 ' 1 ' I ' 1 



6 r 6 , O o 



r r f f 



o 



Routing 

 Switchot 



(SCR») 



Timing 

 Switch 



^SCH) 



Figure 6. — Switch representation 

 of high power switching circuit. 



SCR k and SCR i are turned on, the current 

 flows from voltage source E through path L^, 

 Rl, SCR k, L2, C2, and SCR i. The series con- 

 nected inductors Li and L2 limit the rate of 

 change of current, and the resistance R^ limits 

 the maximum current. As current flows, C2 is 

 charged to the source voltage E. At this time, 

 the voltage across SCR k and SCR i is near zero, 

 and the current is necir zero; thus these two SCR 

 turn off, and C2 has a voltage E with the right 

 hand plate of C2 positive. Next, assume routing 

 SCR a and SCR e are turned on. At this time 

 current flows from E through the path L^, Rx, 

 SCR a, water load, SCR e, and SCR i. Again the 

 inductance Li limits the rate of current change, 

 and Rl in series with the water load limits the 

 maximum current through the electrodes. At the 

 end of 1 msec (the pulse-on time), SCR j is 

 turned on. This places charged capacitor C2 in 

 parallel with SCR i. Discharge current flows 



from Co through the path L2, SCR j, SCR i, and 

 back to C2. This negative current through SCR i 

 cancels the original electrode load current in 

 SCR i, and SCR i turns off. Current continues to 

 flow through Li, Ri, SCR a, electrode load, 

 SCR e, C2, L2, and SCR j even though SCR i is 

 off. However, this current charges the capacitor 

 C2 in the opposite direction to a voltage near E 

 at which time the current through SCR a, SCR 

 e, and SCR j drop below the holding current and 

 these SCR self-commutate. The charge left on 

 C2 makes the left plate of C2 positive which is 

 the wrong polarity for the next commutation; 

 thus, the cycle begins again with SCR i and SCR 

 k turned on. This allows C2 to discharge and 

 recharge with the correct polarity (right plate 

 positive). Again SCR i and SCR k self-com- 

 mutate. SCR 1 is used to insure self-commu- 

 tation of SCR a, SCR e, and SCR j independent 

 of the water load. It is turned on shortly after 



