_R1^ 



1.3 cm- 



-1.3 cm 



NOTE: 



bulkhead plates 



divider plates 



insulated connectiun plate 



insulated cover plate 



outside cover tubes 



resistor heat sink 



SCR heut sink 



semiconductor ins. & heat sinks 



ORl, OR2, OR3, OR4 bulkhead plate "O" rings 

 Bl, B2 firing CCT support burs 



HI 1 tie point plate 



PI 2 current transformer plate 



Figure 3. — Mechanical layout sectional drawing of Freshwater Fish Electro-Motivator (FFEM) pulser. 



set) = 8 msec, the pulse parameter has an effec- 

 tive on-time of ton = ^on times tp = 32 msec 

 and an off-time of toff = Noff times tp = 48 

 msec. Thus the effective duty cycle while being 

 pulsed for the pulse parameter shown (Figure 5) 

 is expressed as follows: 



Percent effective duty cycle: 

 T 100 



on 



+ T 



off 



Actual duty cycle is only one-eighth of the effective 

 duty cycle. 



25% for Y = 6 

 22% for Y = 7 



For two loads which are to be pulsed alter- 

 nately, suppose Son = 2, Soff = 3, and N^w^t ~ 2. 

 The output to these loads would appear as 

 shown in Figure 5b. In this example, the pulse 

 set Non = 4 and Noff = 6 will give a total pulse 

 period of 80 msec for each set (Son ~ 2 and Soff 

 = 3) and in this example there are two sets per 

 load; thus, the duty cycle is 40% per load Num- 

 ber 1 and 40% per load Number 2 when being 

 pulsed or an overall duty cycle of 20% because 

 of the sharing between the two loads. 



Switching circuits.— The high power 

 switching circuitry in Figure 1 is composed of 

 three sets of SCR: 1) routing, 2) timing, and 3) 

 commutation. There are eight routing SCR, one 

 timing SCR, and three commutation SCR. A 

 simplified diagram of the routing and timing 

 circuits is given in Figure 6. For discussion 

 purposes, we represent the SCR with single-pole, 

 single-throw switches. As noted, the switches 

 (SCR) are grouped into: 1) routing switches and 

 2) a timing switch. (The commutation SCR are 

 not shown.) 



Three modes of operation are shown. 

 Referring to Figure 6a, if only one electrode pair 

 is used, one is connected to point 9 and the 

 other is connected to point 10, then when the 

 switch is closed, the voltage E will appear across 

 the two electrodes and current will flow from 



