Output pulse transformers were used to provide electrical isolation between the two SCR's being triggered. The pulse transformer consisted of a stack of four ferrite cores used in the drive circuit SCR trigger circuit and wound with fifteen turns of wire on both primary and secondary. These were driven with a Darlington pair which in turn was driven with a Darlington pair with isolated outputs. Inverters with open collectors were used to get the proper wave form to drive the primary Darlington. Since the power supplies operating the recharging controller and SCR trigger circuits were differnt and had different cable lengths, optical couplers were tried so as to prevent ground loops. They were not satisfactory and a futher pulse transformer was used on the input to provide isolation and noise immunity. 4.5 Recharge System Performance Results from testing the recharging system test circuit shown in Fig. 4.2 are now presented. The recharge capacitor bank in that circuit consisted of 16 parallel electrolytic capacitors. The sector capacitor was comprised of 11 surplus PPA capacitors wired in parallel with a total capacitance of 2033 pf. Since the recharge capacitor bank has a total capacitance of compared to of the sector capacitor it can be treated as a voltage source. Measured values of voltage, current, and recharging period are given in Table 4.3. The results of these tests are given in Table 4.4. The results showed that this simplified recharge circuit (over that of a forced commutation circuit) could be used to recharge the sector capacitor.
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