3.4 Ohmic Bucket Capacitor Bank and Controller Two ohmic bucket capacitor banks were designed and constructed for mass driver two testing. The first one was a 1 KV, 10,000 unit which is described in detail in APPENDIX I. Modifications to the circuit since that report was written include: elimination of over voltage protection circuit, disconnect on tether, single 60A fuse (replaced with 20A fuses on individual capacitors), addition of mechanical shorting bar, addition of current shunt on negative side of capacitor, elimination of case ground, a DPDT was substituted in place of the SPST relay with a 50 clamping resistor on the relay input, and an auxiliary SCR trigger circuit was added to insure that the "turn on" SCR latched properly. This circuit is shown in Fig. 3.8. The previous SCR trigger circuit had a 3 ps pulse width (used in drive circuit) which was not on long enough to have the SCR latch due to a very small di/dt. The controller circuit that was used to sequentially fire the ohmic bucket, fire the injector after some delay, and finally turn off the charging is shown in Fig. 3.9. The first ohmic bucket capacitor bank was normally operated at 800 volts. Later energy transfer calculations showed that a higher current was required by the heavier buckets. The calculations also showed that 1500 volts would be required for the = 0.514 bucket in order to obtain 500 g's acceleration. Therefore a new ohmic bucket capacitor bank was designed to meet this requirement with a large reserve margin in voltage if higher acceleration tests were desired. It had a maximum voltage of 2 KV, a
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