question about driving a DC sync spark gap

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Original poster: "miles waldron" <mileswaldron@xxxxxxxxxxx>

Dear All,

Is anyone using a DC motor to drive an async rotary spark gap? If anyone is
doing this, how is your variable DC power supply built? We are having
consistent CATESTROPHIC failure of the power supply diodes. Not the motor.
The motor is always fine, and the variac is always fine. We are using huge
giant diodes (300V @400A) and they are frying instantly. We have tried
chokes in series, caps in parallel, caps in series, but nothing seems to
help.

Please help before we shoot the DC motor with a 1000 watt CO2 laser, and
rebuild our spark gap using a variable AC motor.

Background:. This is an 11" OD coil 57" tall #18 wire, 15kva pig, 11 to 15
foot arcs.