RE: ASRG blowing diodes

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


Mike:

Do you have filter caps on the DC side of the bridge?  You should
compute your required capacitance based on the current, ripple, and
frequency.

I think you want to use 120 Hz because the DC pulses come at that rate
thru the bridge.

So for 1.5 amp and 1 volt ripple I get that you need a 12,500 uF filter
cap.

C = I/(Vripple*f)

Mark


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Friday, July 07, 2006 6:44 AM
To: tesla@xxxxxxxxxx
Subject: ASRG blowing diodes


Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>

I recently put a AR propeller gap on my 6", 4 kVA coil. It performs
very well, Had some 9 foot ground strikes tonight. I run a 28V, 1.5A,
3600 rpm dc motor. Powered by a 6A variac into a 120 to 24 V 5A step
down tranny into a full bridge rectifier (20 A, 200V). This should
easilly run this, and it did for many hours. Varying the speed really
does some interesting things to the character of the streamers! I
decided to run the 24 line to the motor thru some flexible conduit
that I grounded to RF ground (in case of streamer strikes). After a
short time on the 4th, it poped the 2 A slowblow fuse, then stopped
all together. I found that half the bridge shorted, overheating the
tranny some. Replaced the bridge, ran it for 3 hours (not hooked to
the coil) at nominal line voltage, and all was fine. Ran the coil
again tonight, and after a few minutes it blew again! Oh by the way,
I didn't ground the flex conduit this time. How do others deal with
this, is my problem unique?