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Re: ASRG blowing diodes

Original poster: Daniel Hess <dhess1@xxxxxxxxxx>


Is the case of the DC motor grounded/connected to the negative DC motor lead? (Might have to use a meter to see if there's continuity there.) If so, I'm wondering if the propeller shaft is arcing to the motor shaft? This would lead directly to the negative lead of the bridge who's life expectancy would be pretty brief under these conditions.

If this is the case, I would think that the propeller-to-motor shaft may have to be replaced/re-designed in such a way as to prevent arc over.


"Tesla list" <tesla@xxxxxxxxxx>

07/07/2006 06:43 AM
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?