One last note, I did cover the cord between the ASRG motor and the control cabinet with grounded stranded copper sleeve in an attempt to shield the conductor, but that wasn't a remedy.
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Terry Oxandale
Sent: Tuesday, December 12, 2017 7:55 AM
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: **External Email** Re: [TCML] ARSG bridge rectifier failures
Thanks Dave.
Mine is floating at this time, and the same "block" you describe, only of smaller rating. I'm going to shoot for a more expensive, higher rated block and see where that goes. Hope the family is doing well and "Merry Christmas".
Ox
From: David Rieben <drieben@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tuesday, December 12, 2017 7:45 AM
Subject: Re: [TCML] ARSG bridge rectifier failures
Terry,
I had pretty much the same problem with my big coil. I, too, am using a DC motor designed for a treadmill, that is rated at like 130 VDC for the drive of my ARSG. I was using those 1 kV, 50 amp rated FWB 'blocks' for the rectification of the 120 VAC mains, through a 120/140 volt, 10 amp rated variac for speed control. When I grounded the outed metallic casing of the FWB rectifier in question, it would almost immediately get fried once I even started to produce a spark output from my coil! Fortunately, I had ordered a bag of 10 of these FWB units, and I discovered that when I removed the ground from the outer casing and just allowed it to 'float', the problem was solved.
Maybe you could explore this solution for your setup?
David Rieben
----- Original Message -----
From: "Terry Oxandale" <toxandale@xxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, December 10, 2017 9:22 PM
Subject: Re: [TCML] ARSG bridge rectifier failures
>
>
> I'm having an issue with the bridge rectifiers I'm using to power a
> variable speed DC motor for the rotating spark gap. When the coil is not
> energized (but motor is spinning), the diode stays cool, and appears to be
> reliable. As soon as I energized the coil sufficiently to operate with
> breakout, the rectifier gets a little warm, but appears to remain
> reliable. With more coil performance, I notice more heating of the
> rectifier. It appears, after some testing, that the lifespan of the
> rectifier is inversely proportional to the power put into the coil. I have
> a voltmeter and ammeter to monitor the power to the DC motor, and there is
> nothing to indicate a problem (but these are analog meters, and may not be
> sensitive enough to see everything I'm looking for).
> So far, the only variable is the coil's output (performance), so that
> leads me to believe something is back-feeding or being induced into the
> motor's power cord and back to the rectifier. The motor only draws about 1
> or 2 amps through 90 VDC at speed, yet the rectifier is rated at 30 amps
> and 600 volts. I don't run the motor at the full 90 VDC because the coil
> operates best at a lower RPM, and hence a lower voltage to the motor. The
> rectifier is fed through a small variac, whose output then passes through
> the rectifier. The rectifier does have an LC filter to dampen the full
> wave output of the rectifier. I don't know if it's the cheap Chinese Ebay
> bridge rectifiers or not, but am considering building one out of some
> robust diodes that I've had for years.
> Any thoughts please?
>
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>
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