The motor case floats.
On Monday, July 27, 2020, 06:53:12 PM CDT, shaun <snoggle@xxxxxxxxxxxxxx> wrote:
Does the motor case and variac share the same ground.
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Terry Oxandale
via Tesla
Sent: July 27, 2020 4:52 PM
To: 'Tesla Coil Mailing List'
Subject: Re: [TCML] **External Email** Re: DC motor fuse/rectifier issue
Blows only under higher powers, and could be related to ground strikes or
strike rail strikes. There is a lot going on when I bump up the power, and
the death of the rectifier or fuse has some component of time delay before
the obvious slowing of the rotor disc is noticed. I do know that I've had
ground and rail strikes that did not result in this issue, so no definitive
or observed issue that I can find that has an obvious direct correlation.
Terry
-----Original Message-----
From: Tesla <tesla-bounces@xxxxxxxxxx> On Behalf Of shaun
Sent: Monday, July 27, 2020 1:20 PM
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Subject: **External Email** Re: [TCML] DC motor fuse/rectifier issue
I use about the same setup with a 3hp dc motor and not blowing fuses, the
bridge does get warm. Can you just run the motor on the floor by itself.
Also does the fuse blow right away or ever time. Sounds like you have an
short in the wiring.
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Terry Oxandale
Sent: July 27, 2020 1:51 PM
To: tesla@xxxxxxxxxx
Subject: [TCML] DC motor fuse/rectifier issue
I'm using a permanent magnet DC motor for my ARSG. Power is through a
variac, to a diode bridge, and then out to the motor under the coil. The
issue is that I can't keep the fuses protecting this circuit, nor rectifier,
intact. I use a 10 amp fuse at the control cabinet for protection (just off
the 120vac hot leg of a 240vac source), and the DC supply cable for the
motor is surrounded by grounded braided copper. I have an ammeter to monitor
the motor, which indicates proper draw during runs (2-3 amps depending on
speed), yet the cheap bridge (50 amp/1000 v) gets warm fast, and also does
not endure an extended run on the coil. A while back I created a filter of
sort to smooth the full-wave pulses (cap/reactor), but that made things
worse, so that was removed. I don't have a sufficient understanding of the
induced currents associated with these coils, and hoping someone here can
help. I have yet to determine if a failed bridge is the cause of the fuse
blowing, so I may insert
some fuses at different points of the circuit to find out. My assumption
is the rectifier (very cheap ebay item) could be at fault, but there is a
lot of knowledge I lack about what impacts of these coils on
surrounding/supporting circuits. Any thoughts on what can do to resolve
this?
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