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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