On 3/7/14 2:02 PM, David Speck wrote:
Dave,
I would also place suitably rated, beefy MOVs across the input and
output leads of the bridge, and possibly across each individual leg of
the bridge. Rearranging the wiring have caused the system to pick up RF
in a new way that is blowing the bridge.
MOVs in a system where there are spikes all the time is a recipe for
disaster. Each time they clamp, they die a little, and conduct a bit
more leakage current. I learned that on the 3 phase motor drive
scenario.. Kill a big fat MOV in hours.
If you want a clamp, use a gas tube type or a semiconductor device.
They can clamp millions of impulses.
I'd also place suitably rated 0.1 uF ceramic disc caps across each leg
of the bridge to bypass stray RF. Electrolytic caps are too slow to
protect against RF at TC frequencies.
0.1 uF will result in some noticeable leakage at 60 Hz. It's about 27k
impedance, so you get about 10 mA. Probably not a big deal in this
application, but it's more than enough to trip a GFCI.
Series L might be a better approach to filtering.
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