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On 9/2/15 9:13 PM, David Speck wrote:
John,
Check out eBay for a current transformer. A 50:5 unit will multiply
your DMM readings by factor of 10. They should be available for under
$20 with some diligent looking.
Something like the following would work. (no connection to seller.)
http://www.ebay.com/itm/130895906892
Just be careful to never put current through the transformer (CT)
without having a load, like your DMM on its amperes setting, across the
CT terminals. When unloaded, a CT tries to put out infinite voltage
which may break down its internal windings.
You can put a resistor or back to back zener diodes across the winding
to prevent this. WHen you do hook up the ammeter, it's so much lower
resistance that the current flows through it, rather than the protection
resistor.
Then, you can investigate which arrangement of PFC caps works best for you.
Dave
-----------------------------
I'm at the point I need to add some motor run caps, I'm thinking the
same that go on your ac units in the 40-50uf 330-440v variety unless
someone has a better suggestion. Looks like I will need around 150uf
per transformer I have 3 12/60 NST. Biggest question is do I run all 9
parallel or run about 3 strings of 3 to each? Would before or after the
EMI filters make a difference. Blowing 20 amp fuses on variac, don't
have a clamp meter and my dmm is only good to 10 amps inline. I was
going to add some and then start measuring the current? John Cooper
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