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Re: What efficiency?!
Richard,
Thanks for this info (BTW, thanks also for doing the 2-cap
expt under more rigorous conditions than I employed)....
> I have made about 20 rogowski coils and all worked OK, but they can be
> troublesome if you are looking for wideband response.
>
> I usually take a piece of tygon tubing about 3/8" in diameter and about
> 16" long. I put one end in a lathe and slowly tight wind wire wrap wire,
> 28 gauge kynar insulation, onto the tubing.
>
> The tube is then bent together to form a circle or closed loop. I put a
> plasstic plug in the ends to hold them together. I next get a .01 ohm
> resistor, carbon only, and shunt the coil out (short it) then I mount the
> resistor and coil connections to a female BNC jack and place all on a
> plexiglass frame which has a piece of PVC pipe through the center of the
> hooped coil. the wire with the current to be measured is threaded
> through the pipe and connected.
>
> Next I calibrate the coil using a scope a cap and a discharge circuit and
> figure backwards from the measured ring wave frequency, the L of the
> discharge circuit, and then the surge impedance sqrt(L/c) from there and
> then the actual peak current from there. I try and do this for the
> frequency near that of what I want to measure. Note that the Rogowski
> coil has its own natural frequency too and this will appear as a bunch of
> trash (mini-ring wave) on the first sine's rise in the damped wave you
> are measuring. Ignore it.
>
> The rogowski is effectively limited as described here to a 1mhz limit.
> The one for a TC secondary would need to be much bigger.(insulation) The
> guys at CEBAF wind their own on hula hoops!! For megamp currents and
> integrate over time with IC op amp integrators.
<snip>
Basically a current transformer. What I envisaged was to place the
coil around the grounded discharge rod (LV end of things). I had
trouble imagining why sec. current should be so difficult to measure.
Malcolm