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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
For the lower voltage caps i will use 400 Volt poplypropylene and silver mica caps , they have low loss and good freq response. should arrive in a few days.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Patrick -
For each of your R-C modules, the lower capacitor plate/gradient ring is "floating", not electrically connected to the lower resistor terminal. Why is this? Is there no danger of corona between the sharp edges of the clearance hole in the "washer" and the resistance element on the OD of the resistor?
How did you determine the appropriate distance between the lower gradient ring and the lower resistor terminal? Was this distance based only on the desired capacitance between the plates?
In the similar R-C module construction shown in the J. Power thesis, the gradient rings are electrically & mechanically connected to each end of the resistor.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Herr Zapp wrote ...
Patrick -
For each of your R-C modules, the lower capacitor plate/gradient ring is "floating", not electrically connected to the lower resistor terminal. Why is this? Is there no danger of corona between the sharp edges of the clearance hole in the "washer" and the resistance element on the OD of the resistor?
First, both plates are connected to the ends of the resistor. in order to optimize the field geometry so the mid point V-drop of the resistor matches the location of the Mid point E-field of the same cap i needed about 3mm of length on one end past the cap plate. it is attatched to the resistor, not floating, also there is 4000volts of insulation between the plate and resistor body, no corona danger at all, only 800 volts difference is present.
Herr Zapp wrote ...
How did you determine the appropriate distance between the lower gradient ring and the lower resistor terminal? Was this distance based only on the desired capacitance between the plates?
No, it wasnt the capacitence that was the deciding factor, it was the V-drop/E-field location, the capacitance is merely incidental, i worry 4-5pF is to low.
Herr Zapp wrote ...
In the similar R-C module construction shown in the J. Power thesis, the gradient rings are electrically & mechanically connected to each end of the resistor.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Patrick -
Thanks for the clarification; I've have been following your probe development with interest. The FEMM model seemed to show the lower plate as electrically, floating and none of the photographs show a close-up of how the plates are physically connected to the resistor. At the bottom end of each module, some of the photos show what looks like pink tape wound around the resistor body, under the epoxy. Looking closely at the rest of the photos I now see the little jumper wires connecting the resistor terminals to the cap plates, partially buried in all the goo.
Have you get your calibrator figured out yet? That will be essential for "qualifying" your probe design.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Herr Zapp wrote ...
Patrick -
Thanks for the clarification; I've have been following your probe development with interest. The FEMM model seemed to show the lower plate as electrically, floating and none of the photographs show a close-up of how the plates are physically connected to the resistor. At the bottom end of each module, some of the photos show what looks like pink tape wound around the resistor body, under the epoxy. Looking closely at the rest of the photos I now see the little jumper wires connecting the resistor terminals to the cap plates, partially buried in all the goo.
Yeah in the FEMM model you can specify that the lines enclosing a shape, are at a certain voltage, with out "wires" being visible.
Herr Zapp wrote ...
Have you get your calibrator figured out yet? That will be essential for "qualifying" your probe design.
Herr Zapp
Great minds think alike.... and no im trying to get that figured out now.
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High voltage probe for O-scope, 1 of 2, ( DEVELOPMENT ).
