Rogowski Design Sensitivity Tests with Ideal Formula by Stefan Gerhardt and Larry Guttadora
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Explore sensitivity tests of Rogowski design with ideal formulas for sinusoidal variation figure of merit, test jigs, signal levels, and more.
Rogowski Design Sensitivity Tests with Ideal Formula by Stefan Gerhardt and Larry Guttadora
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Rogowski Design Sensitivity Tests Stefan Gerhardt, Larry Guttadora
Formulas For the Ideal Rogowski Basic Formula For Sinusoidal Variation Figure of Merit should be: Independent of Frequency Purely Determined by Geometry As Built a=30 turns/inch=1181turns/m A=(/4)(5/16”+.033)2= (/4)(.0087)2=5.9x10-5 m2 Figure of Merit: 5.6x10-7 V/A/Hz nA0=8.8x10-8 (Vsec/A)
Test Jig #1 Ends close to closed, but not perfect here 10 Turns Linked By Rogowski Current Measured by Pearson Coil
Test Jig #2 100 Turns Linked By Rogowski Current Measured by Pearson Coil
Figure of Merit: Jig #1 Error Bars Large Due to Small Output Voltage at low frequency, Consistent with flat response. Blue and Black for two different scans Ideal value Rolls off above 10kHz
Combined Results • Good agreement with expected sensitivity • Flat response from 40 to 10000 Hz • Vacuum vessel cuts off above 1kHz. (?)
Example of Signal Levels in NCSX 200kA plasma, want to accurately measure 1% of that Need to accurately resolve 2000 Amps Assume (for concreteness) the same hardware as NSTX Rogowskis * Integrator: selectable RC values of 1 to 100 msec (7 increments) * Digitizer: 12 bits, 5V, 2.5mV bit noise Pick RC so that 300kA5V How Big is 1 Bit?
Conclusion Design is Sound From the “Physics” Perspective