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Changes in the QA and QC of coil insulation

Changes in the QA and QC of coil insulation. INFN - LASA M. Prioli , S. Mariotto, M. Sorbi, M. Statera. CERN – 19 June 2019. QC of the coil insulation.

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Changes in the QA and QC of coil insulation

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  1. Changes in the QA and QC of coil insulation INFN - LASA M. Prioli, S. Mariotto, M. Sorbi, M. Statera CERN – 19 June 2019 M. Prioli CERN 19 June 2019

  2. QC of the coil insulation • The first test of MQSXFP1 proved that the QA procedures and the QC of the coils inter-turn and inter-layer insulation are fundamental in view of the series production • Insulation damages may be less severe than that in coil n. 1 • How to implement the early defect detection? • Ground insulation test • Resistance measurement • PJ method (capacitor discharge) • Ferromagnetic coupling M. Prioli CERN 19 June 2019

  3. PJ method - principle • Charged capacitor connected across the coil under test M. Prioli CERN 19 June 2019

  4. PJ method - principle • We want to detect the internal short across one turn M. Prioli CERN 19 June 2019

  5. PJ method – which parameter • The effect of the shorted turn is • Barely visible on the equivalent inductance • Clearly visible on the equivalent resistance M. Prioli CERN 19 June 2019

  6. PJ method – which parameter • The effect of the shorted turn is • Barely visible on the voltage frequency • Clearly visible on the voltage decay time constant M. Prioli CERN 19 June 2019

  7. PJ method - setup • Oscilloscope • Capacitor bank (up to 400 V) and control unit • High voltage probe • Coil M. Prioli CERN 19 June 2019

  8. PJ method - measurements • Following the analysis, C was set to 20 nF • One turn in short was reproduced • The short can be easily discerned, measurement are repeatable M. Prioli CERN 19 June 2019

  9. PJ method - measurements • Extraction of decay time constant for all quadrupole coils • Coils disassembled from magnet: C1, C4, C6 • New coils: C3, C5 • No defects up to 400 V ! M. Prioli CERN 19 June 2019

  10. PJ method - principle • For the coils of the other corrector magnets: • w: angular frequency • N: number of turns • k: coupling coefficient between coil and the shorted turn • The long dodecapole coil is the most critical • Tested: the short of a single turn can be identified M. Prioli CERN 19 June 2019

  11. PJ method – increase the voltage • C=2 uF, V=7 kV • Test on a decapole coil • VWL of insulation > 7 kV • Short effect not visible M. Prioli CERN 19 June 2019

  12. PJ method – increase the voltage • SPS electronic • C=2 nF, V=5 kV • Test on decapole and dodecapole coils successful M. Prioli CERN 19 June 2019

  13. PJ method – increase the voltage • In house – M. Quadrio, A. Pasini, A. Paccalini • Adjustable C=10 nF – 100 nF, V=2 kV • Tests are ongoing • (250V * 2 + 500V ) * 2 = 2kV M. Prioli CERN 19 June 2019

  14. PJ method – 1 turn more/less • The PJ method cannot detect a wrong number of turns • A different method has to be applied to cover this case M. Prioli CERN 19 June 2019

  15. Ferromagnetic coupling - setup • Oscilloscope • Signal generator • 4 quadrants PC • Low AC voltage (36 V per coil) • Pickup coil • Ferromagnetic core • 2 coils ~ M. Prioli CERN 19 June 2019

  16. Ferromagnetic coupling - measurements • Same number of turns • Vrms= 0.1 – 0.2 V • 1 turn more/less over 754 • Vrms= 1.5 - 3 V M. Prioli CERN 19 June 2019

  17. Ferromagnetic coupling - measurements • Y axis in log scale! • Optimal frequency 500 Hz • Allows also to distinguish the origin of unbalance (number of turns or short) M. Prioli CERN 19 June 2019

  18. Conclusion • Additional QC methods were defined for the early detection of defects in the coils of the HiLumi corrector magnets • PJ method: sensitive and high voltage • Ferromagnetic coupling: very sensitive but low voltage • The PJ method, tuned for our small coils, indicated that • The quadrupole coils are free of insulation defects up to 400 V • The decapole and dodecapole coils have a VWL larger than 7 kV • In view of the series production, we consider • Using a commercial surge tester for the PJ method • Transforming a lab platform into an automated industrial test for the ferromagnetic coupling method M. Prioli CERN 19 June 2019

  19. Questions, remarks ? Thank you for you attention M. Prioli CERN 19 June 2019

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