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| DSH 612
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2 }! `3 n0 Q W | Destruction test on capacitors with segmented metallization
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| 60252-1(ed.1)
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Question:
, ]% \! K0 X# M, m' o' iTesting of motor capacitors with segmented metallization shows that during the destruction test in almost any cases for the capacitors with segmented metallization there occurs the interruption during the d.c. conditioning.+ S& e( [8 C. e2 K/ {+ h7 s+ }
During the d.c. conditioning of the destruction test usually there does not occur a short-circuit in the capacitor and consequently the d.c. voltage is increased to the maximum voltage value of 10 times the rated voltage and maintained for 5 minutes. During the following a.c. conditioning when applying an a.c. voltage of 1,3 times the rated voltage there is no current from the beginning. This means that during the d.c. conditioning all connections between the single segments of the metallization are interrupted like current fuses and that actually the interruption inside the capacitor occurs already during the d.c. conditioning.
, U* |# B$ O) Z! YNevertheless, during the a.c. conditioning, usually a very low current is still flowing trough the capacitor mainly due to the residual capacitance still present in the capacitance element.8 b! t# w1 c0 I/ \1 }' u
1) Is it allowed that an interruption of the capacitor occurs during the d.c. conditioning?3 k8 Z! G2 d( w/ y
2) When a capacitor can be considered as really interrupted?1 m7 U/ W3 D& Q
Decision:
/ R5 E* L2 D/ x- s q1) Following strictly the wording of sub-clause 2.16.3.2 it can not be judged as failure if the interruption of the capacitor occurs during the d.c. conditioning.9 k( _9 |; g: m7 ?" l y9 C
2) The capacitor can really be considered as interrupted when the finally obtained current during the a.c. conditioning is equal or lower than 1 % of the normal value when applying the test voltage to the capacitor with rated capacitance.
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