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Technical Information:
Basic Technical Data for Capacitors
Construction of Plastic Film Capacitors 
Dielectric 
Special Technical Subjects 


You are here: HomeTechnical InfoSelf-Inductance

Self-Inductance Depends on Construction Principle

Depending on the construction, an alternating current in the capacitor winding creates a more or less distinctive magnetic field which can be measured as inductance.

 

Old Type with High Self-Inductance

  The tape length of the
winding element determines
the value of the self-inductance

Modern WIMA Type

 

Modern plastic film capacitors are contacted over the whole end surface of the winding element. In this way the self-inductance of the winding element is short-circuited.

The self-inductance is reduced to the PCM (0.8 nH/mm) and the remaining length of the terminating wires (in case of SMD capacitors the distance between the soldering plates).

Average value for practical applications: inductance related to length = 0.8 nH/mm
Example: length of the terminating wires = 2 x 3 mm + PCM

   

WIMA MKS 02 / PCM 2.5 mm
Self-inductance L < 8 nH

WIMA SMD /Size code 1812
Self-inductance L < 6 nH

   
Increasing winding lengths in relation to the capacitance result in a large bonding area and guarantee low ESR values.

Thus plastic film capacitors stand out because of their HF properties which are the same as or better than those of ceramic capacitors of comparable size.