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Erstellt / Aktualisiert 04.05.2020 / 04.05.2020
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0 Exakte Antworten 9 Text Antworten 5 Multiple Choice Antworten
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Why do we need low inductances ?

The lower the inductance in the commutation path, the less overvoltage occurs during the switching transients (reduces stress on components).

Housings of high speed switching devices should allow a very thight mounting of the commutation capacitors.

The getting low inductive circuits the commutation circuit should be the smallest loop.

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What is the simplified relation for the inductance of the traces?

(1x h/w) * nh / cm

(5x h/w) * nh / cm

(8x h/w) * nh / cm

(2x h/w) * nh / cm

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What is clearance?

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The shortest path between two conductive parts (or bounding surface) measured through air

The shortet path between two conductive pats (or bounding surface) measured along the surface of the insulation

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Name all 5 categories of insulation standards.

  • functional insulation --> necessary for proper functioning of the device over lifetime. It is no safety protection!


  • basic insulation --> provides basic protection against electric shock with a single level. Has no minimum thickness specification for solid insulation. Safety is provided by second level protection.


  • supplementary insulation--> used in connection with basic insulation to provide second level of protection. A single layer of insulating material must have a minimum thickness of 0.4 mm to be considered as supplementary insulation.


  • double insulation --> two level system consisting of basic + suplementary insulation


  • reinforced insulation--> single insulation system equivalent to double insulation. Requires minimum thicknes of 0.4mm for use in single layer. (recommends to use 2 sheets of prepregs)



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what is the working voltage?

Highest voltage to which the insulation or the component can be used when the equipment is operating under conditions of normal use

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what is the comparative tracking index?

comparatie tracking index (CTI) is used to measure the electrical breakdown properties of an insulating magerial . Materials are classified in four groups (FR4 baced PCBs are group 2)

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Explain the pollution degrees 1 - 4

  • pollution degree 1 --> no pollution or only dry. Pollution has no influence (sealed)


  • 2--> nonconductive pollution occurs. occasionally a temporary conductivity caused by condensation must be expected (household device)


  • 3--> conductive pollution occurs, or dry, non conductive pollution that becomes conductive due to expected condensation (industrial environment)


  • 4--> pollution generates persistent conductivity caused by conductive dust, rain, snow. Steps are taken to control pollution degree by design features .
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On what is the aging of semiconductor mostly dependent?

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