Lernkarten

Karten 14 Karten
Lernende 1 Lernende
Sprache English
Stufe Universität
Erstellt / Aktualisiert 04.05.2020 / 04.05.2020
Lizenzierung Keine Angabe
Weblink
Einbinden
0 Exakte Antworten 9 Text Antworten 5 Multiple Choice Antworten
Fenster schliessen

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.

Fenster schliessen
Lizenzierung: Keine Angabe

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

Fenster schliessen

What is clearance?

Lizenzierung: Keine Angabe
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

Fenster schliessen

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)

 

 

Fenster schliessen

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

Fenster schliessen

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)

Fenster schliessen

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 .
Fenster schliessen

On what is the aging of semiconductor mostly dependent?

Current load

Temperature