Difference between revisions of "Testing Procedures for Power Engineering"
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===13.4.1 Metallurgical Analysis=== | ===13.4.1 Metallurgical Analysis=== | ||
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| + | The main characteristic for the appraisal of contact materials for power engineering is the optical evaluation of their microstructure in a metallographic mount. This provides a picture of the internal structure of the materials. It allows detecting structural in-homogeneity, grain boundary enrichments, cracks, material separations, or defects in the brazing interface. The metallographic view is however limited to the one two-dimensional plain in which the mounting cut was made. | ||
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| + | Fig. 13.11 shows the microstructure of a Ag/CdO contact material after being affected by electrical arcing. In the lower part the starting material structure is visible. In the upper part the de-mixing of the composite material through the effects of the switching arc is clearly demonstrated. This “switching structure” shows in certain areas depletion of metal oxide which increases the probability of contact welding during subsequenbt make operations. Additional analysis by X-ray probing in a scanning electron microscope (SEM) allows the micro analysis of the elements present in the contact surface region. | ||
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| + | Fig. 13.11: | ||
| + | Microstructure of a powder | ||
| + | metallurgical Ag/CdO material after | ||
| + | being affected by intense electrical | ||
| + | arcing. | ||
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| + | ===13.4.2 Testing According to IEC/EN=== | ||
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| + | ====13.4.2.1 Electrical Life==== | ||
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| + | The electrical life of contactors, motor switches, and auxiliary current switches used in power engineering is classified into use categories which are shown in table 13.1: | ||
Revision as of 16:27, 16 January 2014
13.4.1 Metallurgical Analysis
The main characteristic for the appraisal of contact materials for power engineering is the optical evaluation of their microstructure in a metallographic mount. This provides a picture of the internal structure of the materials. It allows detecting structural in-homogeneity, grain boundary enrichments, cracks, material separations, or defects in the brazing interface. The metallographic view is however limited to the one two-dimensional plain in which the mounting cut was made.
Fig. 13.11 shows the microstructure of a Ag/CdO contact material after being affected by electrical arcing. In the lower part the starting material structure is visible. In the upper part the de-mixing of the composite material through the effects of the switching arc is clearly demonstrated. This “switching structure” shows in certain areas depletion of metal oxide which increases the probability of contact welding during subsequenbt make operations. Additional analysis by X-ray probing in a scanning electron microscope (SEM) allows the micro analysis of the elements present in the contact surface region.
Fig. 13.11: Microstructure of a powder metallurgical Ag/CdO material after being affected by intense electrical arcing.
13.4.2 Testing According to IEC/EN
13.4.2.1 Electrical Life
The electrical life of contactors, motor switches, and auxiliary current switches used in power engineering is classified into use categories which are shown in table 13.1:
