A new method of condition monitoring on electrical contact endurance of power switch
Prediction of the remaining electrical endurance of a power switch is important for the reliable performance of power switches. The erosion of contact material is one of the most important indexes for the electrical life of a contact. Previous methods of contact material life prediction are introduced. They mainly consider the relationship between erosion volume and current amplitude. A new idea is presented to diagnose the life of electrode material from the waveform characteristics of the make and break currents. LabVIEW is used to sample and store the current and voltage signals. Current waveforms, break/make current arc duration and contact resistance are discussed. As a result, the occurrence probability of fluctuating phenomena of the break current, contact resistance and make arc duration change with the number of contact operations. The break arc duration is determined by the break current.
Monitor of electrical endurance of vacuum circuit breaker's contacts
This paper discusses an approach to the monitoring of the electrical endurance of a vacuum circuit breaker's contacts, and gives the measurement circuit and signal processing method used.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.