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.
Effects of Equipment Dimensions on Liquid Mixing Time of Bubble Column with Draft Tube
The liquid mixing time of a bubble column with a draft tube is experimentally studied. The diameter and height of the column, the diameter and length of the draft tube, and the mode of sparging gas were changed and the liquid mixing time was measured.The lengths of bottom and top clearances have significant effects on the liquid mixing time. The liquid mixing time increases with increasing column aspect ratio of height to diameter. The liquid mixing time of the bubble column with a draft tube is longer than that of a standard bubble column when the column aspect ratio is relatively high. The liquid mixing time has a minimum when the diameter ratio of draft tube to column is 0.5 to 0.6. These effects of equipment dimensions are expressed by an equation. In the experiment using different solutions, the liquid mixing time becomes shorter with increasing liquid surface tension, or with increasing liquid viscosity.