ABB Ltd

About: ABB Ltd is a company organization based out in Zurich, Switzerland. It is known for research contribution in the topics: Voltage & Signal. The organization has 6222 authors who have published 6852 publications receiving 83994 citations.

Effective ionization rate in nitrogen–oxygen mixtures

Abstract: The effective Townsend ionization coefficient in nitrogen–oxygen mixtures at various pressures is determined. In addition to the commonly accepted difference of the ionization and the attachment coefficients, α and η, respectively, the electron detachment from the negative ions created by the avalanche itself is taken into account. This leads to non-zero effective ionization rate below the threshold field corresponding to α − η = 0.

Self-consistent radiation based modelling of electric arcs: I. Efficient radiation approximations

Abstract: We perform a systematic investigation of methods for including radiation transport in arc simulations by analysing both various ways of solving the radiation transfer equation and methods for averaging the absorption coefficient over frequency. We show that the discrete ordinate method (DOM) and the P1 approximation can be used to produce good results: DOM being slightly more accurate and P1 being faster. Furthermore, we demonstrate that it is possible to start from the full absorption spectrum and produce band-averaged absorption coefficients with sufficient accuracy, if the frequencies are grouped not only based on frequency but also based on their magnitude. This makes it possible to introduce radiation transport in arc simulations in a systematic manner, with full control of accuracy. In a follow-up paper, part II, we apply our results to the simulation of several switching arcs, demonstrating the feasibility of self-consistent arc simulations for switching applications.

Time synchronization in computer network

Abstract: A method for improved Network Time Protocol time synchronization in a computer network (1) where the computer network comprises a time client (2) and a timeserver (3). To eliminate network access errors at the client side, the actual time of leaving is stored in the time client (2) as a special time stamp (T11) and later substituted for T1 in the calculations. To eliminate network access errors at the server side, the time request packet is duplicated and returned twice, the second time containing the time stamp when the first packet left the server (T31). To eliminate network transversal jitter when using a switched network, a packet with a multicast is used and the time stamp (T11) is taken when the time request packet is reflected back from the switch and (T31) is taken when the reply packet is reflected back from the switch.