Difference between switching of motors and generators with vacuum technology

Abstract

Vacuum Circuit Breakers (VCBs) have been used for switching all kind of loads in industrial and distribution networks for more than 40 years. Due to their technological advancements and excellent advantages, the VCBs found their way into generator switching applications since 1994 and currently they are available for switching the generators rated up to 450 MVA. However it is observed that the switching phenomenon of the motors & generators are slightly different when VCBs are used. Especially in terms of switching motors with VCBs, in certain range of inductive currents, overvoltages might occur. These overvoltages can be mitigated using surge protection equipment like surge arresters & surge capacitors. On the other hand it has been widely asked if the same situation occurs during the switching of generators with VCBs. Do they also require surge arrester or surge capacitor for safe switching? The aim of this paper is to evaluate the switching phenomenon of motors that may cause overvoltages and analyze if the same phenomenon can be applied for generator switching. It is observed that the Vacuum Generator Circuit Breakers (VGCBs) don't require the surge protection to protect the generator since the VGCBs in this application will not generator any switching overvoltages.

Electromagnetic Field Analysis and Design of a Hermetic Interior Permanent Magnet Synchronous Motor with Helical-Grooved Self-Cooling Case for Unmanned Aerial Vehicles

“…For free molecular flow, the diffusion coefficient D m in the helical groove can be derived as follows. First, the throughput Q through helical groove is expressed as shown in the following equation [20].…”