High Current Simulation Research Articles

Modeling MOS snapback and parasitic bipolar action for circuit-level ESD and high-current simulations

The design and optimization of ESD protection circuits is greatly enhanced by the ability to perform circuit-level simulations of the protection circuits and the I/O buffers. Most available simulators do not cover the high current region of the circuit operation, but still enable an approximate analysis to be made of the behaviour under ESD conditions. In this article, a description of the behaviour of the MOS device in the high current regime is presented together with the model equations governing that behaviour. The equations have been implemented into a SPICE circuit simulator, and the experimental and simulation results are given. A simple parameter extraction methodology is presented that uses the terminal currents from a single MOS DC I-V curve to obtain all the MOS and bipolar parameters required for the model.

Simulation of gas flow phenomena in high-voltage self-blast circuit breakers at heavy fault current interruption

CFD (computational fluid dynamics) calculations for high- and low-current arcs in an interrupter of the self-blast type have been performed. The high-current simulation provides information about the mixing process of the hot PTFE cloud with the cold SF/sub 6/ which is difficult to access for measurement. In addition, it yields the gas state inside the pressure chamber when the fault current approaches its current zero. Depending on the arcing time, fault current and interrupter geometry blow temperatures of up to 2000 K with a PTFE mass fraction of up to 10% have been found. The low-current simulation performed for this blow temperature gives detailed information about the arc behaviour in the time immediately before current zero. Special attention has been paid to the flow phenomena in the expanding nozzle region. Due to the interaction of the supersonic flow with the obtuse arcing contact and the nozzle geometry, a complex flow structure with a shock Is established. This has been simulated for low-current arcs in an extinguishing flow with boundary conditions as obtained from the high-current simulation.