Study of Intrinsic Safety Basics and Testing Machines. Study of the Effect of Discharge Duration,Electrode Materials and Surface Conditions on the Minimum Igniting Currents.

摘要

The report presents the results of an investigation of the discharge duration power and current relation required for ignition. The current and power amplitude-discharge time curve flattened out over 3milliseconds (ms). It is concluded that discharges having at least 3ms of power maximum are required for reliable testing of the ignition limit for resistive circuits. Investigation of the effect of molten cathode on the discharge duration and igniting ability of the discharge showed that the surface tension of the liquid metal causes a very fast separation and consequently a much shorter discharge duration than the solid electrode would have. The minimum discharge voltage effect overrides the effects of the temperature of electrode,material,or atmosphere. Investigation of the effect of different surface layers on the discharge duration showed that the oxides and sulfates were of significantly duration than the 'clean'metal itself in most cases. The lowest ignition current was obtained with CdSO4coatings. Ignition was obtained with 0.7 A at 30 v,which is below the corresponding minimum igniting current obtained from the BASEEFA curve for circuits containing Cd,Zn,or Mg.