Quench description by the characteristic time constants

The problem of a quench consequences of superconducting windings is considered. Inherent features of a quench behavior can be described by three characteristic time constants: (1) the normalization time t/sub n/ when normal zone would propagate over all winding volume provided transport current I/sub 0/ is kept constant, (2) the time of the current decay t/sub i/ provided the winding resistance R/sub 0/ is kept constant, and (3) the time of current decay t/sub n/ due to an external dump resistance R/sub e/. In a simple model where the normal zone velocities in longitudinal and transverse directions are proportional to the decaying current, a quench behavior (hot spot temperature, maximum internal voltage and stored energy evacuation efficiency) is analysed in dimensionless form depending upon the dimensionless time constants /spl tau//sub i/=t/sub i//t/sub n/ and /spl tau//sub e/=t/sub e//t/sub n/. It is shown that the active protection is efficient only if /spl tau//sub e/<1. In the absence of the active protection (/spl tau//sub e/=/spl infin/), for magnets with /spl tau//sub i/<1 the overheating is dangerous, while for those with /spl tau//sub i/>1 the internal voltages are dangerous. These results are confirmed by numerical examples which also show that the normalization time t/sub n/ is the most important parameter in the description of quench behavior.