Ampacity-derating may be mitigated by the use of purpose-designed intumescent or mechanically / electronically activated " windows " that permit heat venting.
32.
However, at the lower end of a loudspeaker's usable frequency range, its power handling might necessarily be derated because of mechanical excursion limits.
33.
For some capacitor types therefore the IEC standard specifies a " temperature derated voltage " for a higher temperature, the " category voltage U C ".
34.
Derating is necessary because multiple conductors carrying full-load power generate heat that may exceed the normal insulation temperature rating . ( NEC 310.16)
35.
It was a derated version of the 32 cubic inch engine block used at that time on the OMC Evinrude 25 / 30 / 35 hp outboards.
36.
For some capacitor types therefore the IEC standard specify a second " temperature derated voltage " for a higher temperature range, the " category voltage ".
37.
For some capacitor types therefore the IEC standard specify a " temperature derated voltage " for a higher temperature, the " category voltage U C ".
38.
Derating can also be used to provide a safety margin for transient voltages or currents ( spikes ) that exceed normal operation, or simply to prolong life.
39.
Tantalum capacitors, which are exposed to surge, peak or pulse currents should be used with a voltage derating up to 70 % in highly inductive circuits.
40.
For instance, a resistor may have a threshold temperature of 70 �C and a maximum temperature of 155 �C, between which it exhibits a thermal derating.
