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Thermal Characteristics
The amplifiers are specified to operate at a 45° C ambient. This is not a maximum safe
operating specification. There are no parts in the amplifier that can not operate at a 60° C
temperature. The absolute maximum temperatures that the amplifier can operate at are
determined by thermal switches on the bridge switch power devices (IGBT's) and on the shunt
loads. These thermal switches open and disable the amplifier at 85° C.
At temperatures above 45° C, the amplifiers ability to produce its continuous rating is impaired
by the heat rise from the ambient temperature, and the amplifier will thermally shut down once
the 85° condition is sensed at either the bridge or the shunt load.
A guideline for enclosures would be to assume that the amplifiers thermal losses are equal to
16 times the continuous 50 watts. The 50 watts is required for the logic supplies.
Example
50 Amp
*
16 + 50 = 800 watts
This would be the amplifier losses.
If the application is causing bus pumping, and the shunts are being used, the thermal rise from
the shunts is restricted to 85° C and the actual power rating of the shunt load. The thermal
rise of amplifiers with internal shunts could equal the amplifier thermal losses.
