G.M. International D1073S Instruction Manual page 8

Power Dissipation of D1073 Isolators
Section "Technical Data" of D1073 isolator specifies the current consumption (maximum current from the nominal power supply, typical 24 Vdc, in normal operation); this data serves to
dimension the current rating of the power supply unit. Section "Technical Data" indicates also the maximum power consumption (maximum power required from the power supply in the
worst (abnormal) operating conditions like for example supply voltage at 30 Vdc, short circuit on the outputs and on the inputs terminals.
The power dissipated Pd inside the enclosure for analog signal isolators is: Pd = Current Consumption (A) * Supply Voltage (V) - Power Dissipated into the input/output loads
Analog signal isolators have higher dissipation than digital signal isolators. In analog signal isolators each transmitter requires and dissipates 15 V * 0.02 A = 0.3 W. Usually the loads
outside the isolator dissipate 1/3 of the total power used. Isolators are not running at the maximum current all at the same time, the average power consumption of a multitude of isolators
can be considered to be only 70 % of the value obtained from the section "Technical Data". Considering the 1/3 load power and the 70 % above discussed, the power effectively
dissipated internally by the isolators can therefore become ½ of the actual power delivered by the power supply. Digital barriers dissipate all the supply power inside the enclosure
consequently the total power dissipation into a cabinet, with mixed analog and digital barriers, is determined by the number of channels more than by the number of isolator enclosures.
The following tables give advises for the DIN rail orientation (vertical or horizontal) of the barriers mounting, D1073S (single channel) isolators, installed on DIN rail, bus or custom board
assembly.
A) Cabinet with Natural Ventilation
Maximum recommended ambient temperature in °C depending on barrier type and installation method:
Single unit
Type of Isolator
Installation
Any orientation
D1073S 60°C
B) Cabinet with Forced Ventilation
Maximum recommended ambient temperature in °C depending on barrier type and installation method:
Single unit
Type of Isolator
Installation
Any orientation
D1073S 60°C
8
D1073 - SIL 2 Temperature Signal Converter and Trip Amplifiers
Installation in Cabinet
Installation of Multiple units with DIN-rail Bus
Vertical Horizontal
30°C 35°C
Installation of Multiple units with DIN-rail Bus
Vertical Horizontal
40°C 45°C
Installation on Custom Boards
Vertical Horizontal
35°C 40°C
Installation on Custom Boards
Vertical Horizontal
45°C 50°C
G.M. International ISM0019-13