4. Power Pack Specifications Trusted Power System
14 Issue 11 Rockwell Automation Publication PD-T823X
Failure of an internal Power Pack fan results in shutdown of the output of the Power Pack.
4.1.2. Overcurrent Protection
The over-current protection limits the output current in the event of an overload. There are
two overload circumstances:
• If the load is increased steadily a single Power Pack compensates by derating the
voltage, hence at 40 A (the specification limit) the voltage is derated to 18.75 V. This
derated voltage is on the limit of the Trusted System Modules’ specification.
• Note: This gradual increase is not typical of a system fault.
• If 24 V is maintained over a rapid current rise, the over-current protection will trip
the power supply when 35 A is reached. This rapid increase is more typical of a fault
situation in a system.
4.1.3. MCB Discrimination
Miniature circuit breaker (MCB) discrimination studies should be carried out when designing
the system power distribution.
Figure 8 Power pack (s) Severe Overload Current v Time
0
50
100
150
200
250
300
0 20 40 60 80 100 120 140
Time / ms
Current / Amps
Power Unit(s) Overload Current Vs Time
1 Power
Unit
2 Power
Units
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