Rockwell Automation T823X Trusted Power System - Manual (Page 17)

Trusted
TM
Power System T823X
Issue 9 Dec 08 PD-T823X 17
4.1.3. MCB discrimination
MCB discrimination studies should be carried out when designing the system power distribution.
Figure 8 Power pack (s) severe overload Current v Time
The graph above shows the response of a single power module to severe overloads. As the load is
increased the power supply protection mechanism operates and shuts down the output. It can be seen
that for a period of just in excess of 200mS the Power module can provide currents up to 115Amps or
380% of its stated maximum(115/31 = 3.8). This 200mS/380% can be extrapolated for additional
power supplies in order to perform MCB discrimination studies.
Power Unit(s) Overload Current Vs Time
0
50
100
150
200
250
300
0 20 40 60 80 100 120 140
Current / Amps
T
im
e
/
m
s
1 Power Unit
2 Power Units