Rockwell Automation 1606-XLE240F-3 Power Supply Reference Manual - Manual (Page 17)

All parameters are specified at 24V, 2.5A, 230Vac input, 25ªC ambient and after a 5 minutes run-in time unless noted otherwise.
Rockwell Automation Publication 1606-RM031A-EN-P — April 2014 17
Bulletin 1606 Switched Mode Power Supplies
22. Application Notes
22.1. Peak Current Capability
Solenoids, contactors and pneumatic modules often have a steady state coil and a pick-up coil. The inrush current
demand of the pick-up coil is several times higher than the steady-state current and usually exceeds the nominal
output current (including the PowerBoost). The same situation applies when starting a capacitive load.
Branch circuits are often protected with circuit breakers or fuses. In case of a short or an overload in the branch circuit,
the fuse needs a certain amount of over-current to trip or to blow. The peak current capability ensures the safe
operation of subsequent circuit breakers.
Assuming the input voltage is turned on before such an event, the built-in large sized output capacitors inside the
power supply can deliver extra current. Discharging this capacitor causes a voltage dip on the output. The following
two examples show typical voltage dips:
Fig. 22-1 Peak load 10A for 50ms, typ. Fig. 22-2 Peak load 25A for 5ms, typ.
10ms/DIV
Output
Voltage
Output
Current
48V
0A
10A
34V
1ms/DIV
Output
Voltage
Output
Current
48V
0A
25A 28V
Peak load 10A (resistive) for 50ms
Output voltage dips from 48V to 34V. Peak load 25A (resistive) for 5ms
Output voltage dips from 48V to 28V.
22.2. Back-feeding Loads
Loads such as decelerating motors and inductors can feed voltage back to the power supply. This feature is also called
return voltage immunity or resistance against Back- E.M.F. (Electro Magnetic Force).
This power supply is resistant and does not show malfunctioning when a load feeds back voltage to the power supply.
It does not matter, whether the power supply is on or off.
The maximum allowed feed-back-voltage is 63Vdc. The absorbing energy can be calculated according to the built-in
large sized output capacitor which is specified in section 6.