Rockwell Automation 1606-XLP15B Power Supply Reference Manual - Manual (Page 17)

All parameters are specified at 12V, 1.3A, 230Vac input, 25°C ambient and after a 5 minutes run-in time.unless noted otherwise.
Rockwell Automation Publication 1606-RM020A-EN-P — March 2014 17
Bulletin 1606 Switched Mode Power Supplies
20. Application Notes
20.1. 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. 20-1 Peak loading with 2x the nominal
current for 50ms, typ.
Fig. 20-2 Peak loading with 5x the nominal
current for 5ms, typ.
Peak load 2.6A (resistive load) for 50ms
Output voltage dips from 12V to 7.8V. Peak load 6.5A (resistive load) for 5ms
Output voltage dips from 12V to 2V.
20.2. 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).
The maximum allowed feed back voltage is 25Vdc. The absorbing energy can be calculated according to the built-in
large sized output capacitor which is specified in section 6.
This power supply is resistant and does not show malfunction when a load feeds back voltage to the power supply.
It does not matter whether the power supply is on or off. However, please note that the output voltage can dip to
zero for approximately 200ms if the back-feed voltage is removed.