Rockwell Automation 1606-XLP50E Power Supply Reference Manual - Manual (Page 17)

All parameters are specified at 24V, 2.1A, 230Vac input, 25ªC ambient and after a 5 minutes run-in time unless noted otherwise.
Rockwell Automation Publication 1606-RM034A-EN-P — March 2014 17
Bulletin 1606 Switched Mode Power Supplies
26. Application Notes
26.1. Peak Current Capability
Solenoids, contactors and pneumatic modules often have a steady state (sealed) coil and a pick-up coil. The inrush
current demand of the pick-up coil is several times higher than the steady state curre nt and usually exceeds the
nominal output current. 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 protective device (fuse, circuit breaker) 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
examples show typical voltage dips:
Fig. 26-1 Peak load 4.2A for 50ms, typ. Fig. 26-2 Peak load 10.5A for 5ms, typ.
10ms/DIV
Output
Voltage
Output
Current
24.0V
0A
4.2A
16V
1ms/DIV
Ou
tpu
t
V o
ltag
e
Output
Current
24.0V
0A
10.5A
10.5V
Peak load 4.2A (resistive) for 50ms
Output voltage dips from 24V to 16V.
Peak load 10.5A (resistive) for 5ms
Output voltage dips from 24V to 10.5V.
26.2. Back-feeding Loads
Loads such as decelerating motors and inductors can feed voltag e back to the power supply. This feature is also called
return voltage immunity or resistance against Back-EMF (Electro Magnetic Force).
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.
The maximum allowed feed back voltage is 35Vdc. The absorbing energy can be calculated according to the built-in
large sized output capacitor which is specified in section 10.