Rockwell Automation 1606-XLP60BQT Power Supply Reference Manual - Manual (Page 17)

All parameters are specified at 12V, 4.5A, 230Vac input, 25°C ambient and after a 5 minutes run-in time unless noted otherwise.
Rockwell Automation Publication 1606-RM016A-EN-P — February 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. The same situation applies when starting a motor or switching-on a capacitive load.
In many cases, the peak current capability also ensures a safe operation of subsequent circuit breakers. Branch circuits
are often protected with circuit breakers or fuses. In case of a short or an overload in a branch circuit, the fuse needs a
certain amount of over-current to trip or to blow.
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 examples
below 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.
10ms/DIV
Output
Voltage
Output
Current
12V
0A
9A
7V
1ms/DIV
Output
Voltage
Output
Current
12V
0A
22.5A
3.2V
Peak load 9A (resistive load) for 50ms
Output voltage dips from 12V to 7V. Peak load 22.5A (resistive load) for 5ms
Output voltage dips from 12V to 3.7V.
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).
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 25Vdc. The absorbing energy can be calculated according to the built-in
large sized output capacitor which is specified in section 5.