Rockwell Automation Publication 1606-RM110A-EN-P - July 2020
25
Redundancy Power Supply - 24V, 10 A, 240 W, Single-phase Input
Applications Notes
Peak Current Capability
The unit can deliver peak currents (up to several milliseconds) which are higher
than the specified short term currents.
This helps to start current demanding loads. 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.
The peak current capability also ensures the safe operation of subsequent
circuit breakers of load circuits. The load branches are often individually
protected with circuit breakers or fuses. In case of a short or an overload in one
branch circuit, the fuse or circuit breaker need a certain amount of overcurrent
to open in a timely manner. This avoids voltage loss in adjacent circuits.
The extra current (peak current) is supplied by the power converter and the
built-in large sized output capacitors of the power supply. The capacitors get
discharged during such an event, which causes a voltage dip on the output. The
following three examples show typical voltage dips for resistive loads:
Figure 30 - 20 A Peak Current for 50 ms, Typ
(2x the Nominal Current)
Figure 31 - 50 A Peak Current for 5 ms, Typ
(5x the Nominal Current)
Figure 32 - 30 A Peak Current for 12 ms, Typ
(3x the Nominal Current)
Output
Voltage
24V
10ms/DIV
Output
Current
0A
20A
17V
Output
Voltage
24V
Output
Current
1ms/DIV
0A
50A
15.5V
24V
10ms/DIV
Output Voltage
Output Current
0A
12ms
30A
10.5V
Peak Current Voltage Dips
(1)
Typ
from 24V to 17V
At 20 A for 50 ms, resistive load
Typ
from 24V to 19V
At 50 A for 2 ms, resistive load
Typ
from 24V to 15.5V
At 50 A for 5 ms, resistive load
(1)
The DC OK relay triggers when the voltage dips more than 10% for longer than 1 ms.