Application notes
PS3031-2440-0000
33
Version: 1.0
4.2
Peak current capability
The device can deliver peak currents (for up to several milliseconds) that are higher than the specified short-
term currents.
This helps when starting loads with high current intensity. Magnetic coils, contactors and pneumatic modules
often have a stationary coil and a pick-up coil. The inrush current requirement of the pick-up coil is several
times higher than the stationary current and usually exceeds the rated output current (including extra power).
The situation is exactly the same when starting a capacitive load.
The peak current capability also ensures safe operation of downstream circuit breakers of load circuits. The
load circuits are often individually fused with circuit breakers or fuses. In the event of a short circuit or
overload in a circuit, the fuse or circuit breaker needs a certain amount of overcurrent to open in time. This
prevents a voltage drop in adjacent circuits.
The additional current (peak current) is supplied by the power converter and the built-in large-size output
capacitors of the power supply. The capacitors are discharged during such an event, which leads to a
voltage drop at the output. The following two examples show typical voltage drops for ohmic loads:
Fig. 22: 80 A peak current for 50 ms, typ. (2 x nominal current), 200 A peak current for 5 ms, typ. (5x nominal
current)
Control of DC-OK relay
Please note: The DC-OK relay is activated if the voltage drops by more than 10% for more than
1 ms.
Peak current voltage drops
Typically from 24 V to 20 V
At 80 A for 50 ms, ohmic load
Typically from 24 V to 12 V
At 200 A for 2 ms, ohmic load
Typically from 24 V to 12 V
At 200 A for 5 ms, ohmic load
