Beckhoff PS1011-2410-0000, Documentation, Page: 27 / 33

Application notes
PS1011-2410-0000 27 Version: 1.0
4 Application notes
4.1 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 input inrush current requirement of the pick-up coil is
several times higher than the steady-state current and usually exceeds the rated output current. 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. 14:
20A peak load (ohmic load) for 50ms output voltage drops from 24V to 14.9V;
50A peak load (ohmic load) for 5ms output voltage drops from 24V to 3.7V
Peak current voltage drops
Typically from 24V to 14.9V At 20A for 50ms, ohmic load
Typically from 24V to 7.1V At 50A for 2ms, ohmic load
Typically from 24V to 3.7V At 50A for 5ms, ohmic load
4.2 Back-feeding loads
Loads such as braking motors or inductors can feed back voltage to the power supply. This feature is also
known as back EMF. (
E lectro M agnetic F orce).
This power supply is stable and will not malfunction if a load is feeding back voltage to the power supply. It is
irrelevant whether the power supply is switched on or off.
The maximum permissible feed-back voltage is 35Vdc. The absorbing energy can be calculated according to
the large built-in output capacitor indicated in the
output data [
}
13] .