QS3.241

Q-Series

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.

Branch circuits are often protected with circuit breakers or fuses. In case of a short or an overload in the branch circuit,

the fuse 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

two examples show typical voltage dips:

Fig. 23-3 Peak load with 2x the nominal

current for 50ms, typ.

Fig. 23-4 Peak load with 4x the nominal

current for 5ms, typ.

Output

Voltage

Output

Current

10ms/DIV

24V

0A

6.8A

18.5V

Output

Voltage

Output

Current

1ms/DIV

24V

0A

13.5A

7.5V

Peak load 6.8A (resistive) for 50ms

Output voltage dips from 24V to 18.5V.

Peak load 13.5A (resistive) for 5ms

Output voltage dips from 24V to 7.5V.

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 35Vdc. The absorbing energy can be calculated according to the built-in

large sized output capacitor which is specified in chapter 6.

The unit is tested and approved for branch circuits up to 20A. An external protection is only required if the supplying

branch has an ampacity greater than this. Check also local codes and local requirements. In some countries local

regulations might apply.

If an external fuse is necessary or utilized, minimum requirements need to be considered to avoid nuisance tripping of

the circuit breaker. A minimum value of 6A B- or 6A C-Characteristic breaker should be used

Nov. 2011 / Rev. 2.1 DS-QS3.241-EN

All parameters are specified at 24V, 3.4A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.

www.pulspower.com Phone +49 89 9278 0

Germany

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