Data Sheet

QT20.241, QT20.241-C1
Q-Series
24V, 20A, THREE PHASE INPUT
Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
22.2. PEAK CURRENT CAPABILITY
The power supply 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 BonusPower
®
). 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 over-current 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 two examples show typical voltage dips:
Fig. 22-3 Peak load with 2x the nominal
current for 50ms, typ.
Fig. 22-4 Peak load with 4x the nominal
current for 5ms, typ.
20ms/DIV
Output
Voltage
Output
Current
24V
0A
40A
18V
2ms/DIV
Output
Voltage
Output
Current
24V
0A
80A
16.5V
40A Peak load (resistive) for 50ms
Output voltage dips from 24V to 18V.
80A Peak load (resistive) for 5ms
Output voltage dips from 24V to 16.5V.
Please note: The DC-OK relay triggers when the voltage dips more than 10% for longer than 1ms.
Peak current voltage dips typ. from 24V to 18V At 40A for 50ms, resistive load
typ. from 24V to 19V At 80A for 2ms, resistive load
typ. from 24V to 16.5V At 80A for 5ms, resistive load
22.3. EXTERNAL INPUT PROTECTION
The unit is tested and approved for branch circuits up to 15A (U.S.A.) and 16A (IEC). 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 3A C-Characteristic breaker should be chosen.
22/27
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and after
a 5 minutes run-in time unless otherwise noted.
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