Datasheet
QTD20.241
Q-Series
24V, 20A, DC INPUT
Mar 2012 / Rev. 1.2 DS-QTD20.241-EN
All parameters are specified at 24V, 20A, 600Vdc input, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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26. APPLICATION NOTES
26.1. REPETITIVE PULSE LOADING
Typically, a load current is not constant as it varies over time. For pulse load compatibility the following rules must be
met:
a) The pulse power demand must be below 125% of the nominal power.
b) The duration of the pulse power must be shorter than the allowed Bonus Time. (see output section)
c) The average (R.M.S.) output current must be below the specified continuous output current.
If the R.M.S. current is higher, the unit will respond with a thermal shut-down after a period of time. Use the
"Max. Duty Cycle Curve" (
Fig. 26-2) to check if the average output current is below the nominal current.
d) The duty cycle must be below 0.75.
e) For altitudes higher than 2000m reduce the pulse loading (15W/1000m) or the ambient temperature (5°C/1000m)
Fig. 26-1 Repetitive pulse loads, definitions Fig. 26-2 Max. Duty Cycle Curve
100%
P
PEAK
T
PEAK
P
0
T
0
max.
125%
125%100
0
0.2
0.4
0.6
0.75
Duty Cycle
105 110 115 120
P
PEAK
P
0
=
1
0
%
P
0
=
5
0
%
P
0
=
7
5
%
P
0
=
1
0
0
%
P
0
Base load (W)
P
PEAK
Pulse load (above 100%)
T
0
Duration between pulses (s)
T
PEAK
Pulse duration (s)
D
uty
C
ycle
T
0
=
T
peak
-
(D
uty
C
ycle
x T
peak
)
T
peak +
T
0
T
peak
D
uty
C
ycle
=
Utilizing the Max. Duty Cycle Curve:
Example to determine the repetition rate of pulses without dipping of the output voltage:
Parameters of application:
Pulse length of T
PEAK = 1s
Steady state load P
0=120W
(= 50% of I
RATED
)
Peak load P
PEAK = 600W
(= 125% of I
RATED
)
Determining the repetition rate:
1) make a vertical line at P
PEAK
= 125%
2) make a horizontal line where the vertical line crosses the P
0
= 50% curve
3) Read the Max. Duty Cycle from the Duty Cycle-axis (= 0.37)
4) Calculate the min. pause (base load) length T
0
:
D
uty
C
ycle
T
0
=
T
peak
-
(D
uty
C
ycle
x T
peak
)
=
0.37
1s
-
(0.37 x 1s)
=1.7s
5) Pulse length = 1s, min. pause length = 1.7s
6) Max. repetition rate = pulse length +pause length = 2.7s
More examples for pulse load compatibility:
P
PEAK
P
0
T
PEAK
T
0
P
PEAK
P
0
T
PEAK
T
0
600W 480W 1s >25s 600W 240W 0.1s >0.16s
600W 0W 1s >1.3s 600W 240W 1s >1.6s
540W 240W 1s > 0,75s 600W 240W 3s >4.9s
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