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2
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4
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V
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P
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0 W
W
-23-
USA
Europe
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TEL:
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www.astec.com
Pins
The +Vin and -Vin input connection pins are
located as shown in Figure 1. AEH 24Vin con-
verters have a 2:1 input voltage range and can
accept 18-36 Vdc.
Care should be taken to avoid applying
reverse polarity to the input which can dam-
age the converter.
Input Characteristic
Fusing
The AEH 24Vin power modules have no
internal fuse. An external fuse must always
be employed!
To meet international safety
requirements, a 250 Volt rated fuse should be
used. If one of the input lines is connected to
chassis ground, then the fuse must be placed in
the other input line.
Standard safety agency regulations require
input fusing. Recommended fuse ratings for the
AEH 24Vin Series are shown in Table 1.
Input Reverse V
Input Reverse Voltage Protection
oltage Protection
Under installation and cabling conditions where
reverse polarity across the input may occur,
reverse polarity protection is recommended.
Protection can easily be provided as shown in
Figure 2. In both cases the diode rating is deter-
mined by the power of the converter. Diodes
should be rated as shown in Table1.
Placing the diode across the inputs rather
than in-line with the input offers an advan-
tage in that the diode only conducts in a
reverse polarity condition, which increases
circuit efficiency and thermal performance.
Input Undervoltage Protection
The AEH 24Vin series is protected against
undervoltage on the input. If the input voltage
drops below the acceptable range, the convert-
er will shut down. It will automatically restart
when the undervoltage condition is removed.
Input Filter
Input filters are included in the converters to
help achieve standard system emissions certifi-
cations. Some users however, may find that
additional input filtering is necessary. The AEH
24Vin 2.5Vout series has an internal switching
frequency of 180kHz so a high frequency
capacitor mounted close to the input terminals
produces the best results. To reduce reflected
noise, a capacitor can be added across the
input as shown in Figure 3, forming a
π filter. A
100
F/63V electrolytic capacitor is recom-
mended for C1.
-Vin
Case
CNT
-Vout
-Sense
Trim
+Sense
+Vout
+Vin
Fig.1 Pin Location
T
Table 1
able 1
Series
Fuse Rating(24Vin)
50W
10A
75W
15A
100W
20A
150W
30A
+Vin
-Vin
+Vin
-Vin
Fig.2 Reverse Polarity Protection Circuits