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-23-
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www.astec.com
input-to-output 1500VDC isolation is an opera-
tional insulation. The DC/DC power module
should be installed in end-use equipment, in
compliance with the requirements of the ulti-
mate application, and is intended to be supplied
by an isolated secondary circuit. When the sup-
ply to the DC/DC power module meets all the
requirements for SELV(<60Vdc), the output is
considered to remain within SELV limits (level
3). If connected to a 60Vdc power system, dou-
ble or reinforced insulation must be provided in
the power supply that isolates the input from
any hazardous voltages, including the ac
mains. One Vin pin and one Vout pin are to be
grounded or both the input and output pins are
to be kept floating. Single fault testing in the
power supply must be performed in combina-
tion with the DC/DC power module to demon-
strate that the output meets the requirement for
SELV. The input pins of the module are not
operator accessible.
Note: Do not ground either of the input pins of
the module, without grounding one of the output
pins. This may allow a non-SELV voltage to
appear between the output pin and ground.
Case Grounding
For proper operation of the module, the case or
baseplate of the AEH module does not require
a connection to a chassis ground. If the AEH
module is not in a metallic enclosure in a sys-
tem, it may be advisable to directly ground the
case to reduce electric field emissions. Leaving
the case floating can help to reduce magnetic
field radiation from common mode noise cur-
rents. If the case has to be grounded for safety
or other reasons, an inductor can be connected
to chassis at DC and AC line frequencies, but
be left floating at switching frequencies. Under
this condition, the safety requirements are met
and the emissions are minimized.
Output Characteristics
Minimum Load Requirement
There is no minimum load required for the AEH
series modules.
Remote Sensing
The AEH converter can remotely sense both
lines of its output which moves the effective out-
put voltage regulation point from the output of
the unit to the point of connection of the remote
sense pins. This feature automatically adjusts
the real output voltage of the AEH in order to
compensate for voltage drops in distribution
and maintain a regulated voltage at the point of
load.
When the converter is supporting loads far
away, or is used with undersized cabling, sig-
nificant voltage drop can occur at the load. The
best defense against such drops is to locate the
load close to the converter and to ensure ade-
quately sized cabling is used. When this is not
possible, the converter can compensate for a
drop of up to 0.5V, through use of the sense
leads.
When used, the + and - Sense leads should be
connected from the converter to the point of
load as shown in Figure 9 using twisted pair
wire. The converter will then regulate its output
voltage at the point where the leads are con-
nected. Care should be taken not to reverse the
sense leads. If reversed, the converter will trig-
ger OVP protection and turn off. When not
+Vout
-Vout
Load
+Sense
-Sense
Twisted Pair
+S
-S
Fig.9 Sense Connections