REV. AUG 26, 2005
Page
5 of 18
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FC Filter Series
5A, 10A, 20A Filter Data Sheet
DC Current Ratings:
FC filters are rated for 5.0, 10.0, and 20.0 amperes DC at up to +60° C. ambient temperature with 400 LFM of forced air across
the module surface, or with the case temperature otherwise held to a maximum of +100° C. With no forced air and no additional
cooling, the same modules are rated for 3.5, 6.5, and 13 amperes maximum.
SAFETY CONSIDERATIONS
Isolation:
The FC Series EMI filters have 1500 Volt DC isolation from input or output to ground, but no isolation from input to output. The
output voltage is the input voltage.
Fusing:
These filters have no external fuse. An external fuse must always be employed. In general, a 250 volt rated fuse must be used
to meet international safety requirements. The fuse value should be selected to be greater than the maximum input current of the
filter, which occurs at the minimum input voltage of the modules being powered through the filter. Both input traces and the
chassis ground trace (if used) must be capable of conducting a current of 1.5 times the value of the fuse without opening. If one
of the input lines is connected to chassis ground, then the fuse must be in the other input line.
Case Grounding:
The FC Series filters have a non-metallic case. It cannot be grounded. Each filter has a ground pin which must be connected,
with as low an impedance as possible, to chassis ground in order for the filter to function properly.
INPUT SHUTDOWN PIN
Many DC-DC converter modules have an input “shutdown”, or “control” or “ON/OFF” pin. In most cases, the reference or return
for this pin is the negative input pin of the module. When using such a system with an EMI filter module, the shutdown return
must be made directly to the pin of the module, which is the output of the filter, and not at the input of the filter. This requires
either an optical coupler or a relay, or other fully isolated device to control the module. There must not be any path for DC current
to bypass the module, or its filtering characteristics will be severely compromised.
In order to operate without the internal common mode inductors magnetically saturating, the positive leg and negative leg
currents in the filter must exactly equal. Even a small imbalance, as small as 10 ma, can create saturation of the inductors.
When this happens, they no longer function as filter elements.