Date Code 20011026
Interface Board Specifications
I-9
SEL-321/321-1 Instruction Manual
I
NTERFACE
B
OARD
5 (8 O
UTPUTS
, 8 I
NPUTS
) - S
CREW
-T
ERMINAL
Optoisolated Inputs
All eight control inputs are standard, fixed-voltage, dry optoisolated inputs, and are not polarity
dependent. The nominal rated control voltage of 24, 48, 125, or 250 Vdc must be specified when
ordering. To assert an input, apply control voltage to the terminals assigned to that input. Each
input is individually isolated, and a terminal pair is brought out for each input. There are no
internal connections between inputs. The inputs will assert within 2 ms and draw approximately
4 mA of current at nominal voltage. For further information, see
General Specifications
in
Section 2
.
Output Contacts
30 A make
6 A carry
10 A interrupt for L/R<0.04 seconds at 125 Vdc
10 A interrupt for L/R<0.02 seconds at 250 Vdc
Closing (open-to-close for both “a” or “b” contacts): 200
m
s
Opening (close-to-open for both “a” or “b” contacts): typically 1/2-cycle
Interface board 5 provides eight output contacts. These eight
Fast High Current Interrupting
dry output contacts can interrupt 10 A of inductive current with an L/R <0.04 seconds. At 250
Vdc, they will interrupt 10 A of inductive current for an L/R <0.02 seconds. They operate (close
for “a” contacts and open for “b” contacts) in less than 10
m
s (.00001 seconds). Due to relay
capabilities the outputs of the SEL-321 Relay are specified at 200
m
s (.0002 seconds).
The output contacts may be configured as either “a” or “b” contacts with solder jumpers.
Figure I.15 show the locations of the jumpers and explain the jumper positions. Contacts are
factory-configured as “a” contacts (except the alarm contact which is “b”).
Short transient inrush current may flow when a switch that is in series with the contact is closed,
and the Interface 5 contact is open. This transient will not energize the circuit used in typical
applications. Trip and Close coils and standard auxiliary relays will not pick up; however, an
extremely sensitive digital input or light-duty, high-speed auxiliary may pick up for this
condition. The transient occurs when the capacitance of the output contact circuitry is charged.
A third terminal for each contact provides a path for charging the capacitance when the circuit is
open. See Figure I.12 and Figure I.13.
Figure I.14 shows some possible connections for this third terminal that will eliminate the
possibility of transients when closing a switch. Circuit load is not shown. In general, the third
terminal must be connected to the dc rail that is on the same side as the open switch condition. If
an open switch may exist on either side of the output contact, only one condition may be
considered. Two open switches (one on each side of the contact) defeat the charge circuit.
The Interface 5 contact outputs are
not
polarity dependent.
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