Sel 551 - Page 28

2.8
SEL-551 Relay Instruction Manual Date Code 20110408
Installation
Rear-Panel Connections
Plug-In Connector
Improvements
Result in Part
Number Changes
The current transformer shorting connector (for current channel inputs IA, IB,
IC, and IN) has been made more robust. This improvement makes the new
connector design incompatible with the old design. Thus, presently
constructed Connectorized SEL-551 Relays with this improved connector
have a new part number (partial part numbers shown):
The respective wiring harness part numbers for these old and new
Connectorized SEL-551 Relays are (partial part numbers shown):
The other connectors on the Connectorized SEL-551 rear panel (power input,
output contacts, etc.) are the same for the old or new model. Only the current
transformer shorting connector has changed.
Figure 2.8 shows the rear panel for new model 05510W. This figure can also
be used as a reference for old model 05510J. All terminal labeling/numbering
remains the same.
High-Current
Interrupting Output
Contacts
Relays with plug-in connectors as shown in Figure 2.8 contain output contacts
capable of interrupting load current up to 10 amps. The output contacts
contain internal contact arc suppressors that protect the output contacts from
damage due to electrical arcs. Apply these output contacts to very sensitive,
high speed loads or to heavy resistive or inductive loads up to their interrupt
rating. No special connections are required to use the integral arc suppressors;
however, the output contacts are polarity dependent as mentioned previously
in this section.
The arc suppressors in the SEL-551 are different from the SEL-9501 Contact
Arc Suppressor. The high-current interrupting output contacts in the SEL-551
have the same interrupt rating as the SEL-9501, but typically have less than
1 µA of leakage current, and exhibit virtually none of the let-through exhibited
by the SEL-9501. See SEL Application Guide 97-23, SEL-9501 Contact Arc
Suppressor Application Guidelines for more information regarding the
SEL-9501 and the let-through phenomenon. A single SEL-9501 can
theoretically be used to protect multiple contacts simultaneously, but the arc
suppressors inside the SEL-551 protect only the SEL-551 output contacts.
The high-current interrupting output contacts in the SEL-551 are guaranteed
to not turn on or latch up regardless of the rate of rise of voltage across the
protected contacts (i.e., these arc suppressors do not exhibit SCR type latch up
because they do not use SCRs).
Old New
05510J 05510W
Old New
W05510J WA05510W
IMPORTANT: Improvements in
Connectorized (Plug-In Connectors)
SEL-551 Relay Result in Part Number
Changes