U.2.8
SEL-421 Relay User’s Guide Date Code 20090715
Installation
Shared Configuration Attributes
Figure 2.4 Standard Control Output Connection
See Control Outputs on page U.1.13 for complete standard control output
specifications.
Hybrid (High-Current-Interrupting) Control Outputs
The Hybrid (high-current-interrupting) control outputs are polarity dependent
and are capable of interrupting high-current, inductive loads. Hybrid control
outputs use an IGBT (Insulated Gate Bipolar Junction Transistor) in parallel
with a mechanical contact to interrupt (break) highly inductive dc currents.
The contacts can carry continuous current, while eliminating the need for heat
sinking and providing security against voltage transients.
With any hybrid output, break time varies according to the L/R (circuit
inductive/resistive) ratio. As the L/R ratio increases, the time needed to
interrupt the circuit fully increases also. The reason for this increased
interruption delay is that circuit current continues to flow through the output
MOV after the output deasserts, until all of the inductive energy dissipates.
Maximum dropout (break) time is 6 ms with a resistive load, the same as for
the Standard control outputs. The other ratings of these control outputs are
similar to the Standard control outputs, except that the Hybrid outputs can
break current as great as 10 A. Hybrid contact outputs have a maximum
voltage rating of 330 Vdc.
The maximum pickup time for the Hybrid control outputs is 6 ms. Figure 2.5
shows a representative connection for a Form A Hybrid control output on the
main board I/O terminals.
Figure 2.5 Hybrid Control Output Connection
See Section 1: Introduction and Specifications, for complete Hybrid control
output specifications.
Equipment damage can result from
connecting ac circuits to Hybrid
(high-current-interrupting) control
outputs. Do not connect ac circuits to
Hybrid control outputs. Use only dc
circuits with Hybrid control outputs.
Courtesy of NationalSwitchgear.com
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