Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 293 / 734

Date Code 20010625 Inputs, Outputs, Timers, and Other Control Logic 7-41
SEL-311L Instruction Manual
DWG: M311L070
SEL-311L SEL-311L
Figure 7.30: Typical Two-Terminal Application With Tapped Load
Use of High-Speed Contacts OUT201–OUT206 With Fast, Sensitive Loads
High-speed contacts OUT201–OUT206 are intended for use as high-speed trip contacts.
OUT201–OUT206 can also be used with sensitive, fast contact inputs, such as might be found on
some communications gear.
Load sensitivity is described by minimum assertion voltage (per unit of nominal dc control
voltage), minimum pickup time (milliseconds to energize the load at nominal control voltage),
and load resistance. Use OUT201–OUT206 with any load that satisfies Equation 7.1 and does
not assert below 20% of nominal dc control voltage.
pu L
T • 500 R
≤
Equation 7.1
where:
R
L
is the load resistance in k
8
.
T
pu
is the minimum load response time, in milliseconds.
For example, a 125 V contact input on an SEL-311L Relay does not assert below half the
nominal dc control voltage. The input draws 4 mA at nominal voltage, so R
L
= 125 V / 4 mA =
31 k
8
. With the debounce timer set to 2 ms, this input easily satisfies Equation 7.1, with a
safety factor of over 30.
1000 31
2 • 500 31
≤
≤