18
This standard applies to all parts of a circuit breaker that
function during normal operation. It does not apply to other
parts, such as overcurrent tripping devices that function
only during infrequent abnormal circuit conditions.
Table 18.1 Repetitive duty and normal maintenance
(from ANSI C37.16 Table 5)
À Servicing consists of adjusting, cleaning, lubricating, tightening, etc., as recommended
by the manufacturer. When current is interrupted, dressing of contacts may be
r
equired as well. The operations listed are on the basis of servicing at intervals of six
m
onths or less.
Á W
ith closing and opening currents up to the continuous current rating of the circuit
breaker at voltages up to the rated maximum voltage (85% or higher power factor).
 The number of operations was determined with closing currents up to 600% and
opening currents up to 100% (80% power factor or higher) of the continuous current
r
ating of the circuit breaker at voltages up to the rated maximum voltage. With
closing and opening curre
nts up to 600% (50% power factor or less) of the continuous
current rating of the circuit breaker at voltages up to rated maximum voltage, the
n
umber of operations shown should be reduced to 10% of the number listed in the
column.
à If a fault operation occurs before the completion of the listed number of operations,
servicing is recommended and possible functional part replacement may be
necessary depending on previous accumulated duty, fault magnitude, and expected
future operations.
Design considerations
Standards and testing
WavePro
™
low voltage power circuit breakers are designed
and tested to meet ANSI Standards C37.13, C37.16, C37.17
and C37.50. The breakers are listed to UL 1066 and CSA
C22.2, and labeled to certify compliance with the above
referenced standards.
Power factors lower than test values affect the circuit breaker’s
short-circuit current rating. The test circuit X/R ratio and
power factor required by ANSI C37.13 is 6.6 and 15% for
unfused br
eakers and 4.9 and 20% for fused breakers.
Table 18.2 Derating factor for systems with power factors
low
er than test values
Temperature derating factors
The continuous current rating of WavePro breakers is based
on their use in an enclosure at 40° C ambient temperature
and 105° C maximum breaker temperature for Class A
i
nsulation. Continuous current ratings of WavePro breakers
must be derated for ambient temperatures above 40° C.
(
Trip unit ambient is limited to 70° C.)
Table 18.3 Continuous current derating factors
À Trip unit maximum
Altitude correction factors
When applying low voltage power circuit breakers at altitudes
greater than 6,600 feet, their continuous current rating must
be modified because a higher temperature use will be expe-
rienced for a given current rating. The voltage ratings must
also be modified because of the lower dielectric strength of the
air. The short-time and short-circuit current ratings are not
affected by altitude. However, the short-circuit current ratings
shall not exceed that of the voltage class before derating.
Table 18.4 Altitude correction factors (as listed in ANSI C37.13)
Humidity
Ferrous parts are zinc-plated for corrosion protection except
for some par
ts made fr
om alloy steels that are inherently
corrosion resistant. Current-carrying parts are silver- or tin-
plated for corrosion protection and to assure electrical conti-
nuity. Heaters may be added to indoor sections operating in
high humidity environments. Heaters are mounted in the
bus/ cable compartment in the rear of each section.
T
able 18.5
Insulation v
alues (Dielectric test)
Table 18.6 Operating time (Same for all frame sizes)
Close
Time from energizing closing
circuit until contacts touch
Electrically operated 5 Cycles
Open
Maximum clearing time
With instantaneous overcurrent trip 3 Cycles
W
ith shunt trip
3.5 Cycles
kV
Breaker 2.2
Control Wiring 1.5
Closing Motor 0.9
Altitude Rating correction factor
Meters Feet Continuous current Voltage
2000 6600 (and below) 1.00 1.00
2600 8500 0.99 0.95
3900 13000 0.96 0.80
Ambient temperature (°C) Derating factor
40 1.00
45 0.95
50 0.89
55
0.84 À
60 0.77
65 0.71
70 0.63
S
yst
em shor
t-
cir
cuit pow
er
factor (%)
System
X/R ratio
Derating factors for breaker
shor
t
-cir
cuit curr
ent rating
Unfused Fused
20 4.90 1.000 1.000
15 6.60 1.000 0.938
12 8.27 0.966 0.902
10 9.95 0.938 0.875
8.5 11.72 0.920 0.847
7 14.25 0.902 0.826
5 20.00 0.875 0.794
Circuit
b
reaker
frame size
(amperes)
Number of
o
perations
between
servicing
Number of operations
rated continuous
current switching
À
Á Ã
Number of
operations
on-load closing
a
nd opening À
Number of
operations
in-rush current
s
witching Â
Ã
800
1750 2800 9700 1400
1600
500 800 3200 400
2000
5
00
8
00
3
200
4
00
3200
2
50
4
00
1
100
—
4000
250 400 1100 —
5000
250 400 1100 —
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