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Design Considerations - GE AKD-10 Application Manual

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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)
Circuit
Number of
Number of operations
breaker
operations
rated continuous
frame size
between
current switching
Œ  
(amperes)
servicing
800
1750
2800
1600
500
800
2000
500
800
3200
250
400
4000
250
400
5000
250
400
ΠServicing consists of adjusting, cleaning, lubricating, tightening, etc., as recommended
by the manufacturer. When current is interrupted, dressing of contacts may be
required as well. The operations listed are on the basis of servicing at intervals of six
months or less.
 With 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).
Ž 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
rating of the circuit breaker at voltages up to the rated maximum voltage. With
closing and opening currents 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
number of operations shown should be reduced to 10% of the number listed in the
column.
 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 breakers and 4.9 and 20% for fused breakers.
Table 18.2 Derating factor for systems with power factors
lower than test values
Derating factors for breaker
System short-
System
short-circuit current rating
circuit power
X/R ratio
factor (%)
Unfused
20
4.90
1.000
15
6.60
1.000
12
8.27
0.966
10
9.95
0.938
8.5
11.72
0.920
7
14.25
0.902
5
20.00
0.875
18
Number of
Number of
operations
operations
on-load closing
in-rush current
and opening Œ
switching Ž 
9700
1400
3200
400
3200
400
1100
1100
1100
Fused
1.000
0.938
0.902
0.875
0.847
0.826
0.794
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
insulation. 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
Ambient temperature (°C)
Derating factor
40
1.00
45
0.95
50
0.89
0.84 Œ
55
60
0.77
65
0.71
70
0.63
ΠTrip 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)
Altitude
Meters
Feet
Continuous current
2000
6600 (and below)
1.00
2600
8500
0.99
3900
13000
0.96
Humidity
Ferrous parts are zinc-plated for corrosion protection except
for some parts made from 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.
Table 18.5 Insulation values (Dielectric test)
kV
Breaker
2.2
Control Wiring
1.5
Closing Motor
0.9
Table 18.6 Operating time (Same for all frame sizes)
Close
Time from energizing closing
Electrically operated
circuit until contacts touch
With instantaneous overcurrent trip 3 Cycles
Open
Maximum clearing time
With shunt trip
Rating correction factor
Voltage
1.00
0.95
0.80
5 Cycles
3.5 Cycles

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