Ambient Temperature; Operating Frequency - GE Power Break II Manual

Application
Table 44.1
Factor "A" - Cable Or Bus Size Multiplying Factor
Percentage of Rated
!Required) Cross-Sectional Area
(%)
50
60
7 0
8 0
9 0
1 0 0
1 2 5
zoo
150

Ambient Temperature

Ambient temperatures h ave a n even wider effect on the
rating of the b reaker-cable system. While the internal sens­
ing and tri p ping ci rcuitry with the Power+™, MicroVersa-
Trip Plus™ and M icroVersaTrip PM™ trip units a re a m bient
insensitive, hig h-am bient temperatures may cause i nternal
components to exceed their operating temperature l imits.
Low temperatures substantially i ncrease the current-carry­
ing capabilities of the breaker-ca ble system u nti l other lim it­
ing factors occur (e.g., lubrication problems or mechanical
binding of interna l parts due to d iffe rential contraction). The
-zooc
am bient tem perature of a Power Break®
be l ess tha n nor exceed + 70°C.
Cable with insulation rati ngs a bove
providing it is sized to 7 5°C, per the N EC, or other applicable
codes.
The term "am bient" temperature a lways refers to the tem­
perature of the air i m mediately surrounding the brea ker and
not the temperature of the a i r outside the breaker's enclo­
sure. Room or o utside air temperatures only esta blish the
thermal floor to which all other heati ng is a dded.
To convert breaker a m bient from room ambient, it is nec­
essary to know the temperature rise withi n the equipment
housing the breaker. The temperature rise is a function of
several varia bles, i ncluding heati ng caused by other equip­
ment , venti lation, solar heating, factors relating to g roup
mounting and the free surface a rea of the breaker's enclo­
sure.
Once the device's ambient temperature is determined, select
Factor B from the table.
44
Factor A
140
1 . 2 5
1 1 5
1 . 0 7
1 . 0 2
1.00
0.99
0.97
0.97
I I
b reaker should not
?soc
may be used,
Table 44.2
Factor "B" - Ambient Temperature Rating Factor
·c'
Ambient Tem perature Maximum Wire
I nsulating Rating
2 5
40
50
60
11
70
Notes: Average air temperature over a 24-hour period outside t h e break­
er's insulated case, but ir rside the enclosure. 2) Cable (wire) must be based
on 75oc a m pacities per Table 3 10-16. current National Electrical Code.
I I

Operating Frequency

All Power Break circuit breakers may be a p plied at their
published ratings on 50 Hz and 60 Hz power systems. At
nominal system frequencies less than 50 Hz but a bove d irect
current, digital solid-state trip devices become inoperative
due to sensor satu ration. On d i rect current systems, d ig ital
11
sol id-state trip u nits a re completely inoperative. Power Break
circuit breakers a re, therefore, not suita ble for direct cur­
rent applications.
System operating frequencies a bove 60 Hz may change the
performance and ratings of circuit breakers by heati ng me­
ta llic parts and sign ificantly reducing i nterrupting capacity.
Factor "C" Operating Freq uency
-
For operati ng freq uencies of both 50 Hz and 60 Hz, the
operating frequency rati ng foetor "C"
freq uencies other than 5 0 Hz and 60 Hz, derating factors
a re l isted below.
Table 44.3
Factor "C" - Frequency Rating
Frequency
•
de
50-60 Hz
150-180Hz
200-240 Hz
-·--·-
300-350 Hz
400-450 Hz
* Power+ t r i p units a n d t h e energy management functions in MicroVersaTrip
PM trip u n its are suitable far 50/60 Hz a pplications only
B
•c2
Factor
7 5 1.00
90 1.00
105 1.00
1 2 5 110
125 1 1 5
1.00. For operating
=
Factor C
-
1.00
1.07
1.25
140
1 . 5 1
C
" "