GE AKR-30 Series Maintenance Manual page 170

SECTION 2-General Description
Type AKA low-voltage power c i rcuit breakers are used
for contro l l i ng and protecti n g power c i rc u its i n the l ow­
voltage range (usual l y up to 600 volts). I n serving this
function, they are a means of safely switching loads and
automatical l y cl eari ng c i rcuits when abnormal conditions
occur. Among these conditions, the more common are
short circu its and sustained overloads and u nder voltages.
The type AKA breakers are of the "qu ick-make , qu ick­
break description, having the feature of storing energy in a
closi ng spring for quick release in closi ng. I n closing, some
energy is transferred to an opening spring to be used
subsequently for fast tripping.
Knowledge of how the breaker is desig ned and how it
operates will enable the owner to make p roper use of the
breaker and to avoid mistakes in its operation . Specific
d i rections on adj ustments and mai ntenance p rocedu res
will be treated later.
The three main fu nctional components of a breaker are
its mechanism, an asse mbly comprising the cond uctive
members, and the i nterrupter.
The mechanism unit is desig ned to receive energy, store
:
it, and later (when cal led upon to do so) deliver it to close
the breaker contacts. It m ust be able to reverse its co m­
m itment to close the breaker at any poi nt upon the activa­
tion of an automatic trip device ( i . e . , be "Trip- Free"). Fi­
nally, it also m ust be able to trip open a closed breaker
quickly enough to minim ize arc erosion and in such a
manner as to effect proper arc transfer to the arc runner.
The cu rrent-carrying members of the breaker are as­
sembled on the back frame, which provides the mechani­
cal su pport required and also the i nsulating structure
needed. The cond uctive members are the studs for exter­
nal con nections, movable and stationary contact sets,
pivots for the movable contacts, and provision for mounting
the current transformers.
The i nterrupter components are, in addition to the arcing
contacts, the arc runners mounted on the back base and
the removable arc quencher assemblies.
I n addition to these basic components , a breaker may be
equi pped with any co mbination of many accessories and
i nterlocking devices. Breakers may also differ in a variety
of areas as shown in Table 1 . A brief description of these
areas is given below.
M
outline d rawing is available for each breaker frame size
showing critical d imensions. The drawing n um ber appears on
the breaker nameplate and can be obtained from GE.
2 . 1 FRAME SIZE
The breakers are available in 5 frame sizes - 800 am­
peres A.C. (AKA 30/30H, AKAU 30) , 1 600 amperes A.C.
(AKA 50/50 H , AKAU 5 0 ) , 2000 am peres AC (AKAT
50/50H), 800 amperes D.C. (AKA 30) and 2000 amperes
D . C . (AKA 50) .
6
FIG. 1 - Ma nually Operated AKR-4A-50-1
These val ues represent the maxi m u m contin uous cur­
rent capability of the respective frames. However, each
breaker carries a specific rating wh ich is determi ned by the
current sensor ampere rating or maxi m u m setting of the
trip device with which it is equipped.
2.2 OPE RATION
There are Manual and Electrical breaker models. The
Manual breaker, shown in Fig. 1 , has an operati ng handle
which is used to manually charge the mechanism closing
spri ng.
The Electric breaker, shown in Fig. 2, contains an elec­
tric motor which charges the mechanism closing spring.
External control power is requi red to energize this motor
and its control circuit. A nameplate i ndicates what voltage
is required by the motor circuit and trip and close coils.
2.3 FUSED/NON FUSED
Fused breakers are identified as either AKAU 30 (800
ampere frame size) or AKAU 50 ( 1 600 ampere frame size).
A fused breaker is shown i n Fig. 3 . They are not i nter­
changeable with Non-Fused breakers, si nce they require
deeper compartments for their fuses.