SECTION 2-General Description
Type AKA low-voltage power c i rcuit breakers are used
for contro l l i ng and protecting power c i rcuits in the l ow
voltage range (usually up to 600 volts). I n serving this
function, they are a means of safely switching loads and
automatically clearing circuits when abnormal conditions
occur. Among these conditions, the more common are
short circuits and sustained overloads and under voltages.
The type AKA breakers are of the "quick-make, quick
break description, having the feature of storing energy in a
closing spring for quick release in closing. I n closing, some
energy is transferred to an opening spring to be used
subsequently for fast tripping.
Knowledge of how the breaker is designed and how it
operates will enable the owner to make proper use of the
breaker and to avoid mistakes in its operation . Specific
directions on adj ustments and maintenance procedu res
will be treated later.
The three main functional components of a breaker are
its mechanism, an assembly comprising the conductive
members, and the interrupter.
The mechanism unit is desig ned to receive energy, store
it, and later (when called upon to do so) deliver it to close
the breaker
:
contacts. It must be able to reverse its com
mitment to close the breaker at any point upon the activa
tion of an automatic trip device (i.e., be "Trip-Free"). Fi
nally, it also must be able to trip open a closed breaker
quickly enough to minimize arc erosion and in such a
manner as to effect proper arc transfer to the arc runner.
The current-carrying members of the breaker are as
sembled on the back frame, which provides the mechani
cal support required and also the insulating structure
needed. The conductive members are the studs for exter
nal connections, movable and stationary contact sets,
pivots for the movable contacts, and
provision for mounting
the current transformers.
The interrupter components are, in addition to the arcing
contacts, the arc runners mounted on the back base and
the removable arc quencher assemblies.
In addition to these basic components, a breaker may be
equipped with any combination 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 umber 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 amperes AC (AKAT
50/50H), 800 amperes D.C. (AKA 30) and 2000 amperes
D.C. (AKA 50) .
6
FIG. 1 - Manually Operated AKR-4A-50-1
These values represent the maxim u m continuous cur
rent capability of the respective frames. However, each
breaker carries a specific rating which is determi ned by the
current sensor ampere rating or maximum setting of the
trip device with which it is equipped.
2.2 OPERATION
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 required 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 in Fig. 3. They are not inter
changeable with Non-Fused breakers, since they require
deeper compartments for their fuses.
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