Type Sst Overcurrent Trip Device; Programmer Unit - GE AKR-30 Series Maintenance Manual

SECTION 1 0-Type SST Overcurrent Trip Device
The SST is a solid-state, direct-acting, self-powered trip
device system . The SST system consists of the SST pro­
grammer unit, current sensors, and a flux shifter trip de­
vice . Fig. 57 shows a block diagram of the syste m .
1 0. 1

PROGRAMMER UNIT

Fig. 58 shows a typical SST programmer unit. The pro­
grammer unit provides the comparison basis for overcur­
rent detection and delivers the energy necessary to trip the
breaker. It contains the electronic circu itry for the vario us
trip ele ments. Their associated pickup and time delay ad­
justments (set-points) are located on the face plate. De­
pending on the application, programmer un its m ay be
equipped with various combinations of Long Time, Short
Time, I nstantaneous and G round Fault trip elements . See
Table 7 for available ratings, settings and trip characteris­
tics. Adj ustments are made by removi ng the clear cover
over the face plate, unscrewi ng (cou nter-clockwise) the
set-point knob, moving the set-point along the slot to the
new setting , and screwi ng the set-point knob in. Once all
adj ustments are made, install the clear cover to the face
plate.
The SST programmer un its can be optionally equipped
with trip ind icators (targets ) . These are pop-out, me­
chan ically-resettable plungers located across the top of
the programmer's front. U nits with a ground fault element
employ three targets: from left to right, the first is for over­
load, the second for short circuit (actuated by the short time
and instantaneous elements) and the th ird for ground fault.
The latter is om itted on units without ground fault.
Frame
Breaker
Size
Type
(Amperes)
AKR-30
800
AKR-50 1600
AKRT-50
2000
CD
@
Pickup tolerance is ±. 9%
Pickup tolerance is ±. 1 0%
TAB L E 7 SST TRIP CHARACTERISTICS
•
X Trip Rating
Long Time
• Sensor Tap
in Amperes
CD
(
- - - - - - ) - - -
- -
Pick (•L)
(
Sensor
Ampere
Multiple
Taps
of X
100, 1 50, 225, 300
- or -
300, 400, 600, 800
.6, .7, .8,
300, 400, 600, 800 .9, 1 .0,
- or - 1 . 1 (X)
600, 800, 1 200, 1600
800, 1 200,
1600, 2000
@
G)
8
t
)
- - - - - -
FIG. 57
Each target pops out when its associated trip ele ment
operates to trip the breaker. After a tri p, the popped target
must be reset by hand. However, neglecti ng to reset does
not affect normal operation of any trip element or prevent
the breaker from being reclosed.
The programmer unit is mou nted to the lower rig ht of the
breaker as shown in Fig. 59. The bracket attached to the
top of the programmer, see Fig . 58, engages with a bracket
mounted to the underside of the breaker's front frame.
SSf
PROGRAMMER ADJUSTMENT RANGE (Set Points)
Short Time
®
i e
( )
) @
T m Pickup Time
Delay Delay
Multiple Band
Band
(Seconds) of L (Seconds)
3, 4, 5,
6, 8, 10 (L)
Maximum Maximum
-or-
22 0.35
!ntdmed.
In termed .
1 . 75, 2,
0.21
10
2 . 2 5 , 2 . 5 ,
Minimum
Minimum
3, 4 (L)
4
0.095
Time delay shown a t 600% of long time pickup setting ( 6 L ) , a t lower limit of band.
Time delay shown at lower limit of band.
SST BLOCK DIAG RAM
-
GROUND FAULT
® ®
Pickup
Instantaneous
G) ( ) (
)
Pickup
L
Multiple Multiple
of of X
.4, .5, .6,
.8, 1 .0,
1.2 ( X )
4 , 5 , 6,
8, 10, 12 (L) .25, .3, .4,
.5, .6,
. 7 ( X )
. 2, .25, .3,
.4, . 5 ,
.6 ( X )
OYERlMD
1
TARGET
I
I
I
I
I
I SIID RT
lctRCUIT
TARGET
I
I
G)
Time
Delay
Band
(Seconds)
Maximum
I
0 . 30
In termed.
0 . 1 6 5
Minimum
0.065
45