GE AKR-30 Series Maintenance Manual page 45

SECTION Type SST Overcurrent Trip Device
10-
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 system.
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 circuitry for the various
trip elements. Their associated pickup and time delay ad­
justments (set-points) are located on the face plate. De­
pending on the application, programmer units may be
equipped with various combinations of Long Time, Short
Time, Instantaneous and Ground Fault trip elements. See
Table 7 for available ratings, settings and trip characteris­
tics. Adjustments are made by removing the clear cover
over the face plate, unscrewing (counter-clockwise) the
set-point knob, moving the set-point along the slot to the
new setting, and screwing the set-point knob in. Once all
adjustments are made, install the clear cover to the face
plate.
The SST programmer units can be optionally equipped
with trip indicators (targets). These are pop-out, me­
chanically-resettable plungers located across the top of
the programmer's front. Units 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 third for ground fault.
The latter is omitted on units without ground fault.
Bnaker
SIZe
Frame
Type
(Amperes)
AKR-30 800
AKR-50 1 600
AKRT-50 2000
CD
@
toler
11
Pitkup ante
toltnnte is
Pic:kup
TABLE SST TRIP CHARACTERISTICS
7
X
• Trip Ratinr
in Ampere.
• Sen.or Tap Lonr Time
- - -
( )
<D
- - - - - - - -
(
Pic:k (•L)
Sen.or
Am.,.re
Mult1p ..
Tapt
or X
- or -
100. 1 50. 225. 300
300 . 400. 600, 800
. . 7 .
.6 8.
300. 400. 600. 800 .9, 1 .0.
- or - 1 . 1 ( X )
600 . 800 . 1 200 . 1 600
800 , 1 200 .
1 600 , 2000
®
@
� �
�
1 0'\
•
FIG. 57 - SST BLOCK DIAGRAM
Each target pops out when its associated trip element
operates to trip the breaker. After a trip, the popped target
must be reset by hand. However, neglecting to reset does
not affect normal operation of any trip element or prevent
the breaker from being reclosed.
The programmer unit is mounted to the lower right 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.
SST
PROGRAMMER ADJUSTMENT RANGE
Short Time
®
@
) ( )
Time Pic:kup Time
Delay Delay
Band Multip .. Band
(Sec:onds) or L (Sec:onds)
3, 4, 5.
6, 8, 1 0 I L )
-o r -
Maximum Maximum
22 0.35
lntcrmed.
lntermed.
1 .7&, 2,
0.21
10
2.2&, 2.!i,
MUiimum Minimum
3, 4 ( L l
4 0.09&
60()'\
T ame delay shown a t or lonl time pickup s.ettinl (6L),
Time delay shown at lower limit of band.
( Set
Pointa)
GROUND FAULT
® ®
Instantaneous
@ ( ) (
)
Pickup
Pickup
Multiple Multiple
or L or X
.4, .5, .6,
. 8 . 1 .0 .
1 .2 ( X )
4, &, 6,
8, 10, 12 (L) .25, .3, .4,
(X)
.&, .6,
.7
.2, .25, .3,
.4, .&,
.6 (X)
It
lower limit of band.
OVOI.CWI
I TAIIGET
I
I
I
I
I
1 -
CIM:II I T
I TMW
I
@
Time
Delay
Band
(Sec:onda)
Maximum
0.30
lntermed .
0.1 6&
Minimum
0.065
45