Power Sensor Trip; Magnetic Coils - GE AK-2A-15 User Maintenance Manual

GENERAL DESCRIPTION
All AK-3 Type Air Circuit B reakers contain
Power Sensor Overcurrent Trip Devices.
P ower Sensor Trip functions with solid state
components with the exception of the Magnetic
Trip Device which is used to trip the breaker on
signal from the Power Sensor Unit.
Sensor Overcurrent Trip Device consists of four
major components.
1 . The m�gnetic coils around the breaker con­
ductors (Figure 14).
2.
The Power Supply which provides both the
tripping energy and the comparison basis for
overcurrent detection (Figure 1 5) .
3 . The Power Sensor Unit with the various pick­
up settings and time delay selection taps
(Figure 1 6 ).
4. The Magnetic Trip Device which physically
trips the breaker (Figure 17).
to
In addition the phase overcurrent protection,
a ground fault sensing feature may be provided.
POWER S E N S OR TR IP
The Ground Sensing Device works on the principle
that the instantaneous value of current flowing in
the three conductors (or; in four conductors on
The
four wire systems)
ground current is flowing.
electrical system is a four wire wye system with
the neutral grounded at the transformer, the fourth
The Power
sensing coil (Figure 1 8) must be included on the
neutral conductor with its secondary combined
with the secondaries of the three phase sensors
which are mounted on the breaker. On Draw-out
breakers, the output of the external neutral sensor
must enter the breaker by a control disconnect
(Figure 19) which is mounted low and on the center­
line on the back of the breaker. Refer to Figure
20 for Power Sensor Cabling diagram.
is indicated the trouble should be traced to one
or more of these four components involved, and
that component should be replaced as a unit. The
following steps should be taken to detect a mal­
functioning unit.
Figure 14. (804 1 866} Magnetic Coils
must add to zero unless
MAINTENANCE
When mal-functioning of the Power Sensor Trip
if
Therefore, the
2 5