Advertisement
Operating mechanism
The operating mechanism is comprised of the
mechanical and electrical components
required to:
1. Charge the closing springs with sufficient
potential energy to close the circuit
breaker and to store opening energy in
the tripping- and contact-pressure
springs.
2. Means to initiate closing and tripping
actions.
3. Means of transmitting force and motion
to each of three poles.
4. Operate all of these functions
automatically through electrical-charging
motor, cutout switches, anti-pump relay,
release (close and trip) solenoids and
auxiliary switches.
5. Provide indication of the circuit breaker
status (OPEN/CLOSED), spring condition
(CHARGED/DISCHARGED) and number of
operations.
Construction
The essential parts of the operating
mechanism are shown in Figure 15: Stored-
energy operating mechanism on page 19.
The control and sequence of operation of the
mechanism is described in Figure 17:
Operator sequence operation diagram on
page 23.
Indirect releases (tripping coils)
The shunt releases (54.1) convert the
electrical-tripping pulse into mechanical
energy to release the trip latch and open the
circuit breaker.
The undervoltage release (optional) (54.2)
may be electrically actuated by a make or a
break contact.
If a make contact is used, the coil is shorted
out, and a resistor must be used to limit the
current. The undervoltage-release option
mounts to the immediate right of the trip coil
(54.1).
Motor-operating mechanism
The spring-charging motor (50.4) is bolted to
the charging-mechanism (50.2) gear box
installed in the mechanism housing. Neither
the gear-box mechanism nor the motor
require any normal maintenance.
Auxiliary switch
The auxiliary switch (68.0) is actuated by the
jack shaft (63.0) and link (68.1).
Mode of operation
The operating mechanism is of the stored-
energy trip-free type. In other words, the
charging of the closing spring is not
automatically followed by the contacts
changing position, and the tripping function
prevails over the closing function in
accordance with ANSI/IEEE C37.04-1999,
clause 6.9 (for type GMSG) or ANSI/IEEE
C37.013, clause 6.3.8 (for type GMSG-GCB).
When the stored-energy mechanism has been
charged, the circuit breaker can be closed
manually or electrically at any desired time.
The mechanical energy for carrying out an
"Open-Close-Open" sequence for auto-
reclosing duty is stored in the closing and
tripping springs.
While the type GMSG-GCB generator circuit
breaker is capable of rapid reclosing duty, fast
reclosing should never be used in a generator
circuit to avoid major damage to the
generator.
Charging
The details of the closing-spring charging
mechanism are shown in Figure 15: Stored-
energy operating mechanism on page 19.
The charging shaft is supported in the
charging mechanism (50.2), but is not
coupled mechanically with the charging
mechanism.
Fitted to it are the crank (62.2) at one end,
and the cam (62.3), together with lever
(62.5) at the other.
When the charging mechanism is actuated by
hand with a hand crank or by a motor (50.4),
the flange (50.3) turns until the driver
(50.3.1) locates in the cutaway part of the
cam disc (62.3), thus causing the charging
shaft to follow. The crank (62.2) charges the
closing spring (62.0).
21
Advertisement
