Siemens 38-3AH3 38 kV Operating mechanism, Indirect releases tripping coils, Auxiliary switch

When a tripping command is given, the energy stored in the tripping- and contact- pressure springs is released by pawl (64.2). The opening sequence is similar to the closing sequence. The residual force of the tripping spring arrests the moving contact (36.0) in the OPEN (TRIPPED) position.

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 20. The control and sequence of operation of the mechanism is described in the Operating mechanism section diagrams in Figure 17-21 on pages 24 through 28.

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.

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.

Charging

The details of the closing-spring charging mechanism are shown in Figure 15: Stored-energy operating mechanism on page 20. 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).