Siemens 38-3AH3 38 kV Capacitor-trip device, Shock absorber, Secondary disconnect

Figure 27: Secondary disconnect on the circuit breaker

Figure 28: Secondary disconnect inside the switchgear

Figure 29: Auxiliary switch

When this happens, the latch (25.0) loses its support and releases the striker pin (23.0), that is forced out by the spring (31.0).

On the undervoltage release 3AX1103, the latch (25.0) is held by the locking pin (21.0) as long as the armature (9.0) is attracted (energized) (refer to Figure 21: Operator sequential operation diagram on page 28). If the circuit of the magnet coil (7.0) is interrupted, the armature (9.0) drops off, thus causing the latch (25) to lose its support and release the striker pin (23).

Following every tripping operation, the striker pin (23.0) must be reset to its normal position by loading the spring (31). This takes place automatically via the operating mechanism of the circuit breaker.

Since the striker pin of the undervoltage release 3AX1103 is latched only when the armature is attracted, this trip is provided with a screw (29.0) (refer to Figure 25: Undervoltage lock/operate selection on page 31).

This screw is provided to allow locking the striker pin (23.0) in the normal position for adjusting purposes or for carrying out trial operations during circuit breaker servicing. Position A (locked) disables the undervoltage release. Position B is the normal (operating) position.

Capacitor-trip device

The capacitor-trip device is an auxiliary tripping option providing a short-term means of storing adequate electrical energy to ensure circuit breaker tripping.

This device is applied in circuit breaker installations lacking independent auxiliary- control power or a station battery. In such installations, control power is usually derived from the primary source. In the event of a primary-source fault, or disturbance with resulting reduction of the primary-source voltage, the capacitor-trip device will provide short-term tripping energy for circuit breaker opening due to the protective relay operation.

The capacitor trip includes a rectifier to convert the 120 or 240 Vac control voltage to a dc voltage that is used to charge a large capacitor to the peak of the converted-voltage wave (refer to Figure 26: Capacitor trip device on page 31).

Shock absorber

A type 38-3AH3 vacuum circuit breaker is equipped with a sealed, oil-filled, viscous damper or shock absorber (61.8) (refer to Figure 15: Stored-energy operating mechanism on page 20). The purpose of this shock absorber is to limit overtravel and rebound of the vacuum interrupter movable-contacts during the conclusion of an opening operation. The shock-absorber action affects only the end of an opening operation.

Secondary disconnect

Signal and control power is delivered to the internal circuits of the circuit breaker by an arrangement of movable-contact fingers (refer to Figure 27: Secondary disconnect on the circuit breaker) mounted on the top of the circuit breaker.

When the circuit breaker is racked into the TEST or CONNECT position in the metal- clad switchgear, these disconnect fingers engage a mating-disconnect block on the inside of the switchgear (refer to Figure

28:Secondary disconnect inside the switchgear). These electrical connections automatically disengage when the circuit breaker is racked from the TEST to the DISCONNECT position.

All of the control power necessary to operate the circuit breaker is connected to this disconnect block inside the switchgear. The external trip- and close- circuits and associated circuits are also connected to the same disconnect block.

Auxiliary switch

Figure 29: Auxiliary switch shows the circuit breaker mounted auxiliary switch. This switch provides auxiliary contacts for control of circuit breaker closing and tripping functions. Contacts are available for use in relaying and external logic circuits. This switch is driven by linkages connected to the jack shaft.