Function Of The Spring Drive Mechanism; Charging The Closing Spring - Siemens 3AP2-FI Operation & Maintenance Manual

3 Description
3.7

Function of the Spring Drive Mechanism

The function of the spring drive mechanism is described below in conjunction with the major modular assemblies.
It is advisable first to read the section 3.6 Spring Drive Mechanism of the Circuit-Breaker.
3.7.1

Charging the Closing Spring

Starting position: the circuit-breaker is in the OPEN position. The closing and opening spring are relaxed, i.e. a
switching operation is not possible.
The cam disc 18.6 and the connecting rod 18.10 are near the lower dead centre point. The guide lever 18.7 and
operating lever 18.24 are rigidly connected and are in the OPEN position (Fig. 7).
To charge the closing spring, the charging shaft 18.14 is rotated by means of the charging motor 18.1 and gears
18.2. The free-wheel 18.3 engages in the cam of the charging shaft 18.14 (Fig. 8) and rotates it as far as the
upper dead centre point.
The charging shaft 18.14 is then turned as far as the closing latch 18.17 more quickly by the effect of the partly
relaxed closing spring 18.4 than by the freewheel, i.e. the form-fit between the free-wheel of the charging gear
and the charging shaft is cancelled and the charging shaft outpaces the charging gear. Before the cam plate 18.6
is stopped in the position 10° beyond the upper dead centre by means of the roller 18.23 and the closing latch
18.17 (Fig. 9), the cam 18.19 fixed to the mechanism housing disengages the free-wheel 18.3 from the charging
shaft 18.14 (Fig. 10). Charging shaft 18.14 and gear 18.2 are thereby separated. The motor is shut down
automatically and runs down with the gearing.
The closing spring is charged and the operating mechanism ready for the closing process.
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