Construction; Motor Operating Mechanism (Figure 6A); Mode Of Operation; Trip Free Operation (Figures 6A And 6B) - Siemens 3AH Series Instructions Manual

Vacuum Interrupter/Operator Description

Construction

The essential parts of the operating mecha nism are shown
in Figures 6a and 6b. The control and sequence of operation
of the mechanism is described in Figure

Motor Operating Mechanism (Figure 6a)

Th e spring ch arging motor (50.4) is bolted to the charg i n g
mechan ism (50.2) gear box instal led in t h e operator housing.
Neither the charging mech anism nor the motor require any
maintenance.

Mode of Operation

The operating mechanism is of the stored-energy trip free
type, i.e., the charging of the closing spri n g is not a utomati­
cally followed by the contacts cha n g i n g position, a n d the
closing function may be overridden by an opening com­
m and at any time.
When the stored-energy mechan ism has been charged, the
instant of operation can be chosen as d esired.
The mechanical energy for carrying out a n "open-close­
open" sequence for auto-reclosing d uty is stored in the clos­
ing and opening springs.
Charging
The details of th e closing spring cha rging mechanism are
shown in Figure 6a. The ch a rg i n g shaft is supported in the
charging mechanism (50.2), but is not coupled mech a n i­
cally with the charg i n g mech a n ism. Fitted to it are the cra n k
(62.2) a t one end, and t h e c a m (62.3), together with lever
(62.5), at the other.
When the charging mechan ism is actuated by hand with
a hand crank (Figures 9a and 9b) or by a motor (50.4), the
flange (50.3) turns until the driver (50.3.1 ) locates itself in
the cutaway part of the cam d isc (62.3), th us causing the
charg i n g shaft to follow. The cra n k (62.2) charges the closing
spring (62). When the closing spring has been fully cha rged,
the cra n k actuates the linkage ( 55.1 ) via the control lever
(55.2) for the "closing spring cha rg e d " ind icator (55), a n d
actuates t h e li mit switches (50.4.1 ) f o r interrupting t h e motor
supply. At the same time, the lever (62.5) at the other end
of th e charg i n g shaft is secu rely locked by the latching pawl
(62 .5.2). Wh en the closi ng spring is being charged, cam disc
(62.3) fol lows idly, i . e., it is brought i nto position for closing.
Closing (Figures 6a, 6b and 7 a - 7 d)
If the circ u it breaker is to be closed locally, th e closing spri ng
is released by pressing the CLOSE button (53) . I n th e case
of remote control, the close coil 52SRC (53.1 ) unlatches th e
closing spring (62).
As the closing spring d ischarges, th e ch arging shaft (62.1 ) is
turned by crank (62.2). The cam d isc (62.3) at the other e n d
o f t h e charging shaft actuates t h e d rive lever (62.6), with th e
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result that jack shaft (63) is turned by lever (63.5) via the trip
free cou pling rod (62.8). At the same time, the levers (63.1 ) ,
(63.5) a n d (63.7) fixed on t h e jack s h a ft operate the three in­
sulating couplers (48) (Figure 5) for the circuit breaker poles.
Lever (63.7) cha nges the Open-close ind icator (58) over to
Open. Lever (63.5) charges the opening spring (64) d u r-
i n g closing, a n d the circuit breaker is latched in the closed
position by lever (64.3) with pawl rol ler (64.3.1 ) and by pawl
(64.2). Lever (63.1 ) actuates the a uxiliary switch (68) th rou g h
t h e linkage (68.1 ) .
Th e crank (62.2) o n the charg i n g shaft (62.1 ) moves the link­
age (55.1 ) by acting on the control lever (55.2). The closing
spring charged ind ication is thus canceled, and the l imit
switches (50.4) switch in the control su pply to cause the
closing spri n g to recha rge immediately.

Trip Free Operation (Figures 6a and 6b)

The trip free coupling rod (62.8) permits th e immediate
decoupling of the d rive lever (62.6) a n d the jack s h aft (63) to
override closing action by trip command or by means of the
racking interlocks.
The trip free coupling rod (62.8) forms a link between the
drive lever (62.6) and the jack shaft (63). The rigidity of this
link depends upon a spring return latch (62.8.1 ) carried
within the coupling rod. The latch pivots within the cou pling
rod a n d is norm a l ly positioned to ensure the rigidity of the
coupling rod. Trip free coupling link (62.8.2) and trip free
coupling lever (62.8.3) cause the spring return latch posi­
tion to be dependent upon the normal tripping components
and the racki ng i nterlock. Thus, whenever a trip com mand is
a pplied or th e circuit breaker is not in the fully CONNECT or
TEST position, th e trip free coupling rod is no longer rigid,
effectively decou pling the d rive lever and jack shaft. U nder
these conditions the vacuum interrupter contacts cannot be
closed.
Opening (Figure 6a)
If the circuit breaker is to be opened locally, the openi n g
spring (64) is released by pressing the Open pushbutton
(54). In the case of an electrical command being given, the
trip coil 52T (54.1 ) unlatches the opening spring (64).
The opening spring (64) turns the jack shaft (63) via lever
(63.5); the sequence being similar to that for closing.
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