Switching Operation; Operating Mechanism - Siemens 5-FSV-350 Installation Operation & Maintenance

Interrupter/Operator
Description
The contacts are designed so that a self-generated field causes
the arc to travel around the contacts. This prevents local ov­
erheating while interrupting large mag nitudes of short ci rcuit
cu rrent.
The ionized metal vapor arc discharge can only be maintained
if a certain minimum cu rrent flows. A cu rrent that does not
maintain this level may be extinguished abruptly p rior to cur­
rent zero. This chopping cu rrent m u st be kept to a minimum in
order to prevent unduly high overvoltages building up when
inductive circuits are switched . The use of a special contact
material ensures that cu rrent chopping i s limited to 4-5 Amp.
The rapid build-up of the dielectric strength in the break ena­
bles the arc to be safely extingu ished even if contact separa­
tion occurs immediately p rior to current zero.
The arc d rawn in the vac u u m b reaker i s not cooled. The metal
vapor plasma i s highly conductive and the resulting arc volt-
55.1
62
55
58
59
61 8
50
50.2 Charging mechanism
50 .4 Motor
Close button
53
53.1 Sring Release Coil 52SRC
54 Trip button
54.1 Shunt Trip Coil 52T
Closing spring charged
55
Indicator
55 .1 Linkage
Figure 9
Vacuum Breaker Mechanism Closed Position, Tripping
Springs Charged and Closing Springs Discharged
4 64.3 68
Open-close indicator
58
Operation counter
59
60 Mechanism housing
61.8 Dashpot
Closing spring
62
64
Opening spring
64
.3 Lever (Lever omitted when
applied to screw type racking)
68.7 Control Connector
age only attain s values between 20-200 V. For this reason and
because of the short arcing times , the arc energy developed
in the break is very smal l . This also accounts for the long elec­
y
trical l ife expectanc of the vac u u m I nterru pter
Owing to the hig h vacuum (less than 1 0 9 bar) in the interrupter,
contact clearances in the range of 6 to 20 mm (0.25 to 0.80
i nches) are adequate to attain a high dielectric strength.
Switching Operation ( Figure 6)
When a closing command i s initiated the closing spring, which
was previously charged by hand or by the motor, actuates the
moving contact, (36), through breaker shaft, (63), lever, (63.7 ) ,
insulated cou pler, (48), a n d lever, (48 . 6).
The forces that occu r when the action of the insulated coupler
is converted into the vertical action of the moving contact are
absorbed by g u ide link, (48 . 9 ) , which pivots on su pport, (40),
and eye bolt, (36.3)
During closing, the tripping spring and the contact p ressure
springs, (49), are charged and latched by pawl, (64 2)
The closing s p ring of motor-operated breaker is recharged im­
mediately after closing.
I n the closed state, the necessary contact pressure is main­
tained by the contact pressu re spring and the atmospheric
pressure. The contact pressure spring automatically compen­
sates for arc erosion, which is very smal l .
When a tripping command i s given, the energy stored in the
tripping and contact pressu re springs i s released by pawl ,
(64 . 2 ) . The opening sequence is similar to the closing se­
quence. The residual force of the tri pping s pring arrests the
moving contact, (36) i n the open position.

Operating Mechanism

The operating mechanism is comprised of the mechanical and
electrical components required to:
Charge the closing springs with sufficient potential en­
ergy to close the breaker and to store opening energy in
the tripping and contact pressure springs.
Mechanisms to release closing and tripping actions.
Means of transmitting force and motion to each of th ree
pole positions.
Operate all these functions automatically thru electrical
charging motor, c utout switches, antipumping relay, re­
lease solenoids , and auxil iary switches.
Signal thru ind icators the b reaker status , (open, closed)
and spring condition (charged or discharged) and num­
ber of operations.
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