Capacitor Trip Device (Optional) - Siemens SDV-4A Instruction Manual

Interrupter/Operator Description
Figure 19. Circuit Breaker Limit Switches.
Inspection of the schematic diagrams shown in Figures 20a-
20b provides a clear picture of the logic states of the vari-
ous devices for the three basic control functions.
These are: 1) automatic charging of the closing springs;
2) electrical closing of the primary contacts and 3) electri-
cal tripping of the primary contacts.
Automatic spring charging by charging motor occurs when
secondary control power is available, and motor cutoff
switch LS1 has not operated. The springs are automati-
cally recharged after each closing operation.
Electrical closing occurs with closing control power applied
and when all of the following conditions exist:
1. External close switch 01/C is closed.
2. Anti-pump relay 52Y is not energized.
3. Auxiliary switch 52b indicates the breaker is in the open
position.
4. Limit switch LS3 shows that the trip latch has been reset.
5. Limit switch LS2 indicates that the closing springs are
charged.
Electrical tripping occurs with tripping control power ap-
plied and when the auxiliary switch 52a shows the breaker
is closed, and a trip signal is provided by the control switch
01/T or the protective relays. While external control power
is required for either electrical closing or tripping, the cir-
cuit breaker can be manually charged, closed and tripped
without external control power.

Capacitor Trip Device (Optional)

The capacitor trip device is an auxiliary tripping option pro-
viding a short term means of storing adequate electrical
energy to ensure breaker tripping.
2100-98
This device is applied in breaker installations lacking indepen-
dent auxiliary control power or station battery. In such instal-
lations, control power is usually derived from the primary AC
source. In the event of a primary source fault, or disturbance
with accompanying depression of the primary source voltage,
the capacitor trip device will provide short term tripping en-
ergy for breaker opening due to relay operation.
Refer to Figure 20b. An electrolytic capacitor resides across
the tripping supply voltage connected through a half wave
rectifier and resistor. The rectifier allows the capacitor to
assume a charge approximating the peak voltage of the
AC tripping supply voltage. The series resistor limits the
magnitude of charge current flowing into the capacitor.
The charged capacitor is then connected across the breaker
trip coil circuit through an external contact which closes
upon trip command.
The capacitor size and charge current magnitude are tuned
to the inductance and resistance of the tripping solenoid,
an RLC series circuit, to produce a discharge current through
the solenoid which emulates the magnitude of current and
current duration which the solenoid would experience if
operated from a DC tripping supply voltage.
Hazardous stored voltage.
Will cause death, serious injury or property
damage.
Make certain the energy stored in the
capacitor is discharged by grounding the
capacitor terminals before touching any of
the wiring.
2101-98
2102-98
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