Siemens siprotec 7SA522 User Manual page 465

7SA522 Manual
C53000-G1176-C119-2
So the circuit breaker trip coil does not remain energized in the above case, R
derived as:
U

CTR
⋅
R = R ---------------------------------------------- -

min TC
U
TC (LOW)
I Constant current with BI on
BI (HIGH)
Minimum control voltage for BI
U
BI min
=17 V for delivery setting for nominal voltage of 24/48/60 V;
=73 V for delivery setting for nominal voltage of 110/125/220/250 V;
= 154V for delivery setting for nominal voltage of 220/250 V
Control voltage for trip circuit
UCTR
R DC resistance of circuit breaker trip coil
CBTC
U Maximum voltage on the circuit breaker trip coil that does not lead to tripping
CBTC (LOW)
If the calculation results that R
the next lowest switching threshold U
in the relay using plug-in bridges (see Sub-section 8.1.3).
For the power consumption of the resistance:
U

2
CTR
⋅
P I R --------------------------- -
= =

R
R + R
Example:
I
1.7 mA (from SIPROTEC
BI (HIGH)
U 17 V for delivery setting for nominal voltage 24/48/60 V
BI min
73 V or delivery setting for nominal voltage 110/125/220/250 V
154V for delivery setting for nominal voltage of 220/250 V
UCTR 110 V (from system / release circuit)
500 Ω (from system / release circuit)
R
CBTC
U 2 V (from system / release circuit)
CBTC (LOW)
R = 54.8 kΩ
max
R 27 kΩ
=
min
R + R
max min
------------------------------- -
R = =
2
R
max
The closest standard value of 39 kΩ is selected; the power is:

110 V
P = --------------------------------------- -

R
39 kΩ 0.5 kΩ
+
≥
P 0.3 W
R
U
–

TC (LOW)

< R , then the calculation must be repeated, with
max min
, and this threshold must be implemented
BI min
2

⋅
R

CBTC
®
7SA522)
40.9 kΩ
 
110 V 16 V
–
500 Ω
--------------------------------- -
= –
 
1.7 mA
2

⋅
39 kΩ

Installation and Commissioning
is
min
8-9