Siemens Sinumerik 840D Series Function Manual page 46

2 Configuration
2.4 Connection
!
!
2-46
Warning
S
The DC supply must be safely electrically isolated.
See also:
References: /PHD/, Configuration NCU 561.2-573.2
S
The DC supply must be connected to the functional ground of the control at
one point (e.g. X131 on I/RF module). As a rule, the connection is provided
as standard in the S7-300 I/Os. See also:
References: /EMC/, SINUMERIK, SIROTEC, SIMODRIVE, EMC
Installation Guideline
S
The input for the 26.5 V supply is protected against polarity reversal.
26.5 V "2% must be fed from the external 26.5 V supply to connector X431
to supply the hydraulics components (servo solenoid valves, shut-off valves,
and pressure sensors). The power requirements is calculated from the
power required by external components plus 0.1 A for the internal circuit.
The input voltage tolerance relates to the input terminals of the closed-loop
control; the voltage drops on the supply leads are not negligible.
The external 26.5 V supply is monitored for violation of a lower limit in the
control.
Caution
After the external 26.5 V supply has powered up, terminal X431 may no longer
be inserted or switched since the high charging currents can irreparably
damage the module or external switch.
S
If the external 26.5 V supply has to be switched, then an external "precharg-
ing circuit" (e.g. relay with timer and resistor) must be used.
S
The 26.5 V outputs are short-circuit-proof or protected by fuses.
The outputs for the shutoff valves are designed as electronic switches with
integrated zener diodes for disconnecting inductive loads. The zener diodes
are located between the 24 V input and the output, with a typical zener volt-
age of 58 V.
On supply disconnection, the energy produced by the coil inductance and
the valve spool spring, plus the energy supplied from the 24 V source in the
zener diode and ohmic resistance in the solenoid coil is converted to heat.
This energy must not exceed 1.7 J during one power OFF process or else
the zener diode will be destroyed; no electronic protection against this type
of overload is available.
S
Other requirements of the external 26.5 V supply:
- Voltage range (mean value) 25.97 V to 27.03 V DC
- Ripple 240 mVpp
- No voltage dips, otherwise disconnection
SINUMERIK 840D/SIMODRIVE 611 digital, HLA Module (FBHLA) - 10.03 Edition
 Siemens AG, 2003. All rights reserved
02.99
10.03