Siemens SINAMICS S120 Manual page 123

NOTICE
Damage to other loads as a result of overvoltage
Overvoltages of switched inductances (contactors, relays) can damage connected loads.
• Install suitable overvoltage protection circuits and devices.
Note
Malfunction because 24 V supply voltage is too low
If the 24 V supply voltage falls below the specified minimum value on a device in the
assembly, a malfunction can occur.
• Select an input voltage that is high enough for there to be sufficient voltage at the last
device. Do not exceed the maximum value for the supply voltage. If required, supply the
voltage to the assembly at various locations in the lineup.
Note
Operating motors with a built-in holding brake
A regulated DC power supply is required to operate motors with a built-in holding brake. The
voltage is supplied via the internal 24 V busbars. The voltage tolerances of the motor holding
brakes (24 V ±10%) and the voltage drops of the connecting cables must be observed.
Set the DC power supply to at least 26 V. This ensures that the supply voltage for the brake
remains within the permissible range when the following conditions are fulfilled:
• Siemens three-phase motors are used
• Siemens MOTION-CONNECT power cables are used
• Motor cable lengths, max. 100 m
Protective circuit against overvoltages
The Motor Modules have an integrated overvoltage protection circuit for the motor holding
brake. External protective circuits are not required.
Motor holding brake connection
To ensure reliable opening of the motor holding brake, it requires a typical voltage of 24 V ±
10% at the motor connection. Refer to the data sheet of the motor for the motor holding
brake voltage and tolerance.
● Also take into account that voltage drops occur in the motor module and on the supply
cable.
● Use a Control Supply Module or a regulated DC power supply whose setpoint is set to at
least 26 V.
● Note that there are motor holding brakes that close again when the maximum voltage is
exceeded.
Power Units in Booksize C/D-Type Format
Manual, 12/2018, 6SL3097-5AC20-0BP0
6.8 Possible functions of the 24 V supply
Cabinet design
121