Surge Voltage Protection; Line Contactors - Siemens SINAMICS S120 Manual

Mains connection and line-side power components

3.5 Surge voltage protection

Conditions when using differential current monitoring devices
● Use only AC/DC-sensitive RCM type B devices with delayed tripping that guarantee
reliable tripping even for smoothed DC residual currents.
● Connect parts of the power drive system and the machine that can be touched to the PE
conductor of the plant.
● Do not route the PE conductor through the measuring current transformer because this
would remove its protection function.
3.5 Surge voltage protection
To protect the units against line-side surge voltages, install an overvoltage protection device
(surge arrester) directly at the infeed point. For use in Canada, to comply with the
requirements of CSA C22.2 No. 274, a UL category VZCA and VZCA7 surge arrester is
absolutely mandatory. The Raycap company has suitable surge arresters.
3.6

Line contactors

A line contactor is required if the drive line-up needs to be electrically isolated from the
power supply.
When selecting a line contactor, the characteristic values in the technical data apply. The
cables and conductors to be connected must be dimensioned in compliance with local
installation regulations.
NOTICE
Damage to the drive electronics when switching the line contactor under load
If you switch the line contactor (recommended type) under load, the contacts will wear out
prematurely. This may lead to faulty functioning of the contactor with subsequent damage
to the drive electronics.
• Use a leading, opening auxiliary contact.
• If this is not possible, avoid switching the line contactor under load.
Note
To limit the switching overvoltage, the contactor coil must be connected to a surge
suppression device (e.g. freewheeling diode or varistor).
When a digital output is used to control the line contactor, its switching capacity must be
taken into account.
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Manual, (GH6), 07/2016, 6SL3097-4AL00-0BP5
AC Drive