Siemens H-compact PLUS, Operating Instructions Manual

Page: 12 / 83

Safety information
2.3 Switching high-voltage motors
WOGeneric TEAAC / 2008
10
Siemens AG Operating Instructions 1.03 1RQ671...-Z
Those responsible for plant safety must ensure the following:
● The basic planning work for the system and all work relating to transportation, assembly,
installation, commissioning, maintenance and repairs is carried out by qualified personnel
and checked by responsible, suitably skilled personnel.
● The operating instructions and machine documentation are always available.
● The technical data and specifications relating to installation, connection, ambient and
operating conditions are taken into account at all times.
● The system-specific installation and safety regulations are observed.
● Personal protective equipment is used.
● Work on or in the vicinity of these machines by unqualified persons is prohibited.
● If the machines are used outside industrial areas, the installation site must be
safeguarded against unauthorized access by means of suitable protection facilities (e.g.,
safety gates) and appropriate warning signs.
Note
Siemens Service Center
We recommend engaging the support and services of your local Siemens Service Center
(Page 69) for all planning, installation, commissioning, and maintenance work.
[ID 2.02]
2.3 Switching high-voltage motors
Switching overvoltages
If vacuum circuit breakers and vacuum contactors are used, what are known as multiple
restrikes can occur when the machine is switched off. This depends on various factors, such
as:
● arc-extinguishing principle of the switch,
● size of the motor,
● length of the power supply cable,
● system capacitance, etc.
CAUTION
Switching overvoltages
In some cases, multiple restrikes can result in switching overvoltages which are too high
for the insulation of the motor stator winding. This occurs when high-voltage motors with
starting currents I
A
≤ 600 A are disconnected during startup or following a blockage.
The peak voltages which arise as a result can damage the winding insulation.
If you are using vacuum circuit breakers and vacuum contactors, use an appropriate
surge suppressor, such as the Siemens 3EF (zinc oxide varistor with spark gap).