4.9 Torsional loading of the drive train due to faults in the electrical supply
In the event of faults in the electrical connection, such as line switching operations with a
residual field or short circuit at the terminals, excessive air gap torques can occur. These
excessive air gap torques can lead to additional mechanical torsional loads on the shaft
assembly.
If the configuration does not correctly recognize the mechanical torsional loadings of the shaft
assembly, this can lead to serious damage to the machine. This can result in death, serious
injury or material damage.
● When planning the system, make due allowance for the maximum air gap torques that can
occur. This data can be found in the "Electrical data".
The system planner is responsible for the entire drive train.
4.10 Switching high-voltage motors
If vacuum circuit breakers and vacuum contactors are used, then 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
● Machine size
● Length of the power supply cable
● System capacitance, etc.
A surge suppressor to ground is installed in the switchgear between the circuit breaker and
the cable termination for each of the three conductors. The level of protection for the machine
windings is sufficient when the limiter is correctly selected (machine rated voltage / response
voltage).
Example
This current limit corresponds to the following upper power limits, depending on the relationship
between the starting current I
A
and rated current I
N
and on the voltage dip (up to approximately
20%) while the machine is starting up:
Table 4-1 Power limits
Rated voltage V
N
Power limit
3 kV 750 kW
6 kV 1500 kW
10 kV 2500 kW
See also
Prior to commissioning (Page 69)
Preparations for use
4.9 Torsional loading of the drive train due to faults in the electrical supply
SIMOTICS HV C 1NB1402-2AA84-4CA0-Z
Operating Instructions 06/2018 25
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