6.9
Drive availability
6.9.1
Flying restart – switching on while the motor is running
Overview
If you switch on the motor while it is still rotating, without the "Flying restart" function, there is
a high probability that a fault will occur as a result of overcurrent (F30001 or F07801). Examples
of applications involving an unintentionally rotating motor directly before switching on:
● The motor rotates after a brief line interruption.
● A flow of air turns the fan impeller.
● A load with a high moment of inertia drives the motor.
Requirement
The converter may operate precisely one motor only.
It is not permissible that you enable the "Flying restart" function if the converter is
simultaneously driving several motors. Exception: a mechanical coupling ensures that all of the
motors always operate with the same speed.
Function description
The "Flying restart" function comprises the following steps:
1. After the on command, the converter impresses the search current in the motor and
increases the output frequency.
2. When the output frequency reaches the actual motor speed, the converter waits for the
motor excitation build up time.
3. The converter accelerates the motor to the actual speed setpoint.
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Figure 6-87
Principle of operation of the "flying restart" function
Advanced commissioning
6.9 Drive availability
SINAMICS G120X converter
Operating Instructions, 06/2019, FW V1.01, A5E44751209B AC
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