Flying Restart - Siemens SINAMICS G150 Operating Manual

11/03
9.3.3

Flying Restart

Description
This function allows the cabinet unit to switch to a motor that is still rotating.
Switching the cabinet unit on without the flying restart function would cause an
overcurrent because the flow in the motor still has to build up and the open-
loop/closed-loop control must be set in accordance with the speed of the motor.
Two different situations are possible here:
a.) The drive rotates as a result of external influences, such as water (pump
drives) or air (fan drives). In this case, the drive can also rotate against the
direction of rotation.
b.) The drive rotates as a result of a previous shutdown, such as OFF 2 or a
power failure. The drive slowly coasts to a stop as a result of the kinetic energy
stored in the drive train (example: induced-draft fan with a high inertia load and
a steeply descending load characteristic in the lower speed range).
NOTE
The flying restart function must be used when the motor may still be running or is
being driven by the load to prevent shutdowns due to overcurrent.
SINAMICS G150
Operating Manual
Monitoring, Functions, and Protective Functions
9-7