Operating Instructions ACU
No auto start. The drive is accelerated, after application of the mains
voltage, as soon as the release and the start command are present
(edge based).
The drive is accelerated by the frequency inverter as soon as the mains
voltage is applied (level based).
13.5 Search run
The synchronization to a rotating drive is necessary in applications which drive the motor by their
behavior or in which the drive is still rotating after an error switch-off. Via Operation Mode Search
Run 645, the motor speed is synchronized to the current motor speed without an "Overcurrent"
error signal. After this, the motor is accelerated to the reference speed at the set acceleration. This
synchronization function determines the current rotary frequency of the drive via a search run in
operation modes 1 to 5.
The synchronization in operation modes 10 to 15 is accelerated by short test impulses. Torsional
frequencies up to 175 Hz are determined within 100 ms to 300 ms. For higher frequencies, a wrong
frequency is determined and the synchronization fails. In the "Quick synchronization" operation
modes, the search run cannot determine whether an synchronization attempt has failed.
For operation of a synchronous motor, the flux direction can be determined in order to prevent
alignment of the motor shaft (jerking) during start-up. Determining the flux direction takes approx.
20 ms. In this process, there are short torque pulses. This method is not suitable for very dynamic
drives since the torque pulses result in a rotation of the drive and consequently in wrong
measurements. Once the flux direction has been determines, the flux is built up (parameters Min.
Flux-Formation Time 779, Max. Flux-Formation Time 780, Current during Flux-Formation 781)
in order to improve the starting behavior.
The synchronization to a rotating drive is deactivated.
Search Dir.
acc. to Preset Val.,
DCB
The search direction is defined by the sign of the setpoint. If a positive
setpoint (clockwise field of rotation) is entered, the search is in a
positive direction (clockwise field of rotation), with a negative setpoint,
the search is in a negative direction (anticlockwise field of rotation).
First clockw. then
anticlockw., DCB
The first attempt is to synchronize to the drive in positive direction
(clockwise field of rotation). If this attempt fails, it is tried to synchronize
to the drive in negative direction (anticlockwise field of rotation).
First anticlockw. then
clockw., DCB
The first attempt is to synchronize to the drive in negative direction
(anticlockwise field of rotation). If this attempt fails, it is tried to
synchronize to the drive in positive direction (clockwise field of rotation).
Synchronization to the drive is only done in positive direction (clockwise
field of rotation).
Synchronization to the drive is only done in negative direction
(anticlockwise field of rotation).
An attempt is made to synchronize to the drive in positive direction
(clockwise field of rotation) and in negative direction (anticlockwise field
of rotation).
Quick Synch. acc. to
Preset Value
The search direction is defined by the sign of the setpoint. If a positive
setpoint (clockwise field of rotation) is entered, the search is in a
positive direction (clockwise field of rotation), with a negative setpoint,
the search is in a negative direction (anticlockwise field of rotation).
Quick Sync.,
Clockwise Only
Synchronization to the drive is only done in positive direction (clockwise
field of rotation).
Quick Sync., Anti-
clockwise Only
Synchronization to the drive is only done in negative direction
(anticlockwise field of rotation).
Operation modes 1, 4 and 5 define a direction of rotation for the search run and avoid a deviating
direction. The search run can accelerate drives by checking the rotary frequency if the drives have a
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