12.5 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 a fault switch-
Via Operation mode search run 645, the motor speed is synchronized to t
motor speed without an "Overcurrent" fault message. After this, the motor is acceler-
ated to the reference speed at the set acceleration. This synchronization function
determines the current rotary frequency of the drive via a search run in opera
modes 1 to 5.
The synchronization in operation modes 10 to 15 is accelerated by short test im-
pulses. Rotary frequencies of up to 175
Hz are determined within 100 ms to 300 ms.
For higher frequencies, a wrong frequency is determined and the synchroniz
fails. In the "Quick synchronization" operation modes, the search run cannot deter-
mine whether a 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 direc-
tion was determined, the flux is formed (Parameter
Minimum flux-
779, Maximum flux-formation time 780, Current during flux-formation 781
) in
order to improve the starting behavior.
0 - Off The synchronization to a rotating drive is deactivated.
1 -
Search Dir. acc. to
Preset Val.,
DCB
The search direction is defined by the sign in front of the
reference value. If a positive reference value (clockwise
field of rotation) is entered, the search is in a positive di-
rection (clockwise field of rotation), with a negative refer-
ence value, the search is in a negative direction (anti-
clockwise field of rotation).
2 -
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).
3 -
First anticlockw.
then clockw.,
DCB
The first attempt is to synchronize to the drive in nega-
tive direction (anticlockwise field of rotation). If this at-
tempt fails, it is tried to synchronize to the drive in posi-
tive direction (clockwise field of rotation).
4 -
Synchronization to the drive is only done in positive di-
rection (clockwise field of rotation).
5 -
Synchronization to the drive is only done in negative
direction (anticlockwise field of rotation).
10 -
Quick Synchroniza-
tion
An attempt is made to synchronize to the drive in positive
direction (clockwise field of rotation) and in negative
direction (anticlockwise field of rotation).
11 -
Quick Synch. acc. to
Preset Value
The search direction is defined by the sign in front of the
reference value. If a positive reference value (clockwise
field of rotation) is entered, the search is in a positive di-
rection (clockwise field of rotation), with a negative refer-
ence value, the search is in a negative direction (anti-
clockwise field of rotation).
14 -
Quick synch.,
clockw. only
Synchronization to the drive is only done in positive di-
rection (clockwise field of rotation).
15 -
Quick synch.,
anticlockw. 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 low moment of inertia and/or a small load mo-
142 Operating Instructions ACU 06/13
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