Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C Frame) - Classic Control - Manual (Page 339)

Functional Description 5-31
7000 “C” Frame 7000L-UM300I-EN-P – June 2013
For all multiple motor synchronizing applications, a PLC is used for
overall control of the synchronous transfer operation. Typically, the
PLC gives control of the bypass contactor to the drive before
performing the transfer, and takes back control after the transfer is
completed.
Note: The following note applies only to applications using PLCs.
A T T E N T I O N A T T E N T I O N Since the programmable controller and not the
drive controls the output and bypass contactors,
the transfer command must always go via the
PLC and never directly to the drive from another
controlling device (e.g. a Remote I/O adapter).
The following section will describe the sequence of operation on
single motor synchronous transfer without using a PLC.
Transfer to Bypass
When the motor is running on the drive and a synchronous transfer is
required, the transfer takes place in the following sequence:
1. The drive is given a Request to Bypass command, which must
remain active until the synchronous transfer is complete. If the
transfer command is removed before the bypass contactor is
requested to close, the drive will abort the transfer and return to
normal running. When the drive receives the transfer command,
it accelerates the motor up to the measured Bypass Freq (159).
If the drive is unable to achieve synchronous speed, it may be
necessary to increase parameter Trq Lmt Motoring (84).
2. When the motor reaches synchronous speed, the synchronizing
regulator is activated whose response is controlled by parameter
Sync Reg Gain (225). It adjusts the drive Speed Reference as
required, to synchronize the motor to the bypass with the motor
voltage leading the bypass voltage by an angle specified by
parameter Sync Lead Angle (226). This parameter is used to
compensate for the drifts in the motor and bypass voltage before
the bypass contactor closes. If the phase error tends to oscillate,
it may be necessary to adjust parameters Sync Reg Gain or
Spdreg Bandwidth.