Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 235)

COMMISSIONING 9-35
1557-UM050F-EN-P – June 2013
Synchronous Motor Flux Regulator
This section applies only to firmware revision 5.10 and higher.
Before the flux regulator can be tuned, the analog output for the field current reference must be set up.
Configuring the Field Current Reference
Excitation for the synchronous motor is provided by a current regulated field supply, either a dc supply for a slip
ring machine, or a three phase ac supply for a brushless machine. The drive provides an analog current reference
as an input to the field supply. The analog current reference has a range of 0-10V, where 0V corresponds to zero
field current and 10V corresponds to maximum field current. The scale and offset of the analog current reference
must be adjusted to achieve a linear relationship between the current reference and the actual field current. If this
is not done, the flux regulator may be unstable. The scale and offset of the analog output can be adjusted using
the following procedure:
1.
Assign variable “I field command” in “V Flux Control” to the analog output used to control the field supply
(normally analog output 4L)
2.
Set th e analog output scale parameter (e.g. Analog Scale 4L) in “P Analog Output” to:
Analog Scale = maximum analog input of field supply / 10V
3.
Set the analog output offset parameter (e.g. Analog Offset 4L) in “P Analog Output” to it maximum value of
9.92V.
Confirm that the analog output variable (e.g. Analog Output 4L) in “V Analog I/O” is at its maximum
value of 9.92V. Confirm that the reference input of the field supply is also at its maximum value.
4.
Start the field supply and confirm that the field current goes to its maximum value. If necessary, adjust the
field supply to achieve a field current slightly above rated. When the desired field current has been
achieved, set the analog output offset back to 0.00V.
CAUTION: Applying maximum field current to a stationary machine for an extended period may damage the
exciter. Adjust the current as quickly as possible.
5.
Adjust the analog output offset to a level at which the field supply just begins to supply current. This
compensates for any offset in the field supply current reference input.
6.
Repeat steps 3 to 5 until the correct scale and offset adjustments are obtained.
7.
Stop the field supply. The setup of the field current reference is complete and you can proceed with the
tuning of the flux regulator.