Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 233)

COMMISSIONING 9-33
1557-UM050F-EN-P – June 2013
6. Flux Regulator
For the flux regulator, different tuning procedures are used for induction motors and synchronous motors.
Induction Motor Flux Regulator
The tuning of the flux regulator for an induction motor is determined by three parameters:
1. Flxreg bandwidth in "P Flux Control"
2. L magnetizing in "P Motor Model"
3. T rotor in "P Motor Model"
"Flxreg bandwidth" should be set to the default value for almost all applications. "L magnetizing" and "T rotor" are
usually unknown and must be measured. Both of these motor parameters change substantially with different
operating conditions, but the variations do not significantly affect the operation of the flux regulator.
The other aspect of flux control is the variation of motor flux with speed. This is determined by two parameters in
the "P Flux Control" group:
1. Base speed
2. Flux command base speed
Note: A third parameter, “Flux command zero speed”, present in firmware revisions prior to 4.55 has been deleted.
In most applications, the motor runs at constant flux below rated speed and constant voltage above rated speed.
The motor flux is normally set to a level that provides rated voltage at rated speed and full load. The flux level
required to achieve this is a function of the motor parameters. The flux regulator Autotuning determines a value of
rotor flux that should provide rated motor voltage at full load and rated speed and sets the flux command
parameter to this value.
Flux Regulator Autotuning
The flux regulator is tuned with the motor running at constant speed using the following procedure:
1.
Ensure that parameters "Rated motor rpm" in "P Nameplate" and "L total leakage" in "P Motor Model" are
set to the correct value.
2.
Set parameter "Autotune select" in "P Autotune" to 6.
3.
Start the drive. The motor accelerates normally up to the speed specified by parameter "Autotune spd
cmd". The motor magnetizing inductance is calculated from the measured current and flux feedback and
parameter "Autotune Lm" is set to this value. The flux command is then set to a value that should
produce rated voltage at rated speed and load. The resulting change in the flux level
may cause the
magnetizing inductance to change. This process is repeated until the magnetizing inductance and flux
command stabilize. The drive then performs a normal stop.
Parameter "Autotune Lm" is set to the measured magnetizing inductance and parameter "Autotune select" is set to
zero. Parameter "Flux Command Base Speed" in "P Flux Control" is set to a value which is intended to produce
rated voltage at rated speed and load. The value of parameter "Autotune T rotor" is calculated from parameters "L
magnetizing" and "Rated Motor rpm" (which gives the rated slip).
If the flux regulator Autotuning is successful, then parameter "L magnetizing" in "P Motor Model" is set equal to
"Autotune Lm", parameter "T rotor" in "P Motor Model" is set equal to "Autotune T rotor", and the flux regulator
gains are recalculated. If the flux regulator Autotuning fails then parameters "L magnetizing" and "T rotor" are not
changed and a warning is issued indicating the cause of the failure.