Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 232)

9-32 COMMISSIONING
1557-UM050F-EN-P – June 2013
5. Leakage Inductance
Parameter “ L total leakage “ is used in the hardware reconstruction of the rotor flux. If this parameter is not
adjusted correctly, the resulting distortion in the flux feedback may cause speed feedback or motor
synchronization errors. Leakage inductance must be tuned during commissioning because it is effected not
only by motor parameters but also by cable length. Leakage inductance can be measured with the motor
stationary. The following Autotune procedure can be used
ATTENTION: In the following steps the rotation of the motor in an
undesirable direction may occur. To guard against possible equipment
damage, it is recommended that the motor be disconnected from the load
and tested for direction prior to proceeding, should the equipment be
sensitive to reverse direction rotation.
1.
Ensure that the motor is stationary. If the motor is turning the results of the test may be invalid. It is
not necessary to lock the rotor.
2.
Set parameter "Autotune select" in "P Autotune" to 5.
3.
Start the drive. The output frequency ramps up to rated frequency in 2-3 seconds with the motor current
remaining at zero. The motor current then jumps up to approximately rated current for less than a second
and the drive shuts off. This test produces a small amount of motor torque and some rotation may occur.
Parameter "Autotune Ls" is set to the measured leakage inductance and parameter "Autotune select" is set to
zero. If the test is successful, parameter "L total leakage" in "P Motor Model" is set equal to "Autotune Ls". If the
test fails then parameter "L total leakage" is not changed and a warning is issued indicating the cause of the
failure:
L leakage lo - indicates that the measured leakage inductance is less than 0.15 pu. Possible causes are:
1.
The motor is much larger than the drive and the motor nameplate parameters do not correspond to
the actual motor ratings. In this case, the measured leakage inductance is probably correct and
parameter "L total leakage" should manually be set equal to "Autotune Ls".
2.
Because of the design of the motor, this method of measuring leakage inductance does not produce
a valid result. The leakage inductance will have to be obtained from the motor data sheet, or if this is
not possible, parameter "L total leakage" should be set to its default value of 0.20 pu.
L leakage hi - indicates that the measured leakage inductance is greater than 0.30 pu. Possible causes are:
1.
The inductance of long motor cables is increasing the apparent leakage inductance of the motor. In this
case, the measured leakage inductance is probably correct and parameter "L total leakage" should
manually be set equal to "Autotune Ls".
2.
The motor is very small (leakage inductance generally increases with decreasing motor size).
3
Because of the design of the motor, this method of measuring leakage inductance does not produce a
valid result. The leakage inductance will have to be obtained from the motor data sheet, if this is not
possible, parameter “L total leakage should be set to its default value of 0.20 pu.