Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 229)

COMMISSIONING 9-29
1557-UM050F-EN-P – June 2013
3. Start the drive. The step response of the current regulator is measured and the dc link time constant is
adjusted to produce a critically damped response. This test may take up to two minutes to perform.
When the desired response has been achieved the drive shuts off.
The current regulator bandwidth is set back to its normal value and parameter "Autotune select" is set to zero.
Parameter "Autotune Tdc" indicates the results of the test. If the test is successful, parameter "T dc link" in "P
Current Control" is set equal to "Autotune Tdc". If the test fails then parameter "T dc link" is not changed and a
warning is issued indicating the cause of the failure:
T dc low - indicates that the measured dc link time constant is less than 0.020 second. The step response of the
current regulator should be checked using the manual method described below.
T dc high - indicates that the measured dc link time constant is greater than 0.100 second. The step response of
the current regulator should be checked using the manual method described below.
Current Regulator Manual Tuning
An appropriate value for the “T dc link” parameter can be determined from the current regulator step response
while operating in dc current test mode. The following procedure should be followed:
1.
Be sure that all the parameters in the “P Nameplate” group have been set to the correct values, otherwise
the calculated value of parameter "L DC link” in “P Current Control” will not be correct.
2.
Set parameter "Test mode" in t he “P Feature Select” to 2 to enter dc current test mode.
Current Control Parameter Screen
3.
Set parameter "Idc command test” in “P Current Control” to 0.400 pu.
4.
Set parameter "Curreg Bandwidth" in “P Current Control” to 100 rad/sec. A lower than the normal
bandwidth makes the step response easier to measure.
5.
Set parameter "T dc link" in “P Current Control” to 0.020 sec, which is at the low end of the normal range
of values and should produce an underdamped response.
6.
Assign variables "Idc reference" and "Idc feedback" in “V Current Control” to two of the line converter
analog outputs (1 to 4) on the line converter (lower) control board and display them on a digital storage
oscilloscope. These may be assigned the same way the external meters are assigned.
7.
Start the drive. The dc link current will rise to 0.4 pu.
8.
Set parameter "Idc ref step" in “P Current Control” to 0.200 pu. The dc link current will step up and down
by this amount at regular intervals.