Rockwell Automation SD3000 Drive Configuration, Programming - Manual (Page 75)

The rate at which the CALC_RISE block parameter counts up and down is calculated so that a
step from 100% to LIM_BAR will turn on the OVERLOAD in TRIP-TIME seconds. If current
feedback steps from 100% to a value less than current limit, it will take longer to detect the
overload. If I_FDBK is stepped from zero to LIM-BAR, the block will take approximately four times
the value of TRIP-TIME to detect the overload.
UL 508C section 56.1.3 specifies that when subjected to 200% of rated full load motor current, the
overload protection must trip in at least eight (8) minutes. Because TRIP-TIME is calibrated from
100% to current limit, and TRIP-TIME from zero to current limit is approximately four times longer,
the maximum trip time that is allowed is 2 minutes (120 seconds). To meet UL listing
requirements, any value greater than 120 seconds is internally limited to 120 seconds.
The National Electric Code (430-32; 1993) requires that thermal overloads protecting motors
having a 1 .O service factor trip at load currents no greater than 115% of full load. To meet NEC
requirements, the THRESHOLD block parameter has a default value of 114% and should not be
set higher. Refer to instruction manual J-3676 for more information.
4.2.2 Local Tunable Variables
A set of local tunable variables with reserved (pre-defined) names is used to store different types of
values for use in drive control. For a description of the local tunable variables used in SD3000 drives,
refer to Appendix B.
All pre-defined local tunables must be defined in each UDC task (using the BASIC language LOCAL
statement) in order for the task to be loaded onto the UDC module. Although all of these variables
are not necessarily used in the UDC task itself, they must be defined there in order to provide a
mechanism for passing the values between the UDC module and the PMI. For convenience, all these
variables are already defined in the UDC task “skeleton” file in the AutoMax Programming Executive,
with “HIGH,” “LOW,” “STEP” and “CURRENT” values.
Your application task must define these variables using the same “HIGH,” “LOW,” and “STEP” limit
values as the ones found in the skeleton task. Note that you can only change the “CURRENT” value
in the application task. If the UDC operating system needs to clamp a value at the higher or lower
limit, it changes the actual value in the task and writes error code 958 into the error log for the task.
The local tunable values can be modified through the application task on the UDC module and by
the operator using the Monitor function. See the BASIC language instruction manual, J-3675, for
more information on local tunable variables and the WRITE-TUNE statement. Local tunable variables
cannot be forced.
Like all tunable values in the AutoMax environment, the values of these UDC task tunables are
retained through a power loss. Note that the programmer can also define other local tunable
variables for application-specific purposes, but that the total number of all local tunables in a UDC
task cannot exceed
127.
4.2.2.1 Calculating Local Tunable Values
Depending upon the type of local tunable variable, the “CURRENT” value, i.e.,
for the next s c a n of the PMI, can be determined in one of the following ways:
the value to be used
1. Self-tune.
The programmer can request the PMI to generate the values for some of the variables. For
example, the programmer can set the resolver calibration command bit in register 101 /1 101 to
cause the PMI to adjust the resolver balance.
When the PMI has generated the values, it sends them to the UDC module over the fiber-optic
link. The UDC module stores the values in the corresponding tunable variables. A copy of these
values is maintained in the PMI for use in the execution of the control algorithm.
2. Tune values from the Programming Executive software and tasks.
The Monitor function in the Programming Executive allows all local tunables to be modified
on-line within the limits defined in the LOCAL statement in the UDC task. Note that this is not
recommended for the resolver calibration values because these values can be generated more
precisely by the PMI during auto-tuning. At the end of the UDC task scan, the new values are sent
to the PMI to be used in the execution of the control algorithm.