Rockwell Automation SA500 AC Power Modules - Manual (Page 40)

4-12 SA500 Power Modules
Balance Calibration
The balance calibration procedure is initiated by setting UDC register 101/1101, bit 6
(RES_CAL@) after turning the drive on. The procedure takes from a few seconds to
one minute to complete. It must be performed while the resolver is rotating at 5 RPM
minimum speed (speed does not have to be constant). The faster the resolver is
turning, the faster the balance calibration procedure will be performed. Balance
calibration compensates for different cable lengths or characteristics. For example,
one twisted-pair wire can yield more or less capacitance than another twisted-pair
wire of the same length. Therefore, one channel could have more or less voltage on it
than the other. If each stator winding has different capacitance on it, different
response curves result. These curves should be equal for optimum performance.
The balance calibration procedure minimizes oscillations that occur due to imbalances
between channels by adding capacitance to the sine or cosine channel. The operating
system calculates the capacitance value which yields the smallest velocity variations
with sine/cosine magnitudes within 1% of each other. Due to the characteristics of the
cable or to noise problems, it is possible that the magnitudes will not be within 1% of
each other. In this case, the system will calculate the capacitance value that minimizes
velocity variations. When the balance calibration procedure is completed, bit 7 of UDC
register 201/1201 will be set, and the balance value will be stored in RES_BAL%. If
the sine/cosine magnitudes are not within 5% of each other, bit 5 of UDC register
203/1203 (Tuning Aborted Warning) will also be set.
Checking Calibration Procedure Results
As described previously, bits 6 and 7 of UDC register 201/1201 will be set to indicate
the gain and balance calibration procedures, respectively, have been completed.
These bits do not indicate that the procedures were successful or that the resulting
values are valid. After each test, check the value stored in the local tunables
RES_GAN% and RES_BAL%. If either value is near or at its maximum value, it may
indicate a problem.
After the balance test, check the Tuning Aborted Warning bit (bit 5, UDC register
203/1203). This bit will be set if the balance calibration procedure was unsuccessful or
yielded unexpected results. Failures may be caused by leaving the resolver
unconnected during the procedure or using cable runs beyond the recommended
lengths (refer to table 4.4). Calibration procedure failures will not prevent the operation
of the drive.
Refer to the SA500 Drive Configuration and Programming instruction manual (S-3044)
for more information about these local tunables.
4.6.1.2 Resolver Alignment
Resolver alignment is required for SA500 drives controlling brushless motors. The
alignment procedure automatically determines the offset required to bring the rotor
and stator fields in the motor 90° apart. This procedure will cause the motor to
move less than one revolution in both the forward and reverse directions for
less than one minute. Uncouple the motor from the load to run this test if this
motion could cause personal injury or would be harmful to your machine.
Note that this procedure should be performed at the lesser of the following two values:
• Rated motor current, or
• 70% of the Power Module rated current