TWO-SPEED RESOLVER CALIBRATION
APPENDIX C - TWO-SPEED RESOLVER CALIBRATION
1.0 Introduction
This appendix contains instructions for calibrating the two-speed resolvers (two-
speed resolver option only) in the 7200 ACS.
2.0 Setting Excitation Voltage
The two-speed system used on the 7200 ACU is stable to within +/-0.0005
degrees, hence bobble in the last one one-thousandth position may be present, but
only by one count. An excessive bobble of more than 0.001 degree is usually
caused by either poor or insufficient environmental shielding or low excitation
voltage (providing there are no mechanical problems). The following procedures
describe how to check the excitation voltage; shielding is discussed in Appendix E,
Troubleshooting Guide Paragraph 5.0, of this manual.
1. Turn off the power to the 7200 ACU and slide it forward from the rack.
Remove the four #6-32 screws holding the front of the top lid and lift the lid,
locking it in place with the hinge found on the right side of the sub-rack inside
the unit.
2. Power up the unit and disable the drives using the front DRIVE ENABLE switch
as a precautionary measure. Locate the small blue trimpot on the left side of
the 800225-05 RDC card. This trimpot adjusts the resolver excitation voltage
level which can be measured at J7 (EL) or J8 (AZ) on the backpanel between
pin 2 (R1, +Ref) and pin 8 (R2, GND).
3. Use an AC RMS voltmeter to set the voltage to at least 4 V RMS. If the
bobble persists, raise the voltage up to a maximum of 9 V RMS. This should
correct the problem on standard run lengths. If the bobble persists or does
not diminish, a bad shield or signal wire connection may be the problem.
4. Re-enable the drives, and verify that no drive cabinet related errors are
occurring. Resecure the top lid, slide unit back in rack, and resecure the unit
using the #10-24 cup head screws.
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