Chapter 2. Troubleshooting
69
Offset Balance Adjustments
The offset balance potentiometer (offset pot) adjusts the offset voltage of the APEX615n’s
internal command signal. The offset is zeroed at the factory, with the pot set near the middle of
its range of travel. Normally, you do not need to adjust it. However, if you suspect the pot’s
setting has been altered, the procedure below will explain how to adjust it to zero the offset
balance.
NOTE
This procedure—adjusting the offset balance potentiometer—was performed at the factory. If
yours is a new APEX615n, you do not need to perform this step. You can use the default
factory settings.
A small offset will not normally cause a problem—the APEX615n’s internal controller can
automatically compensate for any offset. If the offset is excessive, though, you may notice
that the motor reaches a higher speed in one direction than the other. If this causes a problem
in your application, follow the procedure below to zero the offset.
1. Remove the load from the motor. The motor’s shaft must be free to turn.
2. Turn on AC power to the APEX615n.
3. Disable hardwired limits: (LHØ)
4. Disable monitoring of maximum allowable position error: (SMPERØ)
5. Set all servo gains to zero: (SGPØ, SGIØ, SGVØ, SGAFØ, SGVFØ)
CAUTION
If there is little or no load on the motor shaft, any internal offset may cause an acceleration to a
high speed.
6. Set the commanded offset voltage to zero: (SOFFSØ)
7. Enable the drive with the DRIVE1 command.
8. With all gains set to zero, the APEX615n is now operating open loop. Any motion of
the motor shaft is due to an internal offset. You can measure the offset by connecting a
digital volt meter (DVM) to the Torque Cmd Test Point test point, as shown below.
Connect the probe’s negative lead to any of the GND terminals on the Drive Auxiliary
connector.
APEX6151
Enable
Disable
Bridge Fault
Torque Cmd
Test Point
Offset
Balance
Tach Output
Calibration
The offset voltage should be
very close to ØV. If it is not,
zero the offset by turning the
Offset Balance pot. This is a
15-turn pot, located on the
front panel of the APEX615n.
The null position—where the
voltage approaches zero, and
the motor stops turning—will
be near the center of the pot’s
range of travel.
When you have zeroed the offset voltage, and the motor stops turning, this procedure is
complete.
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