2-11
MN716
Figure 2-11 Offset Trimpot Adjustment
Figure 2-12 Deadband Trimpot Adjustment
a
(%)
MAIN SPEED
POT
ROTATION
-100
-100
(%) SPEED
100
b
100
c
CURVE OFFSET
(a) None
(b) Forward
(c) Reverse
(%) SPEED
b
-100
-100
b
a
100
100
a
Curve (a): No Deadband
Curve (b): Max. Deadband
Note: If the deadband trimpot is set too low (CCW direction), the motor may oscillate between forward
and reverse. Adjust deadband trimpot CW until the instability disappears. (Oscillation may also
occur due to response setting.
Forward Current Limit (FWD CL) and Reverse Current Limit (REV CL)
Caution: Adjusting the CL above 150% of motor rating can cause overheating and demagnetization of some
PM motors. Consult motor manufacturer.
Sets the maximum DC motor current for both the forward and reverse directions. The amount of DC
current determines the amount of maximum motor torque in both the Speed Control Mode and Torque
Mode. These CL trimpots are factory set at 150% of the motor current. The value can be reduced by
adjustment of the CL trimpots. Some applications require a lower torque limiting value to prevent
damage to the process material or the drive train.
Re-Adjust the CL trimpots as follows:
a. Turn CL trimpot to MIN (CCW) position. Be sure jumper J2 is in proper position approximately equal
to the motor DC ampere rating.
b. Connect in a DC ammeter in series with armature lead. Load shaft of motor in accordance with
application requirements.
c. Apply power; Rotate CL trimpot CW until desired CL setting is reached (factory setting is 1.5 times
rated motor current). Be sure control is in Forward direction for FWD CL trimpot adjustment and
likewise with REV CL.
Note: do not stall motor shaft for more than 2 - 3 seconds, to prevent motor damage.
IR Compensation (IR Comp)
The IR Comp is used to stabilize motor speed under varying loads. If control is in Tach Feedback mode,
the IR Comp should be set to minimum -CCW.
Note: Too much IR Comp will cause unstable (oscillatory) operation.
Re-Adjust the IR Comp trimpot as follows:
a. Run motor at approximately 30-50% of rated speed under no load and measure actual speed.
b. Load motor to rated current. Rotate IR Comp trimpot so that loaded speed is the same as the
unloaded speed measured in the previous step.
Control is now compensated so that minimal speed change will occur over a wide range of motor
loads.
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