300 SERIES USER GUIDE
29
Dynamic Setup Method
Equipment required: Oscilloscope, signal generator (square wave, 1 Hz.)
1. Adjust the Feedback pot CCW until oscillation appears (squealing sound). Turn pot 2 turns
CW. Oscillation should cease.
2. Apply square wave to Reference voltage inputs. Monitor current monitor test point (TP2) with
oscilloscope.
3. Adjust IR comp pot (R51) CCW while monitoring waveform on the oscilloscope.
4. Response time of current to square wave should gradually decrease. Stop turning R51 when
waveform begins to show overshoot.
Notes on IR Compensation
IR compensation works as a form of positive feedback that increases the amplifier output
voltage to compensate for the voltage lost across the motors' internal resistance. If this
compensation is increased too much, the system will oscillate. Correct compensation will
be found as the point where the motor load can be increased, and the motor speed will be
maintained at a relatively constant value. If motor speed increases when a load is
applied, there is too much IR comp, and R51 should be turned CW until speed remains
constant under load. On the other hand, if motor speed decreases too much under load,
turn R51 more CCW until speed is held constant.
If you are in a situation where you cannot apply either of the two methods described
above, you can still adjust IR comp relatively well by simply setting the pots as described
above, and then turning R51 (IR comp) gradually CCW while operating the motor under
changing load conditions. By noting that IR comp is too much, or too little you can find a
setting that compensates best without oscillation and overshoot, or slowing down under
load.
If you have to change the speed of the motor in response to the reference voltage (i.e.,
the voltage-gain) this is done by setting R31 (Voltage feedback pot) with R51 at the fully
CW setting. Once the speed is set correctly, begin adjusting R51 (IR comp) to its best
setting. These two pots will interact, so it is important to set the speed first, and then
adjust the IR comp pot next
When adjustment is complete, continue to cycle the motor under varying load conditions
to confirm the pot settings under all of the anticipated load conditions.
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