CONTREX CXB2040 - Manual (Page 35)

CXB1525 and CXB2040 MANUAL
8900 Zachary Lane N., Maple Grove, MN 55369 U.S.A. 32
The purpose of the following procedure is to set the system bandwidth to obtain a critically-damped
response with the maximum possible tach gain. There are many possible settings of Tach Gain and
Compensation which will yield a critically damped waveform. The optimum setting will occur when the
Tach Gain is as CW as possible and the Compensation is as CCW as possible.
However, the servo-loop may become unstable (the motor oscillates or hunts) with a very low (near
CCW) setting of Compensation. In this case, stability is the limiting factor. At no time should the servo-
loop be allowed to be unstable.
Amplifiers are normally shipped with the Tach Gain (RV4) set at 75%. This is a good place to start.
If you are unsure of where the Tach Gain is set, turn the Tach Gain fully CW (up to 12 turns), then CCW 3
turns.
6. Move the oscilloscope to the TACH OUT (J1-5), set the battery box for a steady DC voltage
and adjust the input voltage or Signal 2 gain for about 400RPM.
7. Pulse the input and compare the waveform with figure 6.1.
8. Adjust the Compensation pot CCW until the waveform is critically damped or one hook overshoot.
Then proceed to step 10.
9 If the desired waveform cannot be obtained by adjusting the Compensation pot, back off (CCW) the
Tach Gain pot a few turns and repeat step 8.
10. Do not adjust the Tach Gain or Compensation pots for the rest of the calibration procedure.
11. With the battery box still connected at J1-3 and J1-4 for single-ended input (or if your system uses the
differential input, move battery box to J1-1 and J1-2), set battery box for a known DC voltage. Adjust
Signal 1 Gain (RV3) or (RV2 for differential input) to obtain the desired motor velocity.
12. If the motor is rotating the wrong direction for a given input polarity, turn the Loop Gain pot full
CCW. Switch MTR REVERSE (S1-4) from OFF to ON (or vice-versa). Turn the Loop Gain pot back
to full CW.
13. Remove the battery box, and repeat only step 4.
14. Calibration complete. Reconnect signal wires.
NOTE: All pots except the Loop Gain are 12-turn. See Section 5.3.2 for current mode
configuration.
1. Turn the current limit (RV7) to mid position and the Loop Gain (RV8) full CCW.
2. Apply main power and fan power. Slowly turn the Loop Gain (RV8) full CW. Motor should be
stopped or turning slowly.
3. Set Balance (RV5) for 0V at ABS I (J1-7).
6.3.3 Sine/Resolver Mode Amplifier Calibration - Current Mode: