COVER 8J8423 - Caterpillar

following steps should be used only to as a guide if the default settings in the CDVR do not give acceptable performance. Each generator installation has requirements that are application-specific.
Starting with the factory defaults (Kp = 200, Ki = 600, Td = 0, and Kg = 50), adjust Kg to achieve the desired response. If that response is not achievable, proceed to Step 2.
Perform a "step of reference" test by recording the generator terminal voltage with a chart recorder or similar device. Limit the step sizes to 5% or less of terminal voltage, that is, from 480 V to 504 V.
If the response is too slow, increase Ki.
If the response is oscillatory or has a large amount of overshoot, decrease Ki or Kd.
If the desired response is still not achievable, proceed to Step 3.
If T'do and Te are known, use the PID calculator in order to obtain the starting PID values. If T'do, is known, but Te is not known, use the PID calculator with the default exciter time constant (Te = T'do/6). If the desired response is not obtainable with these PID values, proceed to Step 4.
Start with Kp = 10, Ki = 2, Kd = 2, Td = 0, and Kg = 30. If the voltage set point is not achieved, increase Kg until the machine terminal voltage is equal to the set value. Reduce Ki to 0.01. The terminal voltage should decrease. Adjust Kg in order to obtain 90% of set terminal voltage, for example, if the voltage set point is 480 V, adjust Kg to achieve 432 V.
With Kg set as determined in Step 4, set Kp = 40, Ki = 10, Kd = 10, and Td = 0. Perform a "step of reference" test, with no more than 5% per step, for example, from 480V to 504V. Adjust Kp to achieve 80% of the final value (403V in the example) in the desired time frame. The desired rise time should be based on how fast you want the combined generator and CDVR to respond. In most applications, the rise time will be in the range of 0.5 seconds to 1 second. Once Kp is adjusted, increase Ki in order to get the desired response. If overshoot or if ringing occurs, reduce Ki and then increase Kp, Ki, and Kd. Keep the ratio constant.Note: Many people use a load application or rejection test in order to adjust the voltage regulator. If available, use an inductive load. A resistive load is not the best way to adjust the PID value for a voltage regulator. If the only load available is a resistive load, the user must be aware of the effect upon the system. The performance of the voltage regulator will be effected by the governor for the engine or the response of the speed governor.