The “Control Gain” screen consists of a single tab labeled “Control Gain”. Click the “Gain” button (3) in order to access the “Control Gain” screen or click “Screens” on the menu bar and click “Control Gain”.
Control Gain Tab
g01009752
Illustration 26
Proportional Gain Kp – This setting selects the
proportional constant stability parameter. The voltage regulator supplies a value that is equivalent to Kp multiplied by the error between the voltage set point and the actual generator output voltage. Kp values of 0 to 1,000 may be entered in increments of 0.01. If the transient response has too much overshoot, then Kp may be decreased. If the transient response is too slow, then Kp may be increased.
Integral Gain Ki – This setting selects the integral
constant stability parameter. The voltage regulator supplies a value that is equivalent to Ki multiplied by the integral of the error between the voltage set point and the actual generator output voltage. Ki values of 0 to 1,000 may be entered in increments of 0.01.
Increasing the value of Ki decreases the time required to reach steady state.
Derivative Gain Kd – This setting selects the
derivative constant stability parameter. The voltage regulator provides an output value that is equivalent to Kd multiplied by the derivative of the error between the voltage set point and the actual generator output voltage. Kd values of 0 to 1,000 may be entered in increments of 0.01.
Increasing the value of Kd reduces transient response ringing.
Noise Filter Time Constant Td – This setting
selects the noise filter time constant and is used in order to reduce high frequency noise. Values of 0.00 to 1.00 may be entered in increments of 0.01.
Loop Gain Kg – This setting adjusts the loop-gain
level of the PID algorithm. Loop gain values of 0 to 1,000 may be entered in increments of 0.01. Loop gain Kg is an overall gain multiplier affecting all gain parameters, and should be used as a first gain adjustment. Increasing loop gain may be used to increase transient response and reduce time to steady state. Decreasing loop gain will reduce overshoot but will lengthen time to steady state. For self excited machines, a low value may be required for stability. This value may be as low as 5. Refer to the “Poor Voltage Regulation - Troubleshoot” section.
VAR Integral Gain Ki – This setting adjusts the
integral gain and determines the characteristic of the voltage regulator dynamic response to a changed VAR setting. Ki values of 0 to 1,000 may be entered in increments of 0.01.
VAR Loop Gain Kg – This setting adjusts the loop
gain level of the PI algorithm for VAR control. Values of 0 to 1,000 may be entered in increments of 0.01.
PF Integral Gain Ki – This setting adjusts the
integral gain and determines the characteristic of the voltage regulator dynamic response to a changed power factor setting. Values of 0 to 1,000 may be entered in increments of 0.01.
PF Loop Gain Kg – This setting adjusts the loop
gain level of the PI algorithm for power factor control. Values of 0 to 1,000 may be entered in increments of 0.01.
PID Pre-Settings – One of 20 preset stability ranges
within the voltage regulator can be selected from this pull down menu. Selection of one of the 20 preset stability ranges disables the “Proportional Gain” (Kp), “Integral Gain” (Ki), and “Derivative Gain” (Kd) settings of the “Control Gain” tab. Selecting “Custom PID Settings” from the “PID Pre-Settings” menu enables the Kp, Ki, and Kd settings. Caterpillar does not recommend using the current “PID Pre-Settings” in the list except the “Custom PID Settings”. The default settings from the “Custom PID Settings” will work well for most SR4 and SR4B generator applications. If an adjustment is to be made, the “Loop Gain Kg” should be used as a first adjustment approach.
“PID” Button – Press the PID button in order to
open the PID “Calculator” screen. See illustration 27. The PID “Calculator” is used in order to calculate proportional gain (Kp), integral gain (Ki), and derivative gain (Kd) for a PID type controller. The generator and the exciter time constant values are entered into the “PID Calculator” in order to calculate these values. AVR overall gain (Kg) and derivative filter time constant (Td) can be entered and saved in a file. Refer to the “PID Calculator” section for additional information.
PID Calculator
g01009819
Illustration 27
The PID parameters are calculated for the desired system response with a settling time of about one third of the generator time constant and about 10 percent overshoot.
Excitation Control Data
Gen. Information – Up to 20 characters of
descriptive text for the generator can be entered in this field. When a PID record is created, this text identifies the record.
Gen Time Constant (T'do) - (Seconds) – The open
circuit generator time constant (T'do) can be selected from this pull down menu. Time constant values of 1 to 15 seconds can be entered in 0.05 second increments.
Note: Values for specific generators can be obtained
from the “Technical Marketing Information System”.
Exciter Time Constant (Te) - (Seconds) – The
exciter time constant (Te) can be selected from this pull down menu. The value displayed in this menu depend on the generator time constant (T'do) that is selected. Available values range from one fifth to one half of (T'do) in 0.01 second increments. The maximum possible exciter time constant is 3 seconds.
Default Exciter Time Constant – When this box
is checked, manual selection of the exciter time constant is disabled and Te is set at one-sixth the value of the generator time constant (T'do). This is not recommended for SR4 and SR4B generators.
AVR Control Parameters
Proportional Gain (Kp) – This is a read only value.
The value is calculated from the values that are selected from the generator time constant (T'do) and exciter time constant (Te) pull down menus.
Integral Gain (Ki) – This is a read only value. The
value is calculated from the values that are selected from the generator time constant (T'do) and exciter time constant (Te) pull down menus.
Derivative Gain (Kd) – This is a read-only value.
The value is calculated from the values selected from the generator time constant (T'do) and exciter time constant (Te) pull down menus.
Time Constant (Td) – The time constant value
entered in this field is used to reduce high frequency noise. The Td value entered is recommended to be less than 0.2 (Kd, Kp). Td values from zero to 1.00 may be entered in 0.01 increments. Entering a value of “zero” disables the filtering.
AVR Overall Gain (Kg) – The AVR overall gain is
entered in this field. A Kg value of zero to 1000.00 may be entered. Note: If the “Update CDVR PC Software” button is pressed, a default value of 1.00 is loaded into this field. Make sure to adjust this value as needed.
PID Record List
This area of the PID “Calculator” screen lists all of the saved PID records that are available.
Remove Record Button – Records in the “PID
Record List” can be selected and deleted by clicking this button.
Add Record Button – A record containing the
excitation control data and AVR control parameters can be added to the “PID Record List” by clicking this button. The “Save” button must be pressed in order to save the record in the list.
Update CAT PC Software Button – Transfers
the AVR control parameters calculated in the PID calculator and recorded to the “Control Gain” screen.
Close Button – Clicking this button closes the “PID
Table 9
Power Input to Voltage Regulator (PM /
SE / IE systems) Power Input to Exciter
Nominal Requirements RequirementsFull Forcing SE/PM
Voltage RegulatorInput to FrequencyRange
Number of Phases Exciter Nominal Voltage Input Exciter Nominal Current Input Exciter Resistance Exciter Time Constant Te Full Forcing Voltage Full Forcing Current Kato 2600/ 2700 Frame PM 70to
105V 240 Hz 3 35V 10A 3.7 ohms 0.22 sec 65V 15A
Kato 2800
Frame PM 120V 90 Hz 1 50V 5A 10 ohms 0.18 sec 90V 10A
6100 PM 140V 120 Hz 3 40V 4A 10 ohms 0.22 sec 60V 10A
6100 SE 140V 60 Hz 1 40V 4A 10 ohms 0.22 sec 60V 10A
6100 IE 140V 50/180 Hz 2x1 40V 4A 10 ohms 0.22 sec 60V 10A
1400
/4P PM 180V 200/240 Hz 3 45V 4.5A 11 ohms 0.06 sec 80V 10A
1400
/4P IE 140V 50/180 Hz 2x1 45V 4.5A 10 ohms 0.06 sec 80V 10A
1600
/4P PM 180V 200/240 Hz 3 60V 6A 10 ohms 0.094 sec 150V 15A
1600
/4P IE 240 V 50/180 Hz 2x1 60V 6A 10 ohms 0.094 sec 150V 15A
1800
/4P PM 180V 240 Hz 3 84V 4A 11 ohms 0.26 sec 190V 8.5A
1800
/4P AREP 240V 60 Hz 1 84V 4A 11 ohms 0.26 sec 190V 8.5A
SR4/
SR4B PM
70 to 105V
240 Hz 3 35V 10A 3.7 ohms 0.22 sec 65V 15A
SR4/
SR4B SE 240V 60 Hz 1 35V 10A 3.7 ohms 0.22 sec 65V 15A