Yaskawa Matrix Converter - Manual (Page 264)

Individual Functions
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99
Suppressing Long-Cycle Oscillation
If oscillation occurs with a longer cycle than the integral time (I) set value, the integral operation is set too
high. Lengthen the integral time (I) to suppress the oscillation.
Suppressing Short Cycle Oscillation
The differential operation is probably set too high if oscillation still occurs when the oscillation cycle is both
relatively short and almost identical to the derivative time (D). Shorten the derivative time (D) to suppress any
mechanical oscillation.
If oscillation continues even when the derivative time (D) is set to 0.00 (D control disabled), reduce the pro-
portional gain (P), or increase the PID primary delay time constant.
„ Setting Precautions
• In PID control, parameter b5-04 is used to prevent the calculated integral control value from exceeding the
specified amount. When the load varies rapidly, the machine may be damaged or the motor may stall in
based on the response of the MxC. In this case, reduce the set value to speed up MxC response.
• The b5-06 parameter is used to prevent the arithmetic operation following the PID control calculations
from exceeding the specified amount. Set this parameter as a percent of the maximum output frequency.
• The b5-07 parameter is used to adjust PID control offset. Set in increments of 0.1% with the maximum
output frequency as 100%.
• Set the low pass filter time constant for the PID control output in b5-08. Enable this parameter to prevent
machinery resonance from occurring when machinery adhesive abrasion is great, or rigidity is poor. In this
case, set the parameter to be greater than the resonance frequency cycle. Increase this time constant to
reduce MxC responsiveness.
• Using b5-09, the PID output polarity can be inverted. Consequently, if the PID target value is increased,
this parameter can be applied to applications to lower the MxC output frequency.
• Using b5-10, gain can be applied to the PID control output. Enable this parameter to adjust the amount of
compensation if adding PID control output to the frequency reference as compensation.
• When PID control output is negative, use parameter b5-11 to invert the MxC. When b1-04 (Reverse Oper-
ation Selection) is set to 1 (enabled), however, PID output limit is 0.
• With the MxC, by setting an independent accel/decel time in parameter b5-17, the PID target value can be
increased or decreased using the accel/decel time. The accel/decel function (parameter C1) used normally,
however, is allocated after PID control, so depending on the settings, resonance with PID control and hunt-
ing in the machinery may occur. If this happens, reduce parameter C1 until hunting does not occur, and
maintain the accel/decel time using b5-17. Also, the set value can be disabled in b5-17 from the external
terminals during run using multi-function input set value 34 (PID soft starter).
Response Before adjustment
After adjustment
Time
Response
Before adjustment
After adjustment
Time