YASKAWA Varispeed E7 Instruction Manual And Parameter Description page 225

Suppressing Short Cycle Vibration
If short cycle vibration occurs reduce the proportional gain (P), or increase the PI primary delay time constant.
Setting Precautions
In PI control, the b5-04 constant is used to prevent the calculated integral control value from exceeding a
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specified amount. When the load varies rapidly, the Inverter response is delayed, and the machine might
get be damaged or the motor may stall. In this case, reduce the set value to speed up Inverter response.
The b5-06 constant is used to prevent the output value of the the PI control calculation from exceeding a
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specified amount. The value is set taking the maximum output frequency as 100%.
The b5-07 constant is used to adjust PI control offset. The value is set in increments of 0.1%, taking the
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maximum output frequency to be 100%. Normally it is added to the PI output value. If differential PI feed-
back is selected (H3-09=16), it is added to the difference between both feedback values.
Set the filter time constant for the PI control output in b5-08 to prevent machinery resonance when
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machinery friction is great, or rigidity is poor. In this case, set the constant to be higher than the resonance
frequency cycle duration. Increase this time constant to reduce Inverter responsiveness.
Using b5-09, the PI output polarity can be inverted. If now the PI target value increases the output fre-
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quency will be lowered. This function is usable e.g. for vacuum pumps.
Using b5-10 a gain can be applied to the PI control output. Enable this constant to adjust the amount of
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compensation if adding PI control output to the frequency reference as compensation (b5-01 = 3).
When PI control output is negative, you can use constant b5-11 to determine what happens to the inverter
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output. When b1-04 (Prohibition of Reverse Operation) is set to 1 or 3 (enabled), however, the PI output is
limited to 0.
Using the b5-17 constant the PI target value can be raised or lowered with an accel./decel. ramp function
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(PI soft starter).
The normally used accel./decel. function (C1-
ing on the settings, resonance with the PI control and hunting in the machinery may occur. Using b5-17
this behaviour can be prevented.
The PI soft starter function can also be disabled or enabled using a multifunction digital input (H1-
to be set to 34).
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Response
After adjustment
Before adjustment
Time
constants) is allocated after PI control so that, depend-
has