5.2 b: Application
164 YASKAWA ELECTRIC SIEP C710616 27C YASKAWA AC Drive A1000 Technical Manual
■ b8-06: Search Operation Voltage Limit (V/f, V/f w/PG)
Sets the voltage limit for the optimal output voltage detection of Speed Search as a percentage of the maximum output
voltage. During the search operation, the drive will keep the output voltage above this level to prevent motor stalling.
Note: If set too low, the motor may stall with a sudden increase to the load. Disabled when b8-06 = 0. Setting this value to 0 does not
disable Energy Saving.
◆ b9: Zero Servo
The Zero Servo function is a position loop that can be used in CLV and CLV/PM control modes to lock the motor at a
certain position.
It must be activated using a digital input set for H1- = 72. The drive will decelerate when this input is closed. Once
the motor speed falls below the level set in parameter b2-01, the drive goes into the Zero Servo mode and holds the
current position. When the input assigned to trigger the Zero Servo function is released and the Run command is still
present, the drive reaccelerates.
Figure 5. 29
Figure 5.29 Zero Servo Operation
When Zero Servo is active, the deviation between the rotor position and the zero position is displayed in monitor U6-22
(monitor value must be divided by 4 to get the deviation in actual encoder pulses).
A digital output programmed for “Zero Servo complete” (H2- = 72) is turned on when the rotor position is within the
zero position, plus or minus the Zero Servo completion width set in parameter b9-02.
Note: 1. The Run command must remain on when using the Zero Servo function. If the Run command is switched off, then Zero Servo will no
longer be able to hold the load in place.
2. When the Zero Servo command has shut off, the Zero Servo Completion digital output width also shuts off.
3. Avoid using Zero Servo to lock 100% load for long periods, as this can trigger a fault. If such loads need to be held in place for long
periods, either make sure the current is less than 50% of the drive rated current during Zero Servo, or use a larger capacity drive.
4. If the load rotates the motor when using CLV/PM, a dv4 fault may occur. To prevent this, either increase the Zero Servo gain (b9-01)
or increase the number of pulses set to F1-19 that are required to trigger dv4.
■ b9-01: Zero Servo Gain
Parameter b9-01 adjusts the responsiveness of the Zero Servo position loop. Increase the value if the response is too slow
and the deviation from the zero position rises too high when load is applied. Decrease the value if vibrations occur during
Zero Servo operation.
Note: Before adjusting the Zero Servo gain, make sure the ASR parameters (C5-) are set up properly and vibration or hunting does
not occur when running with a zero speed reference.
■ b9-02: Zero Servo Completion Width
Sets the range around zero position within that the Zero Servo complete output signal (H2- = 72) is switched on
during Zero Servo operation. The value in b9-02 must be set to the allowable deviation in actual encoder pulses
multiplied by four.
No. Name Setting Range Default
b8-06 Search Operation Voltage Limit 0 to 100% 0%
No. Name Setting Range Default
b9-01 Zero Servo Gain 0 to 100 5
No. Name Setting Range Default
b9-02 Zero Servo Completion Width 0 to 16383 10
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