Mitsubishi Electric FR-A800 Series Instruction Manual page 735

 Detecting the regenerative status faster during deceleration (Pr.884)
• Since a rapid change in bus voltage cannot be handled by bus voltage level detection during the regeneration avoidance
operation, deceleration is stopped by detecting the change in bus voltage and if it is equal to or lower than Pr.883
Regeneration avoidance operation level. Set the detectable bus voltage change rate as the detection sensitivity in
Pr.884 Regeneration avoidance at deceleration detection sensitivity. A larger set value increases the detection
sensitivity.
NOTE
• When the setting value is too small (detection sensitivity is not good), detection will not be possible, and regeneration
avoidance will operate even with the bus voltage change caused by a change in the input power.
 Limiting the regeneration avoidance operation frequency (Pr.885)
• It is possible to assign a limit to the output frequency corrected (rise) by the regeneration avoidance operation.
• Limit of the frequency is output frequency (frequency before regeneration avoidance operation) + Pr.885 Regeneration
avoidance compensation frequency limit value for during acceleration and constant speed. During deceleration, when
the frequency increases due to the regeneration avoidance operation and exceeds the limit value, the limit value will be
retained until the output frequency is reduced to be the half the Pr.885 setting.
• When the frequency that have increased by the regeneration avoidance operation exceeds Pr.1 Maximum frequency, it
will be limited to the maximum frequency.
• When Pr.885 = "9999", the regeneration avoidance compensation frequency limit is disabled.
• Set the frequency around the motor rated slip frequency. Increase the setting value if the overvoltage protection function
(E.OV[]) is activated at the start of deceleration.
Rated motor slip frequency =
 Adjusting the regeneration avoidance operation (Pr.665, Pr.886)
• If the frequency becomes unstable during regeneration avoidance operation, decrease the setting of Pr.886 Regeneration
avoidance voltage gain. On the other hand, if an overvoltage fault occurs due to a sudden regeneration, increase the
setting.
• If setting a smaller value in Pr.886 does not suppress the vibration, set a smaller value in Pr.665 Regeneration avoidance
frequency gain.
NOTE
• During the regeneration avoidance operation, the stall prevention (overvoltage) "oL" is displayed and the Overload warning
(OL) signal is output. Set the operation pattern at an OL signal output using Pr.156 Stall prevention operation selection.
Use Pr.157 OL signal output timer to set the OL signal output timing.
• The stall prevention is enabled even during regeneration avoidance operation.
• The regeneration avoidance function cannot decrease the actual deceleration time for the motor to stop. Since the actual
deceleration time is determined by the regenerative power consumption performance, consider using a regeneration unit (FR-
BU2, BU, FR-BU, FR-CV, FR-HC2, or FR-XC) or a brake resistor (such as the FR-ABR) to decrease the deceleration time.
• When using a regeneration unit (FR-BU2, BU, FR-BU, FR-CV, FR-HC2, or FR-XC) or a brake resistor (such as the FR-ABR)
to consume the regenerative power at constant speed, set Pr.882 = "0 (initial value)" (the regeneration avoidance function is
disabled). When consuming the regenerative power at the time of deceleration with the regeneration unit, etc., set Pr.882 =
"2" (enables regeneration avoidance function only at the constant speed).
• When using the regeneration avoidance function under Vector control, noise may be generated from the motor during
deceleration. In such case, adjust the gain by performing easy gain tuning, etc. (Refer to
734
5. PARAMETERS
5.16 (G) Control parameters
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Synchronized speed at the time of base frequency – rated rotation speed
Synchronized speed at the time of base frequency
Limit level
Output frequency (Hz)
Pr.885
Pr.885/2
Time
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× Rated motor frequency
page 254.)