Mitsubishi Electric 800 Series Instruction Manual page 402

NOTE
• The slope of frequency rising or lowering by the regeneration avoidance operation will change depending on the regenerative
status.
• The DC bus voltage of the inverter will be approximately
The bus voltage is approx. 311 VDC at an input voltage of 220 VAC (622 VDC at 440 VAC and 813 VDC at 575 VAC).
However, it may vary depending on the input power supply waveform.
• Make sure that the setting value of Pr.883 will not get under DC bus voltage level. The frequency will rise with operation of the
regeneration avoidance function even during operation other than the regenerative operation.
• The stall prevention (overvoltage) (OLV) will be activated only during deceleration, stopping the lowering of output frequency.
On the other hand, the regeneration avoidance function will be activated constantly (Pr.882 = "1") or only at constant speed
(Pr.882 = "2"), and raise the frequency depending on the amount of regeneration.
• When the motor becomes unstable due to the stall prevention (overcurrent) (OLC) during the regeneration avoidance
operation, increase the deceleration time or set a lower value in Pr.883.
 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 =
Limit level
Pr.885
 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) "OLV" 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-XC, FR-CV, FR-HC2) or brake resistor (FR-ABR, etc.) to decrease the deceleration time.
• When using a regeneration unit (FR-BU2, BU, FR-BU, FR-XC, FR-CV, FR-HC2) or brake resistor (FR-ABR, etc.) 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).
Synchronized speed at the time of base frequency – rated rotation speed
Synchronized speed at the time of base frequency
Output frequency (Hz)
Pr.885/2
Time
√
times of the normal input voltage.
2
15.9 Regeneration avoidance function
× Rated motor frequency
401
15.(G) Control Parameters
11
12
13
14
15
16
17
18
19
20