Mitsubishi Electric 800 Series Instruction Manual page 616

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 will be approximately 813 VDC in case of input voltage of 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 at the time of no regenerative status.
• The stall prevention (overvoltage) (oL) will only operate during deceleration, stopping the lowering of output frequency, but on
the other hand, the regeneration avoidance function will constantly operate (Pr.882 = "1") or operate only at constant speed
(Pr.882 = "2"), and raise the frequency depending on the amount of regeneration.
• When the motor becomes unstable due to operation of the stall prevention (overcurrent) (OL) during the regeneration
avoidance operation, increase the deceleration time or lower the setting of Pr.883.
• Under position control, the regeneration avoidance function is not activated.
To detect the regenerative status during deceleration faster (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 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.
Limit 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.
• By setting to Pr.885 = "9999", regeneration avoidance operation frequency limitation is disabled.
• Set using the motor rated slip frequency as a guideline. Raise the setting value if the overvoltage protection function
(E.OV[]) operation at the start of deceleration.
Rated motor slip frequency =
Limit level
Pr.885
Synchronized speed at the
time of base frequency
Synchronized speed at the time of base frequency
Output frequency (Hz)
Pr.885/2
Time
2 times of the normal input voltage.
- rated rotation speed
 Rated motor frequency
(G) Control parameters
615
PARAMETERS
5
GROUP
G