Mitsubishi Electric 800 Series Instruction Manual page 560

5.13.11 Regeneration avoidance function
The regenerative status can be avoided by detecting the regenerative status and raising the frequency.
• Continuous operation is possible by increasing the frequency automatically so it will not go into regenerative operation
even when the fan is turned forcefully by other fans in the same duct.
Pr. Name
882 Regeneration avoidance
G120 operation selection
883 Regeneration avoidance
G121 operation level
884 Regeneration avoidance at
G122 deceleration detection
sensitivity
885 Regeneration avoidance
G123 compensation frequency
limit value
886 Regeneration avoidance
G124 voltage gain
665 Regeneration avoidance
G125 frequency gain
 What is regeneration avoidance operation? (Pr.882, Pr.883)
• When the regenerative status is large, DC bus voltage will rise, which may cause overvoltage alarm (E.OV[]). Regenerative
status can be avoided by detecting this rise of bus voltage, and raising the frequency when the bus voltage level exceeds
Pr.883 Regeneration avoidance operation level.
• The regeneration avoidance operation can be selected to operate constantly or operate only during constant speed.
• The regeneration avoidance function is enabled by setting to Pr.882 Regeneration avoidance operation selection = "1,
2".
Regeneration avoidance operation
example for acceleration
Pr. 883
During regeneration
avoidance function operation
Initial value Setting range
0 0
1
2
940 VDC 300 to 1200 V
0 0
1 to 5
6 Hz 0 to 590 Hz
9999
100% 0 to 200%
100% 0 to 200%
Regeneration avoidance operation
example for constant speed
Pr. 883
Time
During regeneration
avoidance function operation
Time
Description
Disables regeneration avoidance function
Constantly enables regeneration avoidance function
Enables regeneration avoidance function only during
constant-speed operation
Set the bus voltage level to operate the regeneration
avoidance operation. When the bus voltage level is set low, it
will be harder to generate overvoltage error, but actual
deceleration time will be longer.
Set the setting value higher than power supply voltage 
Disables regeneration avoidance due to bus voltage change
rate
Set the sensitivity to detect the bus voltage change rate
Setting value 1 (detection sensitivity: low) to 5 (detection
sensitivity: high)
Set the limit value for frequency to rise when the regeneration
avoidance function operates.
Disables frequency limit
Adjust the response at the time of regeneration avoidance
operation. When the setting value is set larger, response
against the bus voltage change will improve, but the output
frequency may become unstable.
When the vibration cannot be stabilized even if the setting
value of Pr.886 is made smaller, set the setting value of
Pr.665 smaller.
Regeneration avoidance operation
example for deceleration
Pr. 883
Time
During regeneration
avoidance function operation
Time
5.13 (G) Control parameters
3
4
5
5
√ . 5
2
6
7
8
9
10
Time
Time
559
5. PARAMETERS