Mitsubishi Electric FR-A740-00023 Instruction Manual page 382

Special operation and frequency control
(2) To detect the regenerative status during deceleration faster (Pr. 884)
⋅ As the regeneration avoidance function cannot respond to an abrupt voltage change by detection of the bus
voltage level, the ratio of bus voltage change is detected to stop deceleration if the bus voltage is less than Pr. 883
Regeneration avoidance operation level.
Set that detectable bus voltage change ratio to Pr. 884 as detection sensitivity.
Increasing the setting raises the detection sensitivity.
CAUTION
Too small setting (low detection sensitivity) will disable detection, and too large setting will turn on the regeneration avoidance
function if the bus voltage is varied by an input power change, etc.
Limit level
Pr.885
(4) Regeneration avoidance function adjustment (Pr. 665, Pr. 886)
⋅ If the frequency becomes unstable during regeneration avoidance operation, decrease the setting of Pr. 886
Regeneration avoidance voltage gain. Reversely, if sudden regeneration causes an overvoltage alarm, increase the
setting.
⋅ When vibration is not suppressed by decreasing the Pr. 886 Regeneration avoidance voltage gain setting, set a smaller
value in Pr. 665 Regeneration avoidance frequency gain.
CAUTION
⋅ When regeneration avoidance operation is performed,
⋅ When regeneration avoidance operation is performed, stall prevention is also activated at the same time.
⋅ The regeneration avoidance function cannot shorten the actual deceleration time taken to stop the motor. The actual
deceleration time depends on the regeneration capability. When shortening the deceleration time, consider using the
regeneration unit (FR-BU2, BU, FR-BU, MT-BU5, FR-CV, FR-HC, MT-HC) or the brake resistor (FR-ABR, etc.).
⋅ When using the regeneration unit (FR-BU2, BU, FR-BU, MT-BU5, FR-CV, FR-HC, MT-HC) or the brake resistor (FR-ABR, etc.),
set Pr. 882 to "0 (initial value)" (regeneration avoidance function invalid).
⋅ When regeneration avoidance operation is performed, the OL signal output item of Pr. 156 also becomes the target of
(overvoltage stall). Pr. 157 OL signal output timer also becomes the target of
⋅ Under vector control, unusual noise may be generated from the motor during deceleration when using regeneration avoidance
function. To prevent this, make gain adjustment, e.g. by performing easy gain tuning. (Refer to page 99)
♦ Parameters referred to ♦
Pr. 1 Maximum frequency
Pr. 8 Deceleration time Refer to page 167
Pr. 22 Stall prevention operation level
372
(3) Limit regeneration avoidance operation frequency (Pr. 885)
You can limit the output frequency compensated for (increased) by
the regeneration avoidance function.
⋅ The frequency is limited to the output frequency (frequency prior to
Output frequency (Hz)
Pr.885/2
Time
⋅ When the regeneration avoidance frequency has reached Pr. 1
⋅ Pr. 885 is set to "9999", the frequency setting is invalid.
Refer to page 151
Refer to page 144
regeneration avoidance operation) + Pr. 885 Regeneration avoidance
compensation frequency limit value during acceleration or constant
speed. If the regeneration avoidance frequency exceeds the limit
value during deceleration, the limit value is held until the output
frequency falls to 1/2 of Pr. 885.
Maximum frequency, it is limited to the maximum frequency.
(overvoltage stall) is displayed and the OL signal is output.
(overvoltage stall).