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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.
(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
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.
(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
regeneration avoidance operation) + Pr. 885 Regeneration avoidance
compensation frequency limit value during acceleration or constant
speed. If the frequency increased by regeneration avoidance
function exceeds the limit value during deceleration, the limit value
is held until the output frequency falls to 1/2 of Pr. 885.
⋅ When the frequency increased by regeneration avoidance function
has reached Pr. 1 Maximum frequency, it is limited to the maximum
frequency.
⋅ When Pr. 885="9999," the regeneration avoidance compensation
frequency limit is disabled.
CAUTION
⋅ When regeneration avoidance operation is performed, (overvoltage stall) is displayed and the OL signal is output. Set the
operation pattern at an OL signal output using Pr.156 Stall prevention operation selection. Set the output timing of the OL signal
using Pr.157 OL signal output timer.
⋅ When regeneration avoidance operation is performed, stall prevention is also activated.
⋅ The regeneration avoidance function cannot shorten the actual deceleration time taken to stop the motor. The actual
deceleration time depends on the regeneration energy consumption 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.) to consume regeneration energy at constant speed.
⋅ 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 using the regeneration unit, etc. to consume
regeneration energy at deceleration, set Pr. 882 to "2" (regeneration avoidance function valid only at a constant speed).
⋅ 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 105)
♦ Parameters referred to ♦
Pr. 1 Maximum frequency Refer to page 157
Pr. 8 Deceleration time Refer to page 172
Pr. 22 Stall prevention operation level Refer to page 152
Limit level
Time
Pr.885
Output frequency (Hz)
Pr.885/2
Output
frequency(Hz)