Mitsubishi Electric 800 Series Instruction Manual (Function page 235

 Control block diagram
(Pr.16)
Acceleration and
deceleration time
(Pr.7, Pr.8)
Second acceleration and
deceleration time
(Pr.44, Pr.45)
Acceleration and
deceleration time
in low-speed range
(Pr.791, Pr.792)
 Acceleration time setting (Pr.7, Pr.20)
• Use Pr.7 Acceleration time to set the acceleration time required to change the frequency to the frequency set in Pr.20
Acceleration/deceleration reference frequency from stop status.
• Set the acceleration time according to the following formula.
Acceleration time setting = Pr.20 setting × (Acceleration time to change the frequency from stop status to maximum
frequency) / (Maximum frequency - Pr.13 setting)
• For example, the following calculation is performed to find the setting value for Pr.7 when increasing the output frequency
to the maximum frequency of 50 Hz in 10 seconds with Pr.20 = 60 Hz (initial value) and Pr.13 = 0.5 Hz.
Pr.7 setting = 60 Hz × 10 s / (50 Hz - 0.5 Hz) ≈ 12.1 s
Pr.20
(60Hz/50Hz)
Acceleration Pr.7
time Pr.44
 Deceleration time setting (Pr.8, Pr.20)
• Use Pr.8 Deceleration time to set the deceleration time required to change the frequency to a stop status from the
frequency set in Pr.20 Acceleration/deceleration reference frequency.
• Set the deceleration time according to the following formula.
Deceleration time setting = Pr.20 × deceleration time from maximum frequency to stop / (maximum frequency - Pr.10)
• For example, the following calculation is used to find the setting value for Pr.8 when decreasing the output frequency from
the maximum frequency of 50 Hz in 10 seconds with Pr.20 = 120 Hz and Pr.10 = 3 Hz.
Pr.8 setting = 120 Hz × 10 s / (50 Hz - 3 Hz) ≈ 25.5 s
NOTE
• If the acceleration/deceleration time is set, the actual motor acceleration/deceleration time cannot be made shorter than the
shortest acceleration/deceleration time determined by the mechanical system J (moment of inertia) and motor torque.
• If the Pr.20 setting is changed, the settings of Pr.125 and Pr.126 (frequency setting signal gain frequency) do not change.
Set Pr.125 and Pr.126 to adjust the gains.
• Under PM sensorless vector control, if the protective function (E.OLT) is activated due to insufficient torque in the low-speed
range, set longer acceleration/deceleration times only in the low-speed range in Pr.791 Acceleration time in low-speed
range and Pr.792 Deceleration time in low-speed range.
234
10. (F) Settings for Acceleration/Deceleration
10.1 Setting the acceleration and deceleration time
JOG
Output frequency Pr.147
(or Pr.147= "9999" )
Output frequency Pr.147
Set
frequency
Time
Deceleration
Pr.8
time
Pr.45
Output frequency 10% of the rated motor frequency
JOG-ON
RT-OFF
JOG-OFF
RT-ON
Output frequency 10% of the rated motor frequency
Acceleration time
or
deceleration time