Speed Does Not Accelerate - Mitsubishi Electric FR-F740 EC Instruction Manual

Check first when you have troubles
7.6.12

Speed does not accelerate

Check points Possible cause
Input signal
Parameter
Setting
7 - 34
Start command and frequency command
are chattering.
The wiring length used for analog
frequency command is too long, and it is
causing a voltage (current) drop.
Input signal lines are affected by external
EMI.
Pr. 1, Pr. 2, Pr. 18, calibration parameter
C2 to C7 settings are improper.
The maximum voltage (current) input
value is not set during the external opera-
tion (Pr. 125, Pr. 126, Pr. 18).
Torque boost (Pr. 0, Pr. 46) setting is
improper under V/f control, so the stall
prevention function is activated.
V/f pattern is improper.
(Pr. 3, Pr. 14, Pr. 19)
Stall prevention is activated due to a heavy
load.
During PID control, output frequency is automatically controlled to make measured
value = set point.
Countermeasures
Check if the start command and the
frequency command are correct.
Perform analog input bias/gain calibration.
Take countermeasures against EMI, such
as using shielded wires for input signal
lines.
Check the settings of Pr. 1 "Maximum fre-
quency" and Pr. 2 "Minimum frequency".
If you want to run the motor at 120Hz or
higher, set Pr. 18 "High speed maximum
frequency".
Check the calibration parameter C2 to C7
settings.
Check the Pr. 125 and Pr. 126 settings.
To operate at 120 Hz or higher, set Pr. 18.
Increase/decrease Pr. 0 "Torque boost"
setting value by 0.5% increments so that
stall prevention does not occur.
Set rated frequency of the motor to Pr. 3
"Base frequency". Use Pr. 19 "Base fre-
quency voltage" to set the base voltage
(e.g. rated motor voltage).
Change Pr. 14 "Load pattern selection"
according to the load characteristic.
(V/F control)
Reduce the load weight.
Set Pr. 22 "Stall prevention operation
level" higher according to the load.
(Setting Pr. 22 too large may result in fre-
quent overcurrent trip (E.OC ).)
Check the capacities of the inverter and
the motor.
Troubleshooting
Refer to
page
—
6-199
3-44
6-54
6-199
6-54
6-199
6-39
6-58
6-60
—
6-44
—
6-328