Speed Does Not Accelerate - Mitsubishi Electric FR-D720S SC EC Instruction Manual

Troubleshooting
7.6.12

Speed does not accelerate

Check points Possible Cause
Input signal
Parameter
Setting
Main Circuit
FR-D700 SC EC
Start command and frequency command
are chattering.
The wiring length used for analog fre-
quency 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.
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 when V/f control is
performed. (Pr. 3, Pr. 14, Pr. 19)
Stall prevention is activated due to a heavy
load.
Auto tuning is not performed under Gen-
eral-purpose magnetic flux vector control.
During PID control, output frequency is automatically controlled to make measured
value = set point.
Brake resistor is connected between ter-
minal P/+ and P1 by mistake.
Check first when you have troubles
Countermeasures
Check if the start command and the fre-
quency 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.
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.
Reduce the load weight.
Set Pr. 22 "Stall prevention operation
level" higher according to the load. (Set-
ting Pr. 22 too large may result in frequent
overcurrent trip (E.OC ).)
Check the capacities of the inverter and
the motor.
Perform offline auto tuning.
Connect an optional brake transistor (FR-
ABR) between terminal P/+ and PR.
Refer to
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