Mitsubishi Electric 800 Series Instruction Manual page 593

6.5.12 Speed does not accelerate
Check
points
Input signal 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.
The input signal lines are affected by external
EMI.
Parameter Pr.1 Maximum frequency, Pr.2 Minimum
setting frequency, Pr.18 High speed maximum
frequency, and Pr.902 to Pr.905 settings are
improper.
The maximum voltage (current) input value is
not set during the External operation. (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 when V/F control is
performed.
(Pr.3, Pr.14, Pr.19)
Stall prevention function is activated due to a
heavy load.
Auto tuning is not performed under Advanced
magnetic flux vector control.
The setting of pulse train input is improper.
During PID control, output frequency is automatically controlled to make measured value = set point.
592
6. PROTECTIVE FUNCTIONS
6.5 Check first when you have a trouble
Possible cause Countermeasure
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 and Pr.2 and set Pr.18.
Check the Pr.902 to Pr.905 settings.
Check the settings of Pr.125 Terminal 2 frequency setting
gain frequency and Pr.126 Terminal 4 frequency setting
gain frequency.
To operate at 120 Hz or higher, set Pr.18 High speed
maximum frequency.
Increase/decrease the 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 frequency voltage to set the base voltage (for
example, 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. (If Pr.22 is set too high, an overcurrent trip (E.OC[]) is
likely to occur.)
Check the capacities of the inverter and the motor.
Perform offline auto tuning.
Check the specification of the pulse generator (open collector
output or complementary output) and check the adjustment of
the pulse train and frequency (Pr.385 Frequency for zero
input pulse and Pr.386 Frequency for maximum input
pulse).
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253
328
253, 328
538
539
541
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257
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