Mitsubishi Electric 800 Series Instruction Manual page 591

6.5.7 Acceleration/deceleration is not smooth
Check
points
Parameter Acceleration/deceleration time is too short.
setting
Torque boost (Pr.0, Pr.46) setting is improper
under V/F control, so the stall prevention
function is activated.
The base frequency does not match the motor
characteristics.
Regeneration avoidance operation is
performed
Load Stall prevention (torque limit) function is
activated due to a heavy load.
Parameter
setting
Motor
6.5.8 Speed varies during operation
Under Advanced magnetic flux vector control, the output frequency varies between 0 and 2 Hz as the load fluctuates. This is
a normal operation and not a fault.
Check
points
Load Load varies during an operation.
Input signal Frequency setting signal is varying.
The frequency setting signal is affected by
EMI.
Malfunction is occurring due to the undesirable
current generated when the transistor output
unit is connected.
Multi-speed command signal is chattering.
Parameter Fluctuation of power supply voltage is too
setting large.
Pr.80 Motor capacity and Pr.81 Number of
motor poles are not appropriate for the motor
capacity under Advanced magnetic flux vector
control, or PM motor control.
Wiring length exceeds 30 m when Advanced
magnetic flux vector control, or PM motor
control is selected.
Under V/F control, wiring is too long and a
voltage drop occurs.
Hunting occurs by the generated vibration, for
example, when structural rigidity at load side is
insufficient.
590
6. PROTECTIVE FUNCTIONS
6.5 Check first when you have a trouble
Possible cause
Possible cause
Countermeasure
Increase the acceleration/deceleration time.
Increase/decrease the Pr.0 Torque boost setting value by
0.5% increments so that stall prevention does not occur.
Under V/F control, set Pr.3 Base frequency, Pr.47 Second V/
F (base frequency).
Under Advanced magnetic flux vector control or PM motor
control, set Pr.84 Rated motor frequency.
If the frequency becomes unstable during regeneration
avoidance operation, decrease the setting of Pr.886
Regeneration avoidance voltage gain.
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.
Countermeasure
Select Advanced magnetic flux vector control.
Check the frequency setting signal.
Set filter to the analog input terminal using Pr.74 Input filter
time constant, Pr.822 Speed setting filter 1.
Take countermeasures against EMI, such as using shielded
wires for input signal lines.
Use terminal PC (terminal SD when source logic) as a common
terminal to prevent a malfunction caused by undesirable
current.
Take countermeasures to suppress chattering.
Under V/F control, change the Pr.19 Base frequency voltage
setting (approximately by 3%).
Check the settings of Pr.80 and Pr.81.
Perform offline auto tuning.
In the low-speed range, set 0.5% in Pr.0 Torque boost.
Change the control method to Advanced magnetic flux vector
control.
Disable automatic control functions, such as the energy saving
operation, fast-response current limit operation, regeneration
avoidance function, Advanced magnetic flux vector control, stall
prevention, and online auto tuning.
Under PID control, set smaller values to Pr.129 PID
proportional band and Pr.130 PID integral time.
Adjust so that the control gain decreases and the level of safety
increases.
Change Pr.72 PWM frequency selection setting.
Refer to
page
190
538
539
145
559
―
257
―
Refer to
page
145
―
326
73
55
―
539
145
353
538
145
―
179