Speed Varies During Operation; Operation Mode Is Not Changed Properly - Mitsubishi Electric 800 Series Instruction Manual

2.6.8

Speed varies during operation

Under Advanced magnetic flux vector control or Real sensorless 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
point
Load The load varies during an operation.
The frequency setting signal is varying.
The frequency setting signal is affected
by EMI.
Input
A malfunction is occurring due to the
signal
undesirable current generated when the
transistor output unit is connected.
An input signal is chattering.
Fluctuation of power supply voltage is too
large.
The Pr.80 Motor capacity and Pr.81
Number of motor poles settings are not
appropriate for the motor capacity under
Advanced magnetic flux vector control,
Real sensorless vector control, or PM
sensorless vector control.
The wiring length exceeds 30 m when
Advanced magnetic flux vector control,
Real sensorless vector control, or PM
Parameter
sensorless vector control is selected.
setting
Under V/F control, wiring is too long and
a voltage drop occurs.
Hunting occurs by the generated
vibration, for example, when structural
rigidity of the load is insufficient.
2.6.9

Operation mode is not changed properly

Check
point
Input
The start signal (STF or STR) is ON.
signal
The Pr.79 Operation mode selection
setting is not appropriate.
Parameter
setting
Operation mode and a writing device do
not correspond.
38
2. Protective Functions
2.6 Check first when you have a trouble
Possible cause
Possible cause
Select Advanced magnetic flux vector control or Real sensorless 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.
Use relay contacts with high contact reliability. When the chattering is caused by
noises, take measures against noises. Design a ladder program to prevent
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, adjust the Pr.0 Torque boost setting by 0.5% increments.
Change the control method to Advanced magnetic flux vector control or Real
sensorless vector control.
Disable automatic control functions, such as the energy saving operation, fast-
response current limit operation, torque limit, regeneration avoidance function,
Advanced magnetic flux vector control, Real sensorless vector control, droop
control, stall prevention, and online auto tuning.
For PID control, set smaller values to Pr.129 PID proportional band and Pr.130
PID integral time.
Lower the control gain to increase the stability.
Change the Pr.72 PWM frequency selection setting.
Check that the STF and STR signals are OFF.
When either is ON, the operation mode cannot be changed.
When the Pr.79 is set to "0 (initial value)", the operation mode is the External
operation mode at power ON. To switch to the PU operation mode, press the PU/
EXT key on the operation panel. At other settings (1 to 4, 6, 7), the operation mode
is limited accordingly.
Check Pr.79 Operation mode selection, Pr.338 Communication operation
command source, Pr.339 Communication speed command source, Pr.550
NET mode operation command source selection and Pr.551 PU mode
operation command source selection, and select an operation mode suitable for
the purpose.
Countermeasure
Countermeasure