Speed Varies During Operation; Operation Mode Is Not Changed Properly - Mitsubishi Electric FR-F720P-0.75K to 110K Instruction Manual

5.5.8

Speed varies during operation

Check
points
Load Load varies during an operation. (V/F control)
Frequency setting signal is varying.
The frequency setting signal is affected by EMI.
Input
signal
Malfunction is occurring due to the undesirable current
generated when the transistor output unit is connected.
Multi-speed command signal is chattering.
Fluctuation of power supply voltage is too large.
The Pr.80 Motor capacity setting is inappropriate for the
inverter and motor capacities under Simple magnetic
flux vector control and IPM motor control.
Wiring length is too long for V/F control, and a voltage
drop occurs.
Parameter
Setting
Hunting occurs by the generated vibration, for example,
when structural rigidity at load side is insufficient.
5.5.9

Operation mode is not changed properly

Check
points
Input
Start signal (STF or STR) is ON.
signal
Pr. 79 setting is improper.
Parameter
Setting
Operation mode and a writing device do not
correspond.
Possible Cause
Possible Cause
Check first when you have a trouble
Countermeasures
Select Simple magnetic flux vector control
Check the frequency setting signal.
Set filter to the analog input terminal using Pr. 74 Input
filter time constant.
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.
Change the Pr. 19 Base frequency voltage setting (about
3%) under V/F control.
Check the Pr. 80 Motor capacity setting.
Adjust Pr. 0 Torque boost by increasing with 0.5%
increments for low-speed operation.
Change to Simple magnetic flux vector control.
Disable automatic control functions, such as energy
saving operation, fast-response current limit function,
regeneration avoidance function, Simple magnetic flux
vector control and stall prevention.
For PID control, set smaller values to Pr.129 PID
proportional band and Pr.130 PID integral time.
Lower the control gain, and adjust to increase the
stability.
Change Pr. 72 PWM frequency selection setting.
Countermeasures
Check that the STF and STR signals are OFF.
When either is ON, the operation mode cannot be
changed.
When Pr. 79 Operation mode selection setting is "0" (initial
value), the inverter is placed in the External operation
mode at input power ON. To switch to the PU operation
mode, press on the operation panel (press
when the parameter unit (FR-PU04/FR-PU07) is used) .
At other settings (1 to 4, 6, 7), the operation mode is
limited accordingly.
Check Pr. 79, Pr. 338, Pr. 339, Pr. 550, Pr. 551, and select
an operation mode suitable for the purpose.
Refer
to
page
89
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192
46
30
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98
89
87
89
—
182
Refer
to
page
206
206
206,
219
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