Speed Varies During Operation; Operation Mode Is Not Changed Properly - Mitsubishi Electric FR-F740 EC Instruction Manual

Check first when you have troubles
7.6.8

Speed varies during operation

Check points Possible cause
Load
Input signal
Parameter
Setting
7.6.9

Operation mode is not changed properly

Check points Possible cause
Input signal
Parameter
Setting
7 - 32
Load varies during an operation.
Frequency setting signal is varying.
The frequency setting signal is affected by
EMI.
Malfunction is occurring due to the unde-
sirable current generated when the tran-
sistor output unit is connected.
Multi-speed command signal is chattering.
Fluctuation of power supply voltage is too
large.
Pr. 80 "Motor capacity" setting is improper
for the capacities of the inverter and the
motor for Simple magnetic flux vector con-
trol.
Wiring length is too long for V/f control,
and a voltage drop occurs.
Hunting occurs by the generated vibration,
for example, when structural rigidity at
load side is insufficient.
Start signal (STF or STR) is ON.
Pr. 79 setting is improper.
Operation mode and a writing device do
not correspond.
Countermeasures
Select Simple magnetic flux vector control.
Check the frequency reference 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 undesira-
ble current.
Take countermeasures to suppress chat-
tering.
Change the Pr. 19 "Base frequency volt-
age" 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 avoid-
ance function, Simple magnetic flux vector
control, and stall prevention.
During the PID control, set smaller values
to Pr. 129 and Pr. 130.
Adjust so that the control gain decreases
and the level of safety increases.
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 the Pr. 79 "Operation mode selec-
tion" 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
the PU/EXT key on the operation panel
(press the PU key when the parameter
unit (FR-PU04/FR-PU07) is used) to
switch to the PU operation mode.
For other values (1 to 4, 6, 7), the opera-
tion mode is limited accordingly.
Check Pr. 79, Pr. 338, Pr. 339, Pr. 550 and
Pr. 551, and select an operation mode
suitable for the purpose.
Troubleshooting
Refer to
page
6-42
—
6-198
3-44
3-29
—
6-58
6-42
6-39
6-42
—
6-185
Refer to
page
6-229
6-229
6-229,
6-244