Mitsubishi Electric FR-D720S SC EC, Instruction Manual

Page: 462 / 512

Check first when you have troubles Troubleshooting
7 - 26
7.6.8 Speed varies during operation
When the slip compensation is selected, the output frequency varies between 0 and 2Hz as with
load fluctuates. This is a normal operation and not a fault.
Check points Possible Cause Countermeasures
Refer to
Page
Input signal Multi-speed command signal is chattering.
Take countermeasures to suppress chat-
tering.
—
Load Load varies during an operation.
Select General-purpose magnetic flux
vector control.
6-29
Input signal
Frequency setting signal is varying. Check the frequency reference signal. —
The frequency setting signal is affected by
EMI.
Set filter to the analog input terminal using
Pr. 74 "Input filter time constant".
6-152
Take countermeasures against EMI, such
as using shielded wires for input signal
lines.
3-44
Malfunction is occurring due to the unde-
sirable current generated when the tran-
sistor output unit is connected.
Use terminal PC (terminal SD when
source logic) as a common terminal to
prevent a malfunction caused by undesira-
ble current.
3-29
Parameter
Setting
Pr. 80 "Motor capacity" setting is improper
for the capacities of the inverter and the
motor for General-purpose magnetic flux
vector control.
Check the Pr. 80 "Motor capacity"setting. 6-29
Fluctuation of power supply voltage is too
large. Change the Pr. 19 "Base frequency volt-
age" setting (about 3%) under V/f control.
6-44
Hunting occurs by the generated vibration,
for example, when structural rigidity at
load side is insufficient.
Disable automatic control functions, such
as energy saving operation, fast-response
current limit function, regeneration avoid-
ance function, General-purpose magnetic
flux vector control, and stall prevention.
During the 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.
6-144
Others
Wiring length exceeds 30m when General-
purpose magnetic flux vector control is
performed.
Perform offline auto tuning. 6-74
Wiring length is too long for V/f control,
and a voltage drop occurs.
Adjust Pr. 0 Torque boost by increasing
with 0.5% increments for low-speed
operation.
6-26
Change to General-purpose magnetic flux
vector control.
6-29