Speed Varies During Operation - Mitsubishi Electric FR-E700 Instruction Manual

Troubleshooting
7.6.8

Speed varies during operation

Check points Possible Cause
Input signal
Load
Input signal
Parameter
Setting
Others
FR-E700 EC
Multi-speed command signal is chattering.
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.
Pr. 80 "Motor capacity" and Pr. 81
"Number of motor poles" setting is
improper for the capacities of the inverter
and the motor for Advanced magnetic flux
vector control or General-purpose mag-
netic flux vector control.
Fluctuation of power supply voltage is too
large.
Hunting occurs by the generated vibration,
for example, when structural rigidity at
load side is insufficient.
Wiring length exceeds 30m when
Advanced magnetic flux vector control or
General-purpose magnetic flux vector
control is performed.
Wiring length is too long for V/f control,
and a voltage drop occurs.
Check first when you have troubles
Countermeasures
Take countermeasures to suppress chat-
tering.
Select Advanced magnetic flux vector con-
trol or General-purpose magnetic flux vec-
tor 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.
Check the Pr. 80 "Motor capacity" and
Pr. 81 "Number of motor poles" setting.
Change the Pr. 19 "Base frequency volt-
age" setting (about 3%) under V/f control.
Disable automatic control functions, such
as energy saving operation, fast-response
current limit function, regeneration avoid-
ance function, Advanced magnetic flux
vector control, General-purpose magnetic
flux vector control, and stall prevention.
Adjust so that the control gain decreases
and the level of safety increases.
Change Pr. 72 "PWM frequency selection"
setting.
Perform offline auto tuning.
Adjust Pr. 0 Torque boost by increasing
with 0.5% increments for low-speed oper-
ation.
Change to Advanced magnetic flux vector
control or General-purpose magnetic flux
vector control.
Refer to
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