Speed Varies During Operation - Mitsubishi Electric FR-A820-00046 Instruction Manual

Check first when you have a trouble
6.6.8

Speed varies during operation

Under Advanced magnetic flux vector control, Real sensorless vector control, vector control, and en-
coder feedback control, the output frequency varies between 0 and 2 Hz as the load fluctuates. This
is a normal operation and not a fault.
Check
points
Load
Input
signal
Parameter
setting
6 - 46
Possible cause
Load varies during an operation.
Frequency setting signal is varying.
The frequency setting signal is affected by
EMI.
Malfunction is occurring due to the
undesirable current generated when the
transistor output unit is connected.
Multi-speed command signal is chattering.
Feedback signal from the encoder is
affected by EMI.
Fluctuation of power supply voltage is too
large.
Pr. 80 "Motor capacity" and Pr. 81 "Number
of motor poles" are not appropriate for the
motor capacity under Advanced magnetic
flux vector control, Real sensorless vector
control, vector control, or PM sensorless
vector control.
Wiring length exceeds 30 m when
Advanced magnetic flux vector control, Real
sensorless vector control, vector control, or
PM sensorless vector control is selected.
Under V/F control, wiring is too long and a
voltage drop occurs.
Hunting occurs by the generated vibration,
for example, when structural rigidity at load
side is insufficient.
Countermeasure
Select Advanced magnetic flux vector control,
Real sensorless vector control, vector control, or
encoder feedback 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.
Place the encoder cable far from the EMI source
such as main circuit and power supply voltage.
Earth (ground) the shield of the encoder cable
to the enclosure using a metal P-clip or U-clip.
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, set 0.5% in Pr. 0 "Torque
boost".
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,
vector control, encoder feedback control, droop
control, stall prevention, online auto tuning,
notch filter, and orientation control.
Under 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.
Protective functions
Refer to
page
5-61, 5-730
⎯
5-416
3-1
2-50
⎯
2-77
5-690
5-61
5-72
5-688
5-61
⎯
5-227