Speed Varies During Operation - Mitsubishi Electric FR-A720-0.4K Instruction Manual

5.5.8

Speed varies during operation

When Advanced magnetic flux vector control, Real sensorless vector control, vector control or encoder feedback control is
exercised, the output frequency varies with load fluctuation between 0 and 2Hz. This is a normal operation and is not a fault.
Check
points
Load Load varies during an operation.
Frequency setting signal is varying.
The frequency setting signal is affected by EMI.
Input
Malfunction is occurring due to the undesirable current
signal 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, or vector control.
Wiring length exceeds 30m when Advanced magnetic
flux vector control, Real sensorless vector control, or
vector control is selected.
Wiring length is too long for V/F control, and the a
voltage drop occurs.
Parameter
Setting
Hunting occurs by the generated vibration, for example,
when structural rigidity at load side is insufficient.
Possible Cause
Check first when you have a trouble
Countermeasures
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.
Change the Pr. 19 Base frequency voltage setting (about
3%) under V/F control.
Check the settings of Pr.80 Motor capacity and Pr.81
Number of motor poles.
Perform offline auto tuning.
Adjust the Pr. 0 Torque boost setting by increasing with
0.5% increments for the low-speed operation.
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, the fast-response current limit function,
the torque limit, the regeneration avoidance function,
Advanced magnetic flux vector control, Real sensorless
vector control, vector control, encoder feedback control,
droop control, the stall prevention, online auto tuning, the
notch filter, and orientation control.
During the 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.
Refer
to
page
92, 381
—
292
54
29
—
36
159
92
189
146
92
—
284
5
423