Speed Varies During Operation - Mitsubishi Electric FR-A800 Series Instruction Manual

6.6.8

Speed varies during operation

Under Advanced magnetic flux vector control, Real sensorless vector control, Vector control, and encoder 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
point
Load The load varies during an operation.
The frequency setting signal is varying.
The frequency setting signal is affected by
EMI.
A malfunction is occurring due to the
Input
undesirable current generated when the
signal
transistor output unit is connected.
A multi-speed command signal is
chattering.
The feedback signal from the encoder is
affected by EMI.
Fluctuation of power supply voltage is too
large.
The Pr.80 Motor capacity and Pr.81
Number of motor poles settings are not
appropriate for the motor capacity under
Advanced magnetic flux vector control,
Real sensorless vector control, Vector
control, or PM sensorless vector control.
The wiring length exceeds 30 m when
Advanced magnetic flux vector control,
Real sensorless vector control, Vector
control, or PM sensorless vector control is
selected.
Parameter
setting
Under V/F control, wiring is too long and a
voltage drop occurs.
Hunting occurs by the generated vibration,
for example, when structural rigidity of the
load is insufficient.
806
6. PROTECTIVE FUNCTIONS
6.6 Check first when you have a trouble
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Possible cause
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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.
Run the encoder cable away from any EMI source such as the 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, adjust the Pr.0 Torque boost setting by
0.5% increments.
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.
For PID control, set smaller values to Pr.129 PID proportional
band and Pr.130 PID integral time.
Lower the control gain to increase the stability.
Change the Pr.72 PWM frequency selection setting.
Refer to
page
221, 736
—
503
118
74
—
91
707
221
532
706
221
—
356