Fuji Electric FRENIC-Ace series, User Manual

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6.5 When Codes Other Than Alarm Codes and Light Alarm Indication (
l-al
) are Displayed
6-28
[ 4 ] Speed fluctuation or current oscillation (e.g., hunting) occurs during running at
constant speed
Possible Causes Check and Measures
(1) Analog speed setting is
fluctuating.
Check the signals for the frequency command with Menu “I/O Checking”
using the keypad. (See Chapter 3 “3.4.4 Checking I/O signal status.”)

Increase the filter constants (C33, C38, and C43) for the frequency
command.
(2) An external frequency
command potentiometer is used
for frequency setting.
Check that there is no noise in the control signal wires from external
sources.

Separate the signal wires from the main power wires as far as
possible.

Use shielded or twisted wires for control signals.
Check whether the external frequency command potentiometer is
malfunctioning due to noise from the inverter.

Connect a capacitor to the output terminal of the potentiometer or
insert a ferrite core on the signal wire. See Chapter 2 “Fig. 2.2-9
Example of Noise Countermeasures”.
(3) Frequency switching or
multi-frequency command was
enabled.
Check whether the relay signal for switching the frequency command is
chattering.

If the relay contact is defective, replace the relay.
(4) The wiring length between the
inverter and the motor is too
long.
Check whether auto-torque boost, auto-energy saving operation, or
dynamic torque vector control is enabled.

Perform auto-tuning of the inverter for every motor to be used.

Disable the automatic control systems by setting F37* to “1”
(Constant torque load) and F42* to “0” (V/f control), then check that
the motor vibration stops.

Make the output wires as short as possible.
(5) The machinery is hunting due to
vibration caused by low rigidity
of the load. Or the current is
irregularly oscillating due to
special motor parameters.
After disabling all the automatic control systems such as auto torque
boost, auto energy saving operation, overload prevention control,
current limiter, torque limiter, anti-regenerative control, auto search for
idling motor speed, slip compensation, dynamic torque vector control,
droop control, overload stop function, speed control, online tuning, notch
filter, and observer, check that the motor vibration disappears.

Disable the functions causing the vibration.

Readjust the output current fluctuation damping gain (H80*).
Check that the motor vibration is suppressed if you decrease the value
of F26 (Motor sound (Carrier frequency)) or set F27 (Motor sound
(Tone)) to “0.”

Decrease the carrier frequency (F26) or set the tone to “0” (F27 =
0).