YASKAWA VS mini J7 Series Instruction Manual page 106

Trouble
The motor speed is
unstable. The motor
speed fluctuates when
operating with a light
load.
The Digital Operator
does not turn ON.
The LED of the Digital
Operator is unlit.
Cause
The stall prevention level dur-
ing running is too low.
Because the stall prevention level
during running (n57) is too low, the
output current reaches the set level
and the speed drops.
The load is too heavy.
If the load is too heavy, stall
prevention is activated, the output
frequency is stopped, and the
acceleration time is lengthened.
The carrier frequency is too
high.
If operating the motor with a light load,
a high carrier frequency may cause
the motor speed to fluctuate.
The V/f set value is too high for
a low speed operation.
Because the set value for the V/f is
too high, over-excitation occurs at low
speeds.
The maximum frequency and
base frequency were incorrect-
ly adjusted.
Example: To operate a 60 Hz motor at
40 Hz or less, the maximum
frequency and base frequency are set
to 40 Hz.
The Inverter is used for an op-
eration at 1.5 Hz or less.
The analog reference input is
unstable and has noise interfer-
ence.
The power is not being sup-
plied.
The breaker or other component on
the power input side is not turned ON,
and the power is not being supplied.
Short-circuit bar for terminals
+1 and +2 is not connected.
8. Fault Diagnosis
Corrective Actions
Check if the stall prevention level
during running (n57) is set to an
appropriate value.
Reduce the load.
Decrease the carrier frequency (n46).
Set the V/f (n09 to n15) according to
the load characteristics.
Set the maximum frequency and the
base frequency according to the
motor specifications.
Do not use the J7 Inverter for an
operation that runs at 1.5 Hz or less.
For an operation at 1.5 Hz or less,
use a different Inverter model.
Increase the set value for the filter
time constant.
Check if the power is being supplied.
Confirm that the short-circuit bar is
connected properly.
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