Mitsubishi FREQROL-SF Troubleshooting Manual page 38

(14) Alarm No.31(0S) Overspeed
(The real speed of the motor is checked
and when it exceeds 115% of the motor
maximum
speed, this alarm occurs.)
Item Cause
The reference speed
exceeds 115% of the
maximum speed.
1
The speed control system o Observe and check the signal
is unstable and an over-
shoot occurs.
The motor built-in en-
coder is defective.
3
The printed circuit
board SF-CA card is
4
defective.
Check
with the following maximum
speed being set.
Parameter being set from
the amplifier:
Parameter being set from
the NC:
(See References l-2.2(2)
and 1.2.3(3).)
between the speed signal
terminals SMO and OM using
an oscilloscope (See Appen-
dixes l-4 and l-5).
saturated when it exceeds
10 V because too high speed
a
is set, check that the volt-
age rises to around 115% in
the speed mode of the status
display (see Section 1.1.1)
or using the NC CRT monitor.
alarm No_23(OSE), check the
encoder output signal wave-
form using the oscilloscope.
reference speed which is
slower than middle speed
the
and check that the frequen-
cies of the signals of the
A or B satisfy the
phase
following relation.
speed(rpm)
a new one and check that it
correctly
works.
1 Troubleshooting
1.3 Checking method and
remedy of trouble
Remedy
speed.
for motor maximum speed.
values of the speed loop
gain VKP and VKI (amplifier
parameter Y36 and #37 or NC
parameters #22 and X23).
(Note) To check the occurrence
(b) If the alarm does not
occur,
decrease the parameter
values of VKP and VKI.
alarm No.23(OSE), adjust or
replace the motor built-in
encoder with a new one.
board with a new one.
Section 2.4.4.)
(See
B