- 19 -
VI. Troubleshooting of Motor
If the daily checking and periodical checking in III. Maintenance/Checking are correctly done, the
motor satisfactorily works. Table 11 shows "Motor Troubleshooting" and Table 12 "Bearing
Troubles and Causes". They should be referred to for daily maintenance/checking.
Table 11 Motor Troubleshooting
Phenomena
Cause
Sh
af
t b
re
ak
ag
e
Lo
ud
n
oi
se
/la
rg
e v
ib
ra
tio
n
Over
heat
U
ne
ve
n
ro
ta
tio
n
Pr
ot
ec
tiv
e r
el
ay
op
er
at
io
n
Le
ak
ag
e
In
su
la
tio
n
re
sis
ta
nc
e l
ow
Remedy
M
ot
or
B
ea
rin
g
In
st
al
la
tio
n
Pl
ac
e
Ambient temperature is high
◎
○
◎
Ventilate well
Humidity is high
○
◎
Consult maker
Splashing of much water/oil
○
○
◎
Prevent splashing
Obstruction close to motor
◎
○
○
Secure necessary space
Large external vibration/impact
◎
○
Vibration proofing
Weak foundation
◎
Strengthen it
C
ou
pl
in
g
w
ith
lo
ad
D
ire
ct
co
up
lin
g
Misalignment
○
◎
○
Align correctly
Large unbalance of coupling
◎
Correct balance of coupling
B
el
t
Misalignment of center between
pulleys
◎
○
Align the center
Contact angle is small
◎
○
Make proper pulley diameter
Excessive tension of belt
◎
◎
Make proper belt tension
Load point too away from motor
◎
○
Put load point nearer the motor
Large pulley impedes cooling air of
motor
◎
○
Provide vent hole for pulley
O
th
er
s
Dust on rotating portion
◎
○
Remove dust
Large axial load
◎
Review axial
W
iri
ng
Large voltage drop
◎
○
◎
Investigate wiring diameter/length
Loosened terminals
◎
○
○
Retighten terminals
Incomplete earthing
○
◎
Complete earthing
Single-phase operation
◎
◎
◎
Investigate connecting circuit
Voltage unbalance
◎
○
○
Investigate control side
Wrong wiring of cooling fan
◎
○
Change connecting circuit
Wrong wiring of pulse oscillator
◎
Change connecting circuit (If trouble occurs
with pulse oscillator, replace it)
Lo
ad
Overload
○
◎
◎
Reduce load
Large number of starts
○
◎
○
Reduce number of starts
Large inertia of load
◎
○
Extend acceleration time
Large vibration of counterpart machine
◎
Investigate counterpart machine
Large unbalance of load
◎
○
Correct balance
O
th
er
s
Bearing abnormality (motor)
◎
◎
○
Repair at specialized factory
Disconnection of stator coil (motor)
○
○
◎
◎
◎
Repair at specialized factory
Abnormal bearing of cooling fan
○
◎
○
○
◎
Replace cooling fan
Disconnection of winding of cooling fan
◎
○
◎
Replace cooling fan
Abnormal bearing of pulse oscillator
◎
Replace pulse oscillator
Circuit failure of pulse oscillator
◎
Replace pulse oscillator
