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5-6 Troubleshooting MN894
Table 5-3 Troubleshooting Chart
Symptom Cause Corrective Action
Motor is not connected. Connect motor to T1, T2 and T3 of control.
MCP trips as it is
ST contact on control is always closed. Repair or replace logic control module.
MCP trips as it is
closed (also see
Improper input voltage. Obtain the correct source voltage at L1, L2 and L3.
c osed (a so see
Shunt Trip light
ON)
Shorted SCR. Replace SCR or power cell.
pg
comes ON)
Control transformer (if equipped) set for wrong
voltage.
Change tap connections for correct voltage.
MCP t i th
MCP trip setting is too low. Increase MCP Trip setting.
MCP trips as the
motor is started
Line voltage decreases during motor starting. Fix incoming power problem.
motor is started
(also see Shunt
Motor or wiring is defective. Check terminal and motor wiring.
(
a
l
so
see
Sh
un
t
Trip light comes
Capacitors on output of control. Remove capacitors or move to line side of control.
Trip light comes
O
N
)
Logic control module is defective. Replace logic control module.
ON)
Improper current calibration. Verify S1 settings for motor nameplate FLA rating.
MCP trips after
th t i
PF set too high. Reduce PF adjustment (rotate CCW).
p
the motor is
running (also see
Occasional line imbalance. Set S2-6 =ON to disable shunt trip while running.
runn
i
ng
(
a
l
so
see
Shunt Tri
p
li
g
ht
Ground or motor fault. Check motor wiring.
Shunt Trip light
comes ON)
S2-6=ON but no bypass contactor is installed. Check setting of S2-6. Should be Off.
Starter does
No line voltage. Restore line voltage.
Starter does
nothing when
Overload is open. Reset overload.
no
thi
ng
w
h
en
start button is
No contact closure across terminals 12 and 13. Check start circuit.
start button is
pressed.
Current trip occurs. Check S1 settings for correct current calibration.
pressed
.
Control module has no power. Check control transformer jumper.
Control does not
accelerate motor
CL set too low. Increase CL adjustment (rotate CW).
acce
l
era
t
e
mo
t
or
to full speed
(Stalls)
Line voltage decreases to less than minimum
operating voltage during motor starting.
Fix incoming power regulation problem.
Insufficient torque
available from
Improper current feedback. Verify S1 settings for motor nameplate FLA rating.
ava
il
a
bl
e
f
rom
current limit CL.
CL set too low. Increase CL adjustment (rotate CW).
Motor
accelerates too
Ramp up (RU) time set too long. Decrease RU (rotate CCW).
acce
l
era
t
es
t
oo
slowly.
Improper current feedback. Verify S1 settings for motor nameplate FLA rating.
Current limit (CL) set too high. Reduce CL (rotate CCW).
Ramp up time (RU) set too short. Increase RU (rotate CW).
Motor
Initial pulse time (PT) set too long. Reduce PT (rotate CCW).
M
o
t
or
accelerates too
Improper current feedback. Verify S1 settings for motor nameplate FLA rating.
accelerates too
quickly.
Light or no load (is dependent on motor load).
A lightly loaded motor will reach full speed with
low starting current or voltage. Motor may
require the use of a tachometer.
Decrease TU, increase RU or install tachometer.
Motor current
and voltage
oscillates after
start
Power factor correction set too high. Reduce PF setting (rotate CCW) until oscillation
stops.
Line voltage decreases to less than minimum
operating voltage during motor starting.
Fix incoming power regulation problem.
Motor is noisy or
Single phasing due to an open phase. Check wiring and overload heaters.
M
otor
i
s
no
i
sy
or
vibrates when
starting
Single phasing or unbalanced current due to a
non-firing SCR.
Check for shorted SCR and replace.
starting
Single phasing or unbalanced current due to a
defective logic control module.
Repair or replace the logic control module.
Defective motor. Check motor for shorts, opens or grounds.