Motor Generates Heat Abnormally; Motor Rotates In The Opposite Direction; Speed Greatly Differs From The Setting - Mitsubishi Electric 800 Series Instruction Manual

6.5.4

Motor generates heat abnormally

Check
Possible cause
points
Motor fan is not working
(Dust is accumulated.)
Motor
Phase to phase insulation of the motor is
insufficient.
Main
The inverter output voltage (U, V, W) are
unbalanced.
circuit
Parameter
Pr.71 Applied motor setting is incorrect.
setting
―
Motor current is large.
6.5.5

Motor rotates in the opposite direction

Check
Possible cause
points
Main
Phase sequence of output terminals U, V and
W is incorrect.
circuit
The start signals (forward rotation, reverse
rotation) are connected improperly.
Input
The polarity of the frequency command is
signal
negative during the polarity reversible
operation set by Pr.73 Analog input
selection .
Input
signal
Torque command is negative during torque
Parameter control under vector control.
setting
6.5.6

Speed greatly differs from the setting

Check
Possible cause
points
Frequency setting signal is incorrectly input.
Input
The input signal lines are affected by external
signal
EMI.
Pr.1 Maximum frequency, Pr.2 Minimum
frequency, Pr.18 High speed maximum
Parameter
frequency, and Pr.902 to Pr.905 settings are
improper.
setting
Pr.31 to Pr.36, Pr.552 (frequency jump)
settings are improper.
Load
Parameter
Stall prevention (torque limit) function is
activated due to a heavy load.
setting
Motor
Check first when you have a trouble
Countermeasure
Clean the motor fan.
Improve the environment.
Check the insulation of the motor.
Check the output voltage of the inverter.
Check the insulation of the motor.
Check the Pr.71 Applied motor setting.
Refer to "6.5.11 Motor current is too large".
Countermeasure
Connect phase sequence of the output cables
(terminal U, V, W) to the motor correctly.
Check the wiring.
(STF: forward rotation, STR: reverse rotation)
Check the polarity of the frequency command.
Check the torque command value.
Countermeasure
Measure the input signal level.
Take countermeasures against EMI, such as using shielded
wires for input signal lines.
Check the settings of Pr.1, Pr.2, and Pr.18.
Check the Pr.902 to Pr.905 settings.
Narrow down the range of frequency jump.
Reduce the load weight.
Set Pr.22 Stall prevention operation level (torque limit level)
higher according to the load. (If Pr.22 is set too high, an
overcurrent trip (E.OC[]) is likely to occur.)
Check the capacities of the inverter and the motor.
PROTECTIVE FUNCTIONS
Refer to
page
―
―
666
423
653
Refer to
page
35
43, 421
393
190
Refer to
page
―
69
329
402
330
―
154, 332
―
6
651