Mitsubishi Electric 800 Series Instruction Manual page 590

6.5.4 Motor generates heat abnormally
Check Possible cause
points
Motor Motor fan is not working
(Dust is accumulated.)
Phase to phase insulation of the motor is
insufficient.
Main circuit The inverter output voltage (U, V, W) are
unbalanced.
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 circuit Phase sequence of output terminals U, V and
W is incorrect.
Input signal The start signals (forward rotation, reverse
rotation) are connected improperly.
The polarity of the frequency command is
negative during the polarity reversible
operation set by Pr.73 Analog input
selection.
6.5.6 Speed greatly differs from the setting
Check Possible cause
points
Input signal Frequency setting signal is incorrectly input.
The input signal lines are affected by external
EMI.
Parameter Pr.1 Maximum frequency, Pr.2 Minimum
setting frequency, Pr.18 High speed maximum
frequency, and Pr.902 to Pr.905 settings are
improper.
Pr.31 to Pr.36, Pr.552 (frequency jump)
settings are improper.
Load Stall prevention function is activated due to a
heavy load.
Parameter
setting
Motor
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.
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 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.
Refer to
―
―
607
351
591
Refer to
42
50,
318
Refer to
―
73
253
328
255
―
257
―
6. PROTECTIVE FUNCTIONS
6.5 Check first when you have a trouble
3
page
4
5
5
5
page
6
550
7
8
page 9
10
589