8-23
·The DC injection braking is insufficient.
If the DC braking poweris insufficient, adjust thevalue in n089 for DC injection con-
trol current.
·An inappropriate brake is being used.
Use a brake intended for braking rather than holding.
8-2-8 Motor Burns
·The load is too big.
If the load of the motor is too big and the motor is used with the effective torque
exceeding the rated torque of the motor, the motor will burn out. For example, the
rated torque of the motor and capacity may be limited to eight hours of use if the
inscription on the motor states that the motor is rated for eight hours. If the 8-hour
rated torque is used for normal operation, it may cause the motor to bun out.
Reducetheloadamountbyeitherreducingtheloadorlengtheningtheacceleration/
deceleration time. Also consider increasing the motor capacity.
·The ambient temperature is too high.
Theratingofthemotor is determined within aparticularambientoperatingtempera-
ture range. The motor will burn out if it runs continuously at the rated torque in an
environment in which the maximum ambient operating temperature is exceeded.
Lowertheambienttemperatureofthemotortowithintheacceptableambientoperat-
ing temperature range.
·The withstand voltage between the phases of the motor is insufficient.
When the motor is connectedto the output of theInverter, a surge will begenerated
between the switching of the Inverter and the coil of the motor.
Normally, the maximum surge voltage is approximately three times the input power
supply voltage of the Inverter (i.e., approximately 600 Vfor 200-V Inverters, 1,200 V
for 400-V Inverters).
Therefore, the dielectric strength of the motor to be used must be higher than the
maximum surge voltage.
In particular, use a dedicated motor for 400-V Inverters.
Maintenance Operations Chapter 8
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