Once the permanent magnet brushless motor excitation-loss, basically can only choose to replace the motor, the maintenance cost is a lot of, and how to judge the permanent magnet motor magnetic loss, we look down.
1
the machine current normal at the beginning of the run, after a period of time, current, time is long, will be submitted to the inverter overload
vendors would first need to determine the air compressor frequency converter selection is correct, then confirm the inverter parameters have been altered.
if there is no problem, both may need to be done through the counter electromotive force, the nose and the motor off, no load identification, no-load running to the rated frequency, the output voltage is the counter electromotive force, if it is below the motor nameplate counter electromotive force more than 50 v, determined the motor demagnetization.
2
permanent magnet motor demagnetization after running current would exceed the rating more
those who only in low speed or high speed operation to overload or occasionally submitted to the overload situation generally not demagnetization.
3
永磁电机退磁是需要一定时间的，有的几个月甚至一两年
如果厂家选型错误导致报电流过载，不属于无刷电机退磁。
motor demagnetization for
the motor cooling fan is unusual, lead to motor temperature
the motor is not set temperature protection device
the environment temperature is too high,
the motor design is not reasonable
how to prevent permanent magnet motor demagnetization? ？ ？
correct selection of permanent magnet motor power
demagnetization and permanent magnet motor power to choose.
the correct choice of permanent magnet motor power can prevent or delay the demagnetization.
is the main reason of the permanent magnet synchronous motor demagnetization is temperature is too high, overload is the main reason for the high temperature.
so, when choosing the permanent magnet motor power should have a certain margin, according to the actual situation of the load, average about 20% more appropriate.
avoid overloading starting and frequent starting
cage asynchronous starting synchronous permanent magnet motor to avoid overloading starting or frequent starting directly.
asynchronous starting process, the starting torque is oscillation, the starting torque trough section, the stator magnetic field on the rotor magnetic pole is the demagnetization effect.
so try to avoid overloading and frequent starting asynchronous permanent magnet synchronous motor.
improvement design
the appropriate increase the thickness of the permanent magnet
from the perspective of the permanent magnet synchronous motor design and manufacturing, to consider the armature reaction, electromagnetic torque and the relations between and among permanent magnet demagnetization.
in the magnetic flux and torque winding current flux produced by the radial force windings are common in under the action of rotor surface is easy to cause permanent magnet demagnetization.
in the case of motor air gap is constant, to ensure that the permanent magnet demagnetization, not the most effective way is to appropriately increase the thickness of permanent magnet.
have ventilation inside the rotor slot loop, lowering the temperature rise of the rotor
important factors effecting the reliability of permanent magnet motor is a permanent magnet demagnetization.
the rotor temperature rise too high, permanent magnets will generate irreversible loss.
in the structural design, can design the rotor internal ventilation circuit, direct cooling magnetic steel. Not only reduces the magnet steel temperature, also can improve the efficiency.
