The normal operation of the motor should be issued a uniform and lighter "buzzing" sound, no noise, and special sound. Too much noise, electromagnetic noise, bearing noise, ventilation noise, mechanical friction sound, may be a sign of failure or malfunction phenomenon.

     Electromagnetic noise, electric motors fluctuated heavy sound, the cause may be the following.

    (1) non-uniform air gap between the stator and the rotor, the sound peaks and valleys and the high and low interval is the same, this is so that the stator and rotor bearing wear due to heart.

    (2) three-phase current imbalance. This is a three-phase winding mistaken ground, short circuit or poor contact and other reasons, if the sound is very dull serious motor overload or missing running.

    (3) the loose core. Motor is running due to vibration caused by loose mounting bolts leaving the core the loose core silicon steel, making noises.

     bearing noise, the motor is running frequently monitored. Listening: the end of the screwdriver to withstand the bearing mounting parts and the other end to your ear, you can hear the sound of bearing operation. If the bearing is operating normally, the sound is continuous small "imperfections" sound, there will be peaks and valleys in the low transition metal friction sound. The following sound compared irregularities.

     (1) bearing operation "creak" sound, this is the sound of metal friction is generally caused by bearings in oil, open the bearing filling amount of grease.

     (2) If there is "ji Mile" sound, the sound of the ball rotates, generally dry grease or lack of oil caused by filling the right amount of grease.

     (3) "Titicaca" sound or "crunch" sound, interest bearing ball irregular movement and sound, this is due to the bearing ball damage or motor is not being used for a long period of grease dried up.

     Issued by the drive mechanism and the drive mechanism is continuous rather than suddenly valleys low sound processing can be divided into the following situations.

     (1) periodic "flap" sound, belt connector is not smooth.

     (2) periodic "pound" sound between the shaft coupling or pulley loose and key or keyway wear caused.

     (3) uneven sound of the collision, causing for blades collisions fan cover.