If the motor emits a low-frequency "buzzing" sound, the general reasons are as follows:

When the inner cover is installed, the motor shaft rubs the inner cover. At this time, the sound is continuous. When handling, the inner cover can be changed to tighten again.

After long-distance transportation of the motor, there will be obvious bearing noise during trial operation, which can be solved by adding grease, which is caused by the turbulence during transportation and the outflow of grease from the bearing part.

After running for a period of time, the bearing noise must be carefully listened to with a listening stick or screwdriver on the bearing cover. If the bearing running sound is uniform, add oil to solve it. If there is obvious "chuckle" sound in the bearing running, the bearing must be replaced and the cylindricity of the bearing chamber must be checked at the same time. Because the end cover of cast iron or steel plate will produce stress in the manufacturing process, after the motor runs for a period of time, with the release of stress, the bearing chamber will be deformed, and the cylindricity may be out of tolerance. The best way to check whether the bearing chamber is deformed is to reinstall the old bearing.

Possible causes:

(1) the power supply voltage is low;

(2) The original angle connection was misconnected to the star connection;

(3) The cage bar end of the squirrel cage rotor is desoldered, loose or broken.

Treatment methods:(1) Increase the voltage;(2) Check the nameplate wiring method and correct the stator winding wiring method;(3) After inspection and symptomatic treatment.

The rotating shaft is supported by the bearing and is the heaviest part of the load, and it is also a component that is easy to wear.

(1) Fault inspection

Inspection during operation: when the rolling bearing is short of oil, you will hear the sound of bone rolling. if you hear the discontinuous sound of stem, it may be the rupture of the bearing steel ring. When the bearing is mixed with sand and other debris or the bearing parts are slightly worn, a slight noise will be generated.

Inspection after disassembly: first check whether the rolling element of the bearing and the inner and outer steel rings are damaged, rusted and scarred, then pinch the inner ring of the bearing with one hand to balance the bearing, and push the outer steel ring with the other hand. If the bearing is in good condition, the outer steel ring should rotate smoothly without vibration and obvious jam during rotation, and the outer steel ring should not reverse after stopping, otherwise the bearing can no longer be used. The left hand grips the outer ring, the right hand grips the inner steel ring, and pushes hard in all directions. If it feels loose when pushing, it is severely worn.

(2) Fault Repair

The rust spots on the outer surface of the bearing can be erased with No. 00 sandpaper, and then cleaned in gasoline; or when the bearing is cracked, the inner and outer rings are broken or the bearing is excessively worn, the new bearing should be replaced. When replacing a new bearing, choose the same bearing as the original model.

If there are cracks in the casing and the end cover, surfacing welding shall be carried out for repair. If the bearing boring gap is too large, causing the bearing end cover to fit too loosely, the bearing hole wall can be evenly punched with a punch for stimulation, and then the bearing can be driven into the end cover. For motors with high power, the required size of the bearing can also be finally processed by means of inlaying or electroplating.

Possible causes:

(1) Wrong connection of stator winding, local short circuit or grounding, resulting in unbalanced three-phase current and causing noise;

(2) there are foreign bodies or serious shortage of lubricating oil inside the bearing.

Treatment methods:(1) Check separately and prescribe the right medicine;(2) After cleaning the bearing, replace the new lubricating oil with 1/2-1/3 of the bearing chamber.

Possible causes:

(1) The insulation of the motor lead wire or the insulated wire plate of the junction box;

(2) The winding end touches the casing;

(3) The motor housing is not reliably grounded

Treatment methods:(1) restore the insulation of the motor lead wire or replace the insulation plate of the junction box;(2) If the grounding phenomenon disappears after the end cover is removed, the end cover can be installed after the winding end is insulated;(3) According to the grounding requirements, the motor shell shall be reliably grounded.

Possible causes:

(1) The power supply voltage is too low, and the temperature rise of the motor is too high under the rated load;

(2) The motor is poorly ventilated or the ambient humidity is too high;

(3) motor overload or single-phase operation;

(4) the motor starts frequently or too many times of positive and negative rotation;

(5) the stator and rotor rub.

Treatment methods:(1) measuring no-load and load voltages;(2) check the motor fan and clean the ventilation duct, strengthen ventilation to reduce the ring temperature;(3) after checking the current of each phase with clamp ammeter, symptomatic treatment;(4) Reduce the number of positive and negative motor, or replace the motor suitable for frequent starting and positive and negative motor;(5) Treatment of syndrome after inspection.

Possible causes:

(1) the power supply voltage is low;

(2) The original angle connection was misconnected to the star connection;

(3) The cage bar end of the squirrel cage rotor is desoldered, loose or broken.

Treatment methods:(1) Increase the voltage;(2) Check the nameplate wiring method and correct the stator winding wiring method;(3) After inspection and symptomatic treatment.

After the (I) timing is turned on, the motor cannot be started, but there is a buzzing sound.

Possible causes:

(1) The power supply is not fully connected to single-phase start;

(2) Motor overload;

(3) Stuck by dragging machinery;

(4) The rotor circuit of the wound motor is opened and broken;

(5) The internal head end of the stator may be connected incorrectly, or there may be disconnection or short circuit.

Treatment methods:(1) check each pair of contacts of power cord, motor lead wire, fuse and switch, find out the open circuit position and eliminate it;(2) no-load or half-load starting after unloading;(3) Check the dragged machinery and eliminate the fault;(4) Check the joint condition of each contactor of brush, slip ring and starting resistor;(5) Re-judge the end and end of the three phases, and check whether the three-phase winding is shimmering and short circuit.