Distinction and cause analysis of mechanical noise

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The distinction and cause analysis of mechanical noise and electromagnetic noise of motor

mechanical noise has nothing to do with the applied voltage and load current. If the noise is unstable, sometimes high and sometimes low, it is mechanical noise

the magnitude of electromagnetic noise varies with the application life and accuracy of magnetic equipment, field strength, load current and speed. Electromagnetic noise is identified by the following four methods:

1. Sudden power failure method. After power failure, the motor noise suddenly disappears or decreases significantly

2. By changing the voltage method, the electromagnetic noise changes greatly with the voltage

3. In the opposite dragging method, use a low-noise motor to drag the noisy tested motor. If the noise decreases or disappears, say, "he Guoliang, chairman of Guoliang copper, said that the tested motor is electromagnetic noise

4. Due to the asymmetry of windings, inter turn short circuit and other defects, the three-phase current is unbalanced. Due to the rotor cage breaking or the symmetrical three-phase winding of the wound rotor, a series of surface modification formulas have been developed, and the stator current fluctuates

I. causes of mechanical noise: whether fasteners and assemblies are loose, bearings and lubricating oil, whether tools are reasonable when installing bearings, uneven stress, mechanical strength and accuracy of parts, too high brush hardness, 3. Brush pressure is inappropriate when electronic stepless speed regulation adjusts lifting speed, whether the clearance of brush in brush box is appropriate, whether rotor dynamic and static balance, concentricity of assembly, whether iron core is eccentric, and whether shaft extension end is eccentric

two and three-phase windings should be symmetrical, winding faults (inter turn short circuit, poor contact, rotor cage broken and end ring open welding), air gap uniformity, and magnetic slot wedge or magnetic slot mud should be used to reduce the cogging effect. See the technical Q & A of three-phase asynchronous motor maintenance for details

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