On-site and maintenance of the motor, the sound of the machine running is generally used to judge the cause of the machine failure or abnormality, and even prevent and deal with it in advance to avoid more serious failures. What they rely on is not the sixth sense, but the sound. With their experience and understanding of the machine, the on-site engineer can accurately analyze the abnormal condition of the machine. There are actually many different combined sounds in the machine, such as the wind shearing sound produced by the cooling fan, the pressure sound of the hydraulic pump, and the friction sound on the conveyor belt, etc. Most of the power sources of these operating mechanisms come from motors or is the air pressure element.
It takes a long time of experience, habit and accumulation to hear the abnormal sound produced by that part from the many sounds, and even to judge what kind of problem it is. change. Once the savvy field engineer finds that the sound of the machine begins to change, he will start to check the operation of the machine. This habit can often kill major failures that are still in their infancy and ensure that the machine can work safely and stably.
The external noise generated by abnormal motor can be divided into two types, mechanical and electromagnetic noise . The most common causes of mechanical noise include bearing wear, friction or collision of running parts, bending of the shaft and loosening of screws, etc. The noise frequency generated by this mechanical structure is low, and some even cause the machine to vibrate, which is easier for engineers to inspect and maintain.
Electromagnetic noise is relatively high-frequency and sharp, which is unbearable, but if the noise frequency is really too high, the human ear cannot hear it. It needs to be detected by relevant instruments and equipment, and it is impossible to rely on personnel to detect abnormalities in advance. The common electromagnetic noise comes from the phase imbalance of the motor, which may be caused by the imbalance of each phase winding or the instability of the input power supply; the motor driver is another main cause of electromagnetic noise, and the components inside the driver are aging or lost, etc. , are prone to abnormal high-frequency electromagnetic sound.
Motor sound signal analysis is actually a mature technical field, but it is usually used in special cases, such as the main drive motor of nuclear submarines and the giant water pump used in deep mines, to monitor whether large power motors are working properly. . Most of the motor applications rely on the engineer’s ears to evaluate the operation of the machine; only after abnormal conditions are found, it is possible to use the sound spectrum analyzer to assist in detecting the motor condition.
Failure analysis
Common causes of motor failure include physical external force impact, mechanical overload operation and improper maintenance. If some external impact points are located in the fragile parts of the machine, such as cooling fans or plastic protective covers, the stressed objects will be directly damaged, which is the part that is easy to check. However, if the external force strikes in an inconspicuous place or when the operation is overloaded, the axis, bearing or locking screw may be affected, and only a slight amount of deformation occurs, but these may be in the form of abnormal sound. It is also time-consuming to check. These minor losses may become more and more serious. If they cannot be detected at the early stage and repaired or replaced, it may eventually lead to a major accident in which the machine or motor is directly scrapped.
There are some simple inspection techniques that can be used. The motor is the main power source of the machine. The shaft and transmission elements are combined with the machine components. Therefore, during the inspection, the motor can be separated and run for a test. It means that the faulty part is not on the motor. Reconnect the motor and adjust the alignment and position of the transmission elements, etc., the abnormal noise problem has been improved or disappeared, which means that the shaft center is misaligned or the connecting mechanism such as the belt is loose. If the sound still exists, you can turn off the motor to stop the power output after running. The machine should be in an inertial operation state for a period of time. If it reaches a static state in an instant, it means that the frictional resistance on the mechanism is too large. Eccentric problem.
In addition, if the motor power is turned off, the machine can maintain the original inertial behavior, but the abnormal sound disappears instantly, which means that the sound is related to electricity, which may belong to electromagnetic noise. If you can smell the smell of burning at the same time, you should check the power cord or carbon deposition and other factors. Or check the input current and resistance value of each phase to determine whether the internal coil is broken or burned, causing torque imbalance and fault noise.
Sometimes it may even be necessary to disassemble the motor in order to detect the cause of the abnormal noise. For example, observe whether the internal coil is too loose, which will cause the coil to move under force when the motor is running to generate electromagnetic sound; the deformation of the rotor axis will cause the noise of the rotor and the stator rubbing against each other during rotation. The noise generated by the driver is mostly high-frequency humming, and it is easy to sometimes be good or bad. The main reason is mostly the aging of the capacitor, which cannot effectively suppress the fluctuation of the power supply. .
in conclusion
Industrial-grade motors have a high safety factor in design and manufacture, and are not prone to failure, but they still need to be maintained and repaired to ensure usage. The regular maintenance of the motor mostly includes cleaning, lubrication, inspection of couplings, load comparison, motor operating temperature inspection, heat dissipation function detection, monitoring of vibration and input power, etc., so as to maintain and detect the use of the motor. Common maintenance behaviors such as screw re-tightening and consumables update, including input power cables, cooling fans, bearings, couplings and other spare parts.
The best way to extend the life of a machine and detect failures is to understand its sound characteristics and monitor it continuously. Although it is just a simple action, as long as engineers or personnel use more refreshments, this action can achieve the effect of expected fault detection of the machine.
Post time: Jul-14-2022