电机，在设备领域是无处不在 Motors are everywhere in the equipment field
这是一个不孤单的设备 This is a device that is not alone
靠谱的泵需要靠谱的电机 A reliable pump requires a reliable motor
电机的好坏直接影响着设备能否正常运行 The quality of the motor directly affects whether the equipment can operate normally.
电机类型、软启动方式，选型步骤，损坏原因方式处理方法，优劣电机区别…..这一个个问题都是电机幸福指数的重要反映。
Motor type, soft start method, selection steps, damage causes and methods to deal with, the difference between good and bad motors… Each of these issues is an important reflection of the motor happiness index.
下面就让我们一同看看 Let us take a look below
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336170.png)
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336171.png)
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336172.png)
Structurally speaking, the principle of a DC motor is relatively simple, but its structure is complex and inconvenient to maintain.
The principle of AC motor is complex but the structure is relatively simple, and it is easier to maintain than DC motor.
Including the speed regulating device that controls the speed, the price of DC is higher than that of AC. Of course, the structure and maintenance are also very different.
In terms of performance, DC motors have stable speed and precise speed control, which cannot be achieved by AC motors. Therefore, under the strict requirements of speed, DC motors have to be used to replace AC motors.
AC motor speed regulation is relatively complex, but it is widely used because chemical plants use AC power.
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336173.png)
Ordinary motors are designed according to constant frequency and constant voltage, and cannot fully adapt to the speed regulation requirements of the inverter, so they cannot be used as variable frequency motors.
The frequency converter can produce varying degrees of harmonic voltages and currents during operation, causing the motor to operate under non-sinusoidal voltages and currents. The high-order harmonics inside will cause an increase in the stator copper loss, rotor copper loss, iron loss and additional losses of the motor. .
The most significant one is the rotor copper loss. These losses will cause the motor to generate additional heat, reduce efficiency, and reduce o
utput power. The temperature rise of ordinary motors generally increases by 10%-20%.
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336174.png)
The carrier frequency of the frequency converter ranges from several kilohertz to more than ten kilohertz, which causes the motor stator winding to withstand a very high voltage rise rate, which is equivalent to applying a steep impact voltage to the motor, causing the motor’s inter-turn insulation to withstand serious damage. test.
When ordinary motors are powered by frequency converters, the vibration and noise caused by electromagnetic, mechanical, ventilation and other factors will become more complicated.
The harmonics contained in the variable frequency power supply interfere with the inherent spatial harmonics of the electromagnetic part of the motor, forming various electromagnetic excitation forces, thereby increasing the noise.
Since the motor has a wide operating frequency range and a large rotational speed variation range, it is difficult for the frequencies of various electromagnetic force waves to avoid the natural vibration frequencies of the various structural parts of the motor.
When the power supply frequency is low, the losses caused by higher harmonics in the power supply are greater; secondly, when the motor speed is reduced, the cooling air volume decreases in proportion to the cube of the speed, resulting in the motor heat being unable to dissipate and the temperature rising sharply. increase, it is difficult to achieve constant torque output. (We recommend you to follow the “Mechanical Engineer” official account to grasp practical knowledge and industry information as soon as possible)
Generally, the insulation level of variable frequency motors is Class F or higher. The insulation strength to ground and the insulation strength of the wire turns should be strengthened. In particular, the ability of the insulation to withstand impulse voltage should be considered.
The variable frequency motor must fully consider the rigidity of the motor components and the entire body, and try to increase its natural frequency to avoid resonance with each force wave.
Frequency conversion motors generally use forced ventilation cooling, that is, the main motor cooling fan is driven by an independent motor.
Bearing insulation measures should be adopted for variable frequency motors with a capacity exceeding 160KW. Mainly, it is easy to produce magnetic circuit asymmetry, and also produce shaft current. When the current generated by other high-frequency components acts together, the shaft current will greatly increase, resulting in bearing damage, so insulation measures are generally required. For constant power variable frequency motors, when the speed exceeds 3000/min, special high-temperature resistant grease should be used to compensate for the temperature increase of the bearings.
The variable frequency motor cooling fan is powered by an independent power supply to ensure continuous heat dissipation.
电机基础知识02 Motor Basics 02
Type of load being driven, rated power, rated voltage, rated speed, and other conditions.
For continuous-running production machinery with stable load and no special requirements for starting and braking, ordinary squirrel-cage asynchronous motors should be preferred, which are widely used in machinery, water pumps, fans, etc.
![【电气知识】史上最全面的电机知识解说，从电机分类到选型，妥妥的干货！[Electrical Knowledge] The most comprehensive explanation of motor knowledge in history, from motor classification to selection, all the essential information! ---](https://www.ippdd.com/wp-content/uploads/2024/01/336175.png)
Production machinery that starts and brakes frequently and requires large starting and braking torques, such as bridge cranes, mine hoists, air compressors, irreversible rolling mills, etc., should use wound asynchronous motors.
Synchronous motors should be used where there is no speed regulation requirement, a constant speed is required or the power factor needs to be improved, such as medium and large capacity water pumps, air compressors, hoists, mills, etc.
调速范围要求在1∶3以上，且需连续稳定平滑调速的生产机械，宜采用他励直流电动机或用变频调速的鼠笼式异步电动机或同步电机，例如大型精密机床、龙门刨床、轧钢机、提升机等。
The speed regulation range is required to be above 1:3, and production machinery that requires continuous, stable and smooth speed regulation should use separately excited DC motors or squirrel cage asynchronous motors or synchronous motors with variable frequency speed regulation, such as large precision machine tools, gantry planers, Rolling mill, elevator, etc.
要求起动转距大，机械特性软的生产机械，使用串励或复励直流电动机，例如电车、电机车、重型起重机等。
Production machinery that requires large starting torque and soft mechanical properties uses series or compound-excitation DC motors, such as trams, electric locomotives, heavy cranes, etc.
Generally speaking, the motor can be roughly determined by providing the type of driven load, rated power, rated voltage, and rated speed of the motor.
But these basic parameters are far from enough if load requirements are to be optimally met.
Frequency, working system, overload requirements, insulation level, protection level, moment of inertia, load resistance torque curve, installation method, ambient temperature, altitude, outdoor requirements, etc. (provided based on specific circumstances)
You can prevent and eliminate faults in time through four methods: looking, listening, smelling and touching.
Observe whether there are any abnormalities during the operation of the motor. The main symptoms are as follows.
2. When the motor is severely overloaded or running out of phase, the speed will slow down and there will be a heavier “buzzing” sound.
3. The motor maintenance network operates normally, but when it suddenly stops, you will see sparks coming from loose connections; fuses blowing or certain parts getting stuck.
4. If the motor vibrates violently, the transmission device may be stuck, the motor may be poorly fixed, or the foot bolts may be loose, etc.
5. If there are discoloration, burn marks, smoke marks, etc. at the contact points and connections inside the motor, it may indicate local overheating, poor contact at the conductor connection, or burnt windings.
When the motor is running normally, it should emit a uniform and light “buzzing” sound without any noise or special sound.
If there is too much noise, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction, etc., it may be a precursor to a fault or a fault phenomenon.
1. Regarding electromagnetic noise, if the motor makes a high, low and heavy sound, the reasons may be as follows:
(1) The air gap between the stator and the rotor is uneven. At this time, the sound is high and low, and the interval between high and low sounds remains unchanged. This is caused by bearing wear and the stator and rotor are not concentric. (We recommend you to follow the “Mechanical Engineer” official account to grasp practical knowledge and industry information as soon as possible)
(2) The three-phase current is unbalanced. This is caused by incorrect grounding, short circuit or poor contact in the three-phase winding. If the sound is dull, it means that the motor is seriously overloaded or running out of phase.
(3) The iron core is loose. During the operation of the motor, the iron core fixing bolts loosen due to vibration, causing the iron core silicon steel sheets to loosen, causing noise.
The monitoring method is: put one end of the screwdriver against the bearing installation part and the other end close to your ear, and you can hear the sound of the bearing running. If the bearing is operating normally, its sound will be a continuous and small “rustling” sound, without sudden high and low changes and metal friction sound.
(1) There is a “squeaking” sound when the bearing is running. This is the sound of metal friction. It is generally caused by the lack of oil in the bearing. The bearing should be disassembled and an appropriate amount of grease should be added.
(2) If there is a “chirping” sound, it is the sound made when the balls are rotating. It is usually caused by the grease drying up or lack of oil. You can add an appropriate amount of grease.
(3) If there is a “clicking” or “squeaking” sound, it is caused by the irregular movement of the balls in the bearing. This is caused by damage to the balls in the bearing or the motor has not been used for a long time and the grease has dried up.
3. If the transmission mechanism and the driven mechanism make continuous sound instead of high and low, the following situations can be dealt with.
(2) The periodic “dong-dong” sound is caused by the looseness between the coupling or the pulley and the shaft and the wear of the key or keyway.
Check to see if there is a burnt smell. If there is a special paint smell, it means that the internal temperature of the motor is too high; if there is a heavy burnt smell or burnt smell, it may be that the insulation layer repair network has been broken down or the winding has been burned.
If there is no smell, you need to use a megohmmeter to measure the insulation resistance between the winding and the casing to be lower than 0.5M, and then dry it. If the resistance is zero, it means it is damaged.
To ensure safety, use the back of your hand to touch the motor housing and parts around the bearing.
5. If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.
Regulations stipulate that the maximum temperature of rolling bearings shall not exceed 95°C, and the maximum temperature of sliding bearings shall not exceed 80°C. And the temperature rise does not exceed 55℃ (the temperature rise is the bearing temperature minus the ambient temperature during the test).
1. Open the module cover and replace the damaged fuse, charging resistor and other components in the module.
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