Q&A of Motor Maintenance Technology ★ What is a winding?
Answer: Armature winding is the core part of DC motor, and it is a coil wound by copper enameled wire. When the armature winding rotates in the magnetic field of the motor, it will produce electromotive force.
★ What is a magnetic field?
Answer: The force field around a permanent magnet or current and the space or magnetic range that all magnetic forces can reach.
★ What is the magnetic field strength?
Answer: The magnetic field intensity of an infinite conductor flowing at a distance of1/2m is defined as 1A/m (ampere/meter, Si); In the CGS system of units (cm-g-s), in order to commemorate Oster's contribution to electromagnetism, the magnetic field intensity of an infinite wire carrying current 1 amp at a distance of 0.2 cm from the wire is defined as 10e (Oster),10e =1/4./kloc.
★ What is Ampere's Law?
Answer: Hold the wire with your right hand, so that the direction of the straight thumb is consistent with the direction of the current, then the direction pointed by the bent four fingers is the winding direction of the magnetic induction line.
★ What is magnetic flux?
A: Magnetic flux is also called magnetic flux: there is a plane perpendicular to the direction of the magnetic field in a uniform magnetic field. The magnetic induction intensity of the magnetic field is B, and the area of the plane is S. We define the product of the magnetic induction intensity B and the area S, which is called the magnetic flux passing through this plane.
★ What is a stator?
Answer: A part of the brush or brushless motor does not turn when working. The motor shaft of hub brushless or toothless motor is called stator, and this kind of motor can be called internal stator motor.
★ What is a rotor?
Answer: The rotating part of the brush or brushless motor when it works. The shell of hub brushless or toothless motor is called rotor, and this kind of motor can be called outer rotor motor.
★ What is a carbon brush?
Answer: The inside of the brush motor is against the surface of the inverter. When the motor rotates, it transmits electric energy to the coil through the inverter. Because its main component is carbon, it is called carbon brush, which is easy to wear. Maintenance and replacement should be carried out regularly, and carbon deposits should be removed.
★ What is a brush grip?
Answer: Mechanical guide groove is used to fix and maintain the position of carbon brush in the brush motor.
★ What is an inverter?
Answer: There are mutually insulated strip metal surfaces in the brush motor. When the motor rotor rotates, the strip metal alternately contacts the positive and negative poles of the brush, thus realizing the alternating change of the current direction of the motor coil and completing the commutation of the brush motor coil.
★ What is phase sequence?
Answer: The arrangement order of brushless motor coils.
★ What is magnetic steel?
Answer: It is generally used to refer to magnetic materials with high magnetic field strength. The motors of electric vehicles are all made of NdFeB _ rare earth magnetic steel.
★ What is electromotive force?
Answer: It is produced by cutting the magnetic field lines by the motor rotor, which is opposite to the direction of the external power supply, so it is called back electromotive force.
★ What is a brush motor?
Answer: When the motor is working, the coil and commutator rotate, but the magnetic steel and carbon brush do not rotate. The alternating change of coil current direction is realized by the commutator and brush rotating with the motor. In the electric vehicle industry, brush motors are divided into high-speed brush motors and low-speed brush motors. There are many differences between brush motor and brushless motor. As can be seen from the text, the brush motor has a carbon brush and the brushless motor has no carbon brush.
★ What is a low-speed brush motor? What are the characteristics?
A: In the electric vehicle industry, the low-speed brush motor refers to a hub-type low-speed high-torque gearless brush DC motor, and the relative speed of the motor stator and rotor is the speed of the wheel. There are 5~7 pairs of magnetic steel on the stator and 39~57 slots on the armature of the rotor. Because the armature winding is fixed in the wheel cover, with the help of the rotating shell, heat is easily dissipated. The rotating shell is woven by 36 spokes, which is more conducive to heat conduction. Technical training micro signal deserves your attention!
★ What are the characteristics of motors with brushes and teeth?
Answer: What are the main hidden dangers of brush motors? Brush wear? Users should note that there are two kinds of brush motors: toothed and toothless. At present, many manufacturers choose the tooth brush motor, not the high-speed motor. Toothed? That is, the speed of the motor is reduced by the gear reduction mechanism (because the national standard stipulates that the speed of electric vehicles cannot exceed 20 kilometers per hour, the speed of the motor should be around 170 rpm). Because the high-speed motor slows down through gears, it is characterized by strong rider's power and strong climbing ability when starting. The electric wheel hub is closed, and only lubricating oil is added before leaving the factory, so it is difficult for users to carry out daily maintenance. And the gear itself has mechanical wear. For about a year, due to insufficient lubrication, the gear wear is aggravated, the noise is increased, and the current is also increased during use, which affects the life of the motor and battery.
★ What is a brushless motor?
Because the controller provides direct current with different current directions, the alternating current direction of the coil in the motor can be realized. There is no brush and commutator between the rotor and stator of brushless motor.
★ How to realize motor commutation?
Answer: When a brushless or brushed motor rotates, it is necessary to alternately change the direction of energization of the internal coil of the motor so that the motor rotates continuously. Commutation of brush motor is completed by inverter and brush, and brushless motor is completed by controller.
★ What is lack of phase?
Answer: One of the three-phase circuits of the brushless motor or the brushless controller can't work. The missing phase is divided into main phase missing phase and Hall missing phase. Explain that the motor is shaking, unable to work, or weak in rotation and loud in noise. The controller works in the state of lack of phase and is easy to burn out.
★ What are the common motor types?
Answer: The common motors are: brushed and toothed hub motor, brushed and toothless hub motor, brushless and toothless hub motor, side hanging motor, etc.
★ How to distinguish high and low speed motors from motor types?
A:
Brushless hub motors and brushless hub motors belong to high-speed motors;
B Both brushless and toothless hub motors are low-speed motors.
★ What is the definition of motor power?
Answer: The power of the motor refers to the ratio of the mechanical energy output by the motor to the electric energy provided by the power supply.
★ Why choose the power of the motor? What is the significance of choosing motor power?
Answer: The selection of rated power of motor is a very important and complicated issue. When loaded, if the rated power of the motor is too large, the motor will often run under light load, and the capacity of the motor itself will not be fully exerted, which will become? Big horse-drawn car? At the same time, the low efficiency and poor performance of the motor will increase the operating cost. On the contrary, the rated power of the motor is required to be small, that is? Small horse-drawn cart? If the motor current exceeds the rated current, the internal loss of the motor will increase, and the low efficiency will be negligible. It is important to affect the life of the motor. Even if the overload is not much, the life of the motor will be reduced even more. Excessive overload will damage the insulation performance of motor insulation materials, and even burn out. Of course, the rated power of the motor is small, and it may not be able to drag the load at all, which will cause the motor to be overheated and damaged for a long time. Therefore, the rated power of the motor should be strictly selected according to the operation of the electric vehicle.
★ Why do ordinary DC brushless motors have three halls?
A: In short, in order to rotate the DC brushless motor, there must always be a certain angle between the magnetic field of the stator coil and the magnetic field of the rotor permanent magnet. The process of rotor rotation is also the process of changing the direction of rotor magnetic field. In order to make the magnetic field between them have an angle, the magnetic field direction of the stator coil must be changed to some extent. So how do you know the direction of changing the stator magnetic field? That depends on those three halls. It can be thought that those three Halls are responsible for telling the controller when to change the direction of the current.
★ What is the approximate range of Hall power consumption of brushless motor?
A: The power consumption of the brushless motor Hall varies from 6 Ma to 20 Ma.
★ At what temperature can a general motor work normally? What is the maximum temperature that the motor can withstand?
Answer: If the measured temperature of the motor cover exceeds the ambient temperature by more than 25 degrees, it means that the temperature rise of the motor has exceeded the normal range. Generally, the temperature rise of the motor should be below 20 degrees. Generally, the motor coil is wound with enameled wire. When the temperature of enameled wire is higher than 150℃, the paint film will fall off because of the high temperature, resulting in short circuit of the coil. When the coil temperature is above 150 degrees, the temperature of the motor shell is about 100 degrees, so the highest temperature that the motor can bear is 100 degrees according to its shell temperature.
★ The motor temperature should be below 20 degrees Celsius, that is, when the temperature of the motor end cover exceeds the ambient temperature, it should be less than 20 degrees Celsius, but what is the reason for the motor heating exceeding 20 degrees Celsius?
A: The direct cause of motor fever is the large current. Generally, it may be caused by short circuit or open circuit of coil, demagnetization of magnetic steel or low efficiency of motor. Under normal circumstances, the motor runs for a long time and has a large current.
★ What causes the motor to heat up? What kind of process is this?
Answer: When the motor is running with load, there is power loss in the motor, which will eventually become heat energy, which will increase the temperature of the motor and exceed the ambient temperature. The temperature of the motor is higher than the ambient temperature, which is called temperature rise. Once the temperature rises, the motor will radiate heat to the surroundings; The higher the temperature, the faster the heat dissipation. When the heat emitted by the motor per unit time is equal to the heat emitted, the temperature of the motor will not rise, but keep a stable temperature, that is, in a state of heat generation and heat dissipation balance.
★ What is the allowable temperature rise for general clicking? Which part of the motor is most affected by the temperature rise of the motor? How is it defined?
Answer: When the motor is running with load, the greater the load, the better the output power (regardless of mechanical strength). However, the greater the output power and loss power, the higher the temperature. As we know, the weakest heat resistance in motors is insulation materials, such as enameled wires. The temperature resistance of insulating materials is limited. Within this limit, the physical, chemical, mechanical and electrical properties of insulating materials are very stable, and its working life is generally about 20 years. Beyond this limit, the life of insulating materials will be shortened sharply, or even burned. This temperature limit is called the allowable temperature of insulating materials. The allowable temperature of insulation material is the allowable temperature of motor; The life of insulating material is generally the life of motor.
Motor maintenance skill 1: matters needing attention
1. All the circuits and electrical connections of electric motor are designed and guided by professionals, and users are not allowed to modify and connect them themselves, otherwise failures and accidents (including serious consequences such as fire and traffic accidents) will easily occur.
2. Although all kinds of electrical appliances and components of electric vehicles have certain waterproof function, the waterproof performance will be reduced due to damage and aging, so electric vehicles should not run on the road surface with water depth that can immerse the motor shaft. When parking or driving in the rain, cover all kinds of switches, knobs and other parts with a rain cover to prevent these electrical equipment from being damaged by moisture.
3. If the motor is found to have fever (above 90℃), smoke, peculiar smell, abnormal sound or other abnormal phenomena, it should be stopped immediately and sent to our distribution point for treatment. Do not disassemble the motor by yourself.
4, should avoid the vehicle in the case of overload, insufficient tire pressure or driving on a long and steep slope, otherwise the motor is in danger of burning.
5. The electric wheel hub shall not be violently impacted, and the electric vehicle shall not be forcibly started in a blocked state. When the electric vehicle can't be started due to obstacles, don't start it repeatedly, and start the motor after removing the obstacles of the electric vehicle.
6. For motors equipped with chains, remember to fill the chain with lubricating oil frequently, which can not only reduce the wear and tear of transmission parts, prolong their life, but also reduce the transmission noise.
Two: Maintenance rules
1. In the use of electric vehicles, users generally do not need to maintain the internal parts of the motor, but only need to check the state of the fasteners installed on the rear fork of the electric hub. If the nut is found to be loose, tighten the nut in time or ask a professional to check and handle it.
2. When the motor stops running, remove the dust and sludge outside the motor in time, keep the motor clean, prevent oil and water from entering the motor, and do not spray water directly when cleaning.
3. Check whether the lead-out wire of the motor is scratched and whether there is abnormal noise when the motor is running. If necessary, it should be sent to our company's distribution point for processing, and professionals should be invited to check and handle it.
4. If the motor is equipped with a chain, please lubricate the chain regularly.
Technical Points of Motor Maintenance 1 Technical Parameter Collection
Collect the technical parameters of the faulty motor, and judge the fault type of the motor according to the operating environment. Especially when the motor is stationary, the corresponding turns are increased to meet the power requirements and reduce the load. The operation mode of three-phase asynchronous motor is started by capacitor, and the number of winding turns is adjusted according to maintenance requirements. Increase or decrease the number of turns to stabilize the voltage, reduce the current and ensure that the total magnetic field remains unchanged. Check the capacity and withstand voltage when starting the capacitor, and increase the capacitor appropriately.
2 Maintenance operation skills
It needs to be clear that the main cause of motor failure is the actual maintenance operation. In general, motor maintenance will have corresponding reference materials to help carry out maintenance inspection. The spatial position in the stator slot of the motor needs to be fixed. The number of turns is actually measured in the original space system, and the motor slot allowance is appropriately adjusted according to the number of turns. Coating insulating paint on the motor slot can increase the gap to a certain extent and provide conditions for increasing the number of turns. The connection mode of capacitor operation will have different performances in carrying capacity, operating efficiency and starting torque. Capacitance operation will also increase the corresponding series components.
3 motor test
After the motor overhaul, many tests will be carried out, mainly insulation. Voltage, torque, etc. Comprehensive judgment to determine whether the motor can run normally. The step-down test of three-phase transformer can also judge the electronic condition of rotor-less. The variation of voltage parameters can be obtained by measuring the electromagnetic field. The test is mainly aimed at the repaired motor, which cannot pass 220V directly, and the rated current test is completed under the step-down state of the three-phase transformer. The operating environment of the motor should be consistent with the number of turns of the coil.
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