One hundred thousand motor why?

Questions and answers about basic knowledge about motors

    ★What is a motor?

    Answer: The motor is a component that converts battery energy into mechanical energy and drives the wheels of electric vehicles to rotate.

    ★What is winding?

    Answer: The armature winding is the core part of the DC motor and is a coil wound with copper enameled wire. When the armature winding rotates in the magnetic field of the motor, an electromotive force is generated.

    ★What is a magnetic field?

    Answer: The force field generated around the permanent magnet or current and the space or range of magnetic force that can be reached by magnetic force.

    ★What is magnetic field strength?

    Answer: Define the magnetic field strength of an infinitely long wire carrying a current of 1 ampere at a distance of 1/2 meter from the wire to be 1A/m (ampere/meter, SI); in the CGS unit system (centimeter-gram-second) , in order to commemorate Oersted's contribution to electromagnetism, the magnetic field strength of an infinitely long wire carrying a current of 1 ampere at a distance of 0.2 cm from the wire is defined as 10e (Oersted), 10e=1/4.103/m, magnetic field Strength is usually represented by H.

    ★What is Ampere’s rule?

    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 four bent fingers is the direction of the magnetic field lines.

    ★What is magnetic flux?

    Answer: Magnetic flux is also called magnetic flux: Suppose 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 through The magnetic flux on this surface.

    ★What is a stator?

    Answer: The part of the brush or brushless motor that does not rotate when it is working. The motor shaft of a hub-type brushed or brushless toothless motor is called the stator, and this type of motor can be called an internal stator motor.

    ★What is a rotor?

    Answer: The part that a brush or brushless motor rotates when it is working. The casing of a hub-type brushed or brushless toothless motor is called a rotor, and this type of motor can be called an external rotor motor.

    ★What is a carbon brush?

    Answer: The inside of the brushed motor presses against the surface of the phase converter. When the motor rotates, electric energy is delivered to the coil through the phase converter. Since its main component is carbon, it is called a carbon brush, and it is easy to wear. It should be maintained and replaced regularly, and carbon deposits should be cleaned.

    ★What is a brush grip?

    Answer: The mechanical guide groove inside the brushed motor holds and maintains the position of the carbon brush.

    ★What is a phase converter?

    Answer: There are strip-shaped metal surfaces that are insulated from each other inside the brush motor. As the motor rotor rotates, the strip-shaped metal alternately contacts the positive and negative poles of the brush, realizing the alternating positive and negative changes in the current direction of the motor coil, completing the brushed motor coil. of commutation.

    ★What is phase sequence?

    Answer: The arrangement sequence of brushless motor coils.

    ★What is magnetic steel?

    Answer: Generally used to refer to magnetic materials with high magnetic field strength. Electric vehicle motors all use neodymium iron stilbene rare earth magnets.

    ★What is electromotive force?

    Answer: It is generated by the motor's rotor cutting the magnetic lines of force. Its direction is opposite to that of the external power supply, so it is called back electromotive force.

    ★What is a brushed motor?

    Answer: When the motor is working, the coil and commutator rotate, but the magnets and carbon brushes do not rotate. The alternating change in the direction of the coil current is accomplished by the commutator and brushes that rotate 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 motors and brushless motors. From the words, it can be seen that brush motors have carbon brushes, while brushless motors do not have carbon brushes.

    ★What is a low-speed brushed motor? What are the characteristics?

    Answer: In the electric vehicle industry, low-speed brushed motors refer to hub-type low-speed, high-torque, gearless transmission brushed DC motors. The relative speed of the motor's stator and rotor is the speed of the wheels. There are 5 to 7 pairs of magnets on the stator, and the number of slots in the rotor armature is 39 to 57. Since the armature winding is fixed within the wheel housing, heat is easily dissipated with the help of the rotating housing. The rotating shell is woven with 36 spokes, which is more conducive to heat conduction.

    ★What are the characteristics of brushed and toothed motors?

    Answer: Because there are brushes in brushed motors, the main hidden danger is "brush wear". Users should note that brushed motors are divided into two types: toothed and toothless. At present, many manufacturers choose brushed and toothed motors, which are high-speed motors. The so-called "toothed" means that the motor speed is lowered through a gear reduction mechanism (because the national standard stipulates that the speed of electric vehicles must not exceed 20 kilometers per hour, so the motor speed should be 170 rpm or so). Because the high-speed motor is reduced through gears, the rider feels strong power when starting and has strong climbing ability. However, the electric wheel hub is closed, and only lubricant is added before leaving the factory. It is difficult for users to perform daily maintenance, and the gear itself also suffers from mechanical wear. In about one year, due to insufficient lubrication, the wear of the gear increases, the noise increases, and the current decreases during use. increases, affecting motor and battery life.

    ★What is a brushless motor?

    Because the controller provides direct current in different current directions, it achieves alternating changes in the direction of the coil current in the motor. Brushless motors have no brushes or commutators between the rotor and stator.

    ★How to realize phase commutation of motor?

    Answer: When a brushless or brushed motor rotates, the energizing direction of the coils in the motor needs to be alternately changed so that the motor can rotate continuously. The commutation of brushed motors is completed by the phase commutator and brushes, while the brushless motors are completed by the controller.

    ★What is missing phase?

    Answer: One phase of the three-phase circuit of the brushless motor or brushless controller cannot work. Phase loss is divided into main phase loss and Hall phase loss. The symptoms include motor shaking and failure to work, or weak rotation and loud noise. It is easy for the controller to burn out when it is working in a phase-deficient state.

    ★What are the common types of motors?

    Answer: Common motors include: brushed geared hub motors, brushed geared hub motors, brushless geared hub motors, brushless geared hub motors, side-mounted motors, etc.

    ★How to distinguish high-speed and low-speed motors from the type of motor?

    Answer: A Brushed geared hub motors and brushless geared hub motors are high-speed motors;

    B Brush gearless hub motors and brushless gearless hub motors are low-speed motors.

    ★How is the power of the motor defined?

    Answer: The power of a motor refers to the ratio of the mechanical energy output by the motor to the electrical energy provided by the power supply.

    ★Why should we choose the power of the motor? What is the significance of choosing motor power?

    Answer: The selection of motor rated power is very important and complicated.

The problem. When the load is on, if the rated power of the motor is too large, the motor will often run at light load, and the capacity of the motor itself will not be fully utilized, turning it into a "big horse-drawn cart". At the same time, the motor's operating efficiency will be low and its performance will be poor, which will increase Running costs. On the other hand, if the rated power of the motor is required to be small, it will be a "little horse pulling a big cart". If the motor current exceeds the rated current, the internal losses of the motor will increase. When the efficiency is low, it is a trivial matter. The important thing is that it affects the life of the motor, even if the overload is not large. , the life of the motor will be greatly reduced; more overload will destroy the insulation performance of the motor's insulating material or even burn it out. Of course, if the rated power of the motor is small, it may not be able to pull the load at all, which will cause the motor to be in trouble for a long time.

    Damage due to overheating during startup. Therefore, the rated power of the motor should be selected strictly according to the operating conditions of the electric vehicle.

    ★Why do general brushless DC motors have three Halls?

    Answer: Briefly speaking, in order for a brushless DC motor to rotate, 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 the rotor's magnetic field. In order for the two magnetic fields to have an angle, the direction of the magnetic field of the stator coil must change to a certain extent. So how do you know to change the direction of the stator magnetic field? Then it depends on those three Halls. You can think of those three Halls as having the task of telling the controller when to change the direction of the current.

    ★What is the approximate range of power consumption of brushless motor Hall?

    Answer: The approximate power consumption range of the brushless motor Hall is 6m A-20m A.

    ★At what temperature can a general motor work normally? What is the maximum temperature that a 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, motor coils are wound by enameled wire. When the temperature of the enameled wire is higher than about 150 degrees, the paint film will fall off due to excessive temperature, causing the coil to short-circuit. When the coil temperature is above 150 degrees, the temperature shown by the motor housing is around 100 degrees, so based on its housing temperature, the maximum temperature the motor can withstand is 100 degrees.

    ★The temperature of the motor should be below 20 degrees Celsius, that is, the temperature of the motor end cover should be less than 20 degrees Celsius above the ambient temperature. But what is the reason why the motor heats up more than 20 degrees Celsius?

    Answer: The direct cause of motor heating is caused by high current. Generally, it may be caused by short circuit or open circuit of the coil, demagnetization of the magnet or low efficiency of the motor. The normal situation is that the motor runs with high current for a long time.

    ★What causes the motor to heat up? What is the process?

    Answer: When the motor is running under load, there is power loss in the motor, which will eventually turn into heat energy, which will cause the temperature of the motor to rise beyond the ambient temperature. The amount by which the motor temperature is higher than the ambient temperature is called temperature rise. Once the temperature rises, the motor must dissipate 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 dissipated, the motor temperature no longer increases, but maintains a stable temperature, that is, it is in a state of balance between heat generation and heat dissipation.

    ★What is the allowable temperature rise for a general click? Which part of the motor does the temperature rise of the motor have the greatest impact? How is it defined?

    Answer: When the motor is running under load, in order to maximize its function, the larger the load, that is, the output power, the better (if the mechanical strength is not considered). But the greater the output power, the greater the power loss, and the higher the temperature. We know that the weakest thing in the motor that can withstand temperature is the insulating material, such as enameled wire. There is a limit to the temperature resistance of insulating materials. Within this limit, the physical, chemical, mechanical, electrical and other aspects of the insulating materials are very stable, and their working life is generally about 20 years. Beyond this limit, the life of the insulating material is drastically shortened and may even burn out. This temperature limit is called the allowable temperature of the insulating material. The allowable temperature of the insulating material is the allowable temperature of the motor; the life of the insulating material is generally the life of the motor.

    The ambient temperature varies with time and location. When designing the motor, 40 degrees Celsius is stipulated as my country's standard ambient temperature. Therefore, the allowable temperature rise of the insulation material or motor minus 40 degrees Celsius is the allowable temperature rise.

    The allowable temperatures of different insulation materials are different. According to the allowable temperature, the five commonly used insulation materials for motors are A, E, B, F, and H. Calculated based on an ambient temperature of 40 degrees Celsius, these five insulation materials and their allowable temperatures and allowable temperature rises are as shown in the following table:

    Grade Insulating Material Allowable Temperature Allowable Temperature Rise

    A Impregnated cotton, silk, cardboard, wood, etc., ordinary insulating paint 105 65

    E Epoxy resin, polyester film, green shell paper, tri-acid fiber, highly insulating paint 120 80

    B Mica, asbestos, and glass fiber composition using organic paint with improved heat resistance as binder 130 90

    F Mica, asbestos and fiberglass composition bonded or impregnated with epoxy resin with excellent heat resistance 155 115

    H Mica, asbestos or fiberglass compositions bonded or impregnated with silicone and resin, silicone and rubber 180 140

    ★How to measure the phase angle of brushless motor?

    Answer: Turn on the power of the controller, and the controller supplies power to the Hall element, and the phase angle of the brushless motor can be detected. The method is as follows: Use the +20V DC voltage range of the multimeter, connect the red pen to the +5V line, and use the black pen to measure the high and low voltages of the three leads respectively, and compare them with the commutation tables of the 60-degree and 120-degree motors.

    ★Why can’t any brushless DC controller and brushless DC motor be connected at will and run normally? Why does brushless DC have reverse phase sequence?

    Answer: Generally speaking, the actual movement of a brushless DC motor is like this: the motor rotates----the direction of the rotor magnetic field changes----when the angle between the direction of the stator magnetic field and the direction of the rotor magnetic field reaches 60 degrees of electrical angle- --- Hall signal changes---- Phase line current direction changes---- The stator magnetic field moves forward across 60 degrees of electrical angle---- The angle between the direction of the stator magnetic field and the direction of the rotor magnetic field is 120 degrees of electrical angle--- - The motor continues to rotate. So we understand that Hall has six correct states. When a specific Hall tells the controller, the controller

There is a specific phase line output status. Therefore, the phase inversion sequence is to complete such a task, that is, to make the electrical angle of the stator always step in one direction by 60 degrees of electrical angle.

    ★What will happen if a 60-degree brushless controller is used on a 120-degree brushless motor? What about the opposite?

    Answer: It will cause phase loss and cannot rotate normally; but the controller used by Geneng is an intelligent brushless controller that can automatically identify 60-degree motors or 120-degree motors, so it can be compatible with both types of motors. Makes maintenance and replacement more convenient.

    ★How can the brushless DC controller and brushless DC motor have the correct phase sequence?

    Answer: The first step is to ensure that the power and ground wires of the Hall wire are plugged into the corresponding wires on the controller. There are 36 ways to connect the three motor Hall wires and the three motor wires to the controller. The final The simple but stupid way is to try each state one by one. You can do it without powering off when changing connections, but you must be careful and follow a certain order. Be careful not to turn too much each time. If the motor does not rotate smoothly, the state is incorrect. Turning the handle too much will damage the controller. If reverse rotation occurs, you need to know the phase sequence of the controller. In this case, the controller Hall lines a and c are interchanged, and the click lines A and B are interchanged to reverse the forward rotation. Finally, verify that the correct method of connection is used to ensure that it is normal during high current operation.

    ★How to control a 60-degree motor with a 120-degree brushless controller?

    Answer: Just add a direction line between the b-phase of the brushless motor Hall signal line and the controller sampling signal line.

    ★What is the intuitive difference between brushed high-speed motors and brushed low-speed motors?

    Answer: A. The high-speed motor has an overrunning clutch, which makes it easy to turn in one direction but hard to turn in the other direction; the low-speed motor can turn the bucket in both directions just as easily.

    B. A high-speed motor makes a louder noise when it rotates, while a low-speed motor makes less noise when it rotates. It is easy for experienced people to identify by ear.

    ★What is the rated operating status of the motor?

    Answer: When the motor is running, if all physical quantities are the same as its rated value, it is called the rated operating state. When working under the rated operating state, the motor can run reliably and have the best overall performance.

    ★How is the rated torque of the motor calculated?

    Answer: The rated torque output on the click shaft can be expressed by T2n. Its size is the output mechanical power rating divided by the transfer speed rating, that is, T2n=Pn. The unit of Pn is W and the unit of Nn is r/min. , The unit of T2n is N.M. If the unit of PNM is KN, the coefficient 9.55 is changed to 9550.

    Therefore, it can be concluded that if the rated power of the motor is equal, the lower the motor speed, the greater the torque.

    ★How is the starting current of the motor defined?

    Answer: It is generally required that the starting current of the motor cannot exceed 2 to 5 times its rated current. This is also an important reason why current limiting protection is provided on the controller.

    ★Why are the motor speeds sold on the market getting higher and higher? And what is the impact?

    Answer: ★Increasing speed on the part of the supplier can reduce costs. It is also a low-speed click. The higher the speed, the fewer turns of the coil. It also saves silicon steel sheets and reduces the number of magnets. Buyers think that high speed is better.

    ★When working at rated speed, its power remains unchanged, but its efficiency is obviously low in the low speed zone, which means it is unable to start.

    ★The efficiency is low, it requires a large current to start, and the current is also large when riding. It requires a large current limit on the controller and is not good for the battery.

    ★ How to repair the motor if it is abnormally hot?

    Answer: The maintenance method is generally to replace the motor or perform maintenance.

    ★When the no-load current of the motor is greater than the limit data in the reference table, it indicates that the motor has failed. What are the reasons? How to repair

    Answer: The internal mechanical friction of the click is large; the coil is partially short-circuited; the magnet is demagnetized; the DC motor phase commutator has carbon deposits. Maintenance methods are generally to replace the motor or replace the carbon brush and clean the carbon deposits.

    ★What is the maximum fault-free no-load current of various motors?

    Motor type When rated voltage is 24V When rated voltage is 36V

    Side-mounted motor 2.2A 1.8A

    High speed brushed motor 1.7A 1.0A

    Low speed brushed motor 1.0A 0.6A

    High speed brushless motor 1.7A 1.0A

    Low speed brushless motor 1.0A 0.6A

    ★How to measure the motor idling current?

    Answer: Set the multimeter to the 20A level, and connect the red and black test leads to the power input end of the controller. Turn on the power, and when the motor is not rotating, record the maximum current A1 of the multimeter at this time. Turn the handle to make the motor rotate at high speed without load for more than 10 seconds. After the motor speed stabilizes, start to observe and record the maximum value A2 of the multimeter at this time. Motor no-load current =A2-A1.

    ★Comparison of commonly used motors for electric vehicles:

    Motor type Transmission type Motor efficiency Climbing performance Maintenance cycle Volume Maintenance content Noise Cost

    Brushless toothless Brushless low-speed external rotor motor, direct drive 〉80% General None Large None Small Low

    Brushless toothed high-speed brushless motor, planetary gear reduction 〉 83% good about 3 years small lubricated gear medium high

    Brushed and toothed High-speed brushed motor, 2-stage gear reduction 〈 78% good about 1 year Large Replace carbon brushes, lubricate gears Large High

    Brushless toothed low-speed brushed external rotor motor, direct drive 〈 76% difference about 2 years Small Replace carbon brushes and clean carbon deposits Small Low

    ★How to identify the quality of the motor? What parameters are key to look at?

    Answer: It mainly depends on the size of the no-load current and riding current, compared with the normal value, the level of motor efficiency and torque, as well as the noise, vibration and heat generation of the motor. The best way is to use a dynamometer to test the efficiency curve.

    ★ ★ What is the difference between 180W and 250W motors? What are the requirements for the controller?

    Answer: The 250W riding current is large and requires high power margin and reliability of the controller.

    ★Why does the riding current of an electric vehicle differ depending on the rating of the motor under standard conditions?

    Answer: As we all know, under standard conditions, based on the rated load of 160W, the riding current on a 250W DC motor is about 4-5A, while the riding current on a 350W DC motor is slightly higher. For example: if the battery voltage is 48V, two motors 250W and 350W

, its rated efficiency point is 80%, then the rated operating current of the 250W motor is about 6.5A, and the rated operating current of the 350W motor is about 9A. The efficiency point of a general motor is that the further the operating current deviates from the rated operating current, the smaller its value is. Under the same load of 4-5A, the efficiency of a 250W motor is 70% and the efficiency of a 350W motor is 60%. Under a load of 5A,

    The output power of 250W is 48V*5A*70%=168W

    The output power of 350W is 48V*5A*60%=144W

    In order to make the output power of the 350W motor reach 168W (almost the rated load) to meet the riding requirements, the only way to increase the power supply is to increase the efficiency point.

    ★Why in the same environment, the driving range of an electric vehicle with a 350W motor is shorter than that of an electric vehicle with a 250W motor?

    Answer: Because under the same environment, the riding current of an electric vehicle with a 350W motor is large, so with the same battery, its driving range will be shorter.

    ★How should electric moped manufacturers choose motors? On what basis should I choose a motor?

    Answer: For electric vehicles, the most critical factor in motor selection is the selection of motor rated power.

    Motor rated power selection is generally divided into three steps:

    The first step is to calculate the load power P

    The second step is to pre-select the rated power of the motor and others based on the load power.

    The third step is to check the pre-selected motor. Generally, the heating temperature rise is checked first, then the overload capacity is checked, and the starting capacity is checked if necessary. If all pass, the preselected motor is selected; if it fails, repeat the second step until it passes.

    It is important to avoid that the smaller the rated power of the motor is, the more economical it is to meet the load requirements.

    After the second step is completed, temperature correction must be performed according to the difference in ambient temperature. The rated power is based on the national standard ambient temperature of 40 degrees Celsius. If the ambient temperature is low or relatively high all year round, the rated power of the motor should be corrected to make full use of the motor's capacity in the future. For example, if the temperature is low all year round, the rated power of the motor should be higher than the standard Pn. On the contrary, if the temperature is high all year round, the rated power should be reduced.

    Generally speaking, when the ambient temperature is determined, the selection of the motor of an electric vehicle should be based on the riding state of the electric vehicle. The closer the riding state of the electric vehicle can bring the motor to the rated working state, the better, and the riding state of the electric vehicle is better. The driving status generally depends on the road conditions. If the road surface in Tianjin is flat, a low-power motor is sufficient; if a larger-power motor is used, it will cause a waste of energy and result in a short driving range. If there are many mountain roads in Chongqing, a motor with higher power is suitable.

    ★ ★ A 60-degree brushless DC motor is more powerful than a 120-degree brushless DC motor, right? Why?

    Answer: From the market, we found that there is such a fallacy when communicating with many customers! Think 60 degree motor is more powerful than 120 degree. We think this is probably a kind of propaganda from the manufacturer of 60-degree brushless motors. From the principle of brushless motor and the facts, it is actually a 60-degree motor or a 120-degree motor! The so-called degree is just used to tell the brushless controller when to turn on which two phase wires it is interested in. There is no saying that anyone is more powerful than anyone else! The same goes for 240 degrees and 300 degrees. No one is more powerful than the other.