The safe operation of the generator plays a decisive role in ensuring the normal operation and power quality of the power system, and the generator itself is also a very valuable electrical component. Therefore, a relay protection device with perfect performance should be installed for various faults and abnormal operating conditions. Let’s learn about the basic knowledge about generators!

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1. What is a motor? The motor is a component that converts battery electrical energy into mechanical energy and drives the wheels of an electric vehicle to rotate.

2. What is winding? The armature winding is the core part of the DC motor, which is a coil wound by copper enameled wire. When the armature winding rotates in the magnetic field of the motor, an electromotive force is generated.

3. What is a magnetic field? The force field generated around a permanent magnet or electric current and the space or range of magnetic force that can be reached by magnetic force.

4. What is the magnetic field strength? 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 is 1 A/m (amperes/meter, SI); in CGS units (centimeter-gram-second), is To commemorate Oersted’s contribution to electromagnetism, define 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 to be 10e (Oersted), 10e=1/4.103/m, and the magnetic field strength is usually used H said.

5. What is Ampere’s law? Hold the wire with your right hand, and make the direction of the straight thumb coincide with the direction of the current, then the direction pointed by the bent four fingers is the direction of the magnetic induction line.

6. What is magnetic flux? 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 of the magnetic field is B, and the area of ​​the plane is S. We define the product of the magnetic induction B and the area S, which is called passing through this surface of magnetic flux.

7. What is a stator? The part that does not rotate when the brushed or brushless motor is working. The motor shaft of the hub-type brushed or brushless gearless motor is called the stator, and this type of motor can be called an inner stator motor.

8. What is a rotor? The part that turns when a brushed or brushless motor works. The shell of the hub-type brushed or brushless gearless motor is called the rotor, and this type of motor can be called an outer rotor motor.

9. What is a carbon brush? The inside of the brushed motor is on the surface of the commutator. When the motor rotates, the electric energy is transmitted to the coil through the phase commutator. Because its main component is carbon, it is called a carbon brush, which is easy to wear. It should be regularly maintained and replaced, and carbon deposits should be cleaned

10. What is a brush grip? A mechanical guide that holds and holds the carbon brushes in place in a brushed motor.

11. What is a phase commutator? Inside the brushed motor, there are strip-shaped metal surfaces that are insulated from each other. When the motor rotor rotates, the strip-shaped metal alternately contacts the positive and negative poles of the brush to realize the alternating positive and negative changes in the direction of the motor coil current and complete the replacement of the brushed motor coil. Mutually.

12. What is phase sequence? The arrangement order of brushless motor coils.

13. What is a magnet? It is generally used to refer to magnetic materials with high magnetic field strength. Electric vehicle motors use NdFeR rare earth magnets.

14. What is electromotive force? It is generated by the rotor of the motor cutting the magnetic force line, and its direction is opposite to that of the external power supply, so it is called counter electromotive force.

15. What is a brushed motor? When the motor is working, the coil and commutator rotate, and the magnetic steel and carbon brushes do not rotate. The alternating change of the coil current direction is accomplished by the commutator and brushes that rotate with the motor. In the electric vehicle industry, brushed motors are divided into high-speed brushed motors and low-speed brushed motors. There are many differences between brushed motors and brushless motors. It can be seen from the words that brushed motors have carbon brushes, and brushless motors do not have carbon brushes.

16. What is a low-speed brushed motor? What are the characteristics? In the electric vehicle industry, a low-speed brushed motor refers to a hub-type low-speed, high-torque gearless brushed DC motor, and the relative speed of the stator and rotor of the motor is the speed of the wheel. There are 5~7 pairs of magnetic steel on the stator, and the number of slots in the rotor armature is 39~57. Since the armature winding is fixed in the wheel housing, the heat is easily dissipated by the rotating housing. The rotating shell is woven with 36 spokes, which is more conducive to heat conduction. Jicheng training micro-signal is worthy of your attention!

17. What are the characteristics of brushed and toothed motors? Because there are brushes in the brushed motor, the main hidden danger is “brush wear”. Users should notice that there are two types of brushed motors: toothed and toothless. At present, many manufacturers choose brushed and toothed motors, which are high-speed motors. The so-called “toothed” means to reduce the motor speed through the gear reduction mechanism (because the national standard stipulates that the speed of electric vehicles should not exceed 20 kilometers per hour, the motor speed should be at 170 rpm/about).

Since the high-speed motor is decelerated by gears, it is characterized in that the rider feels strong power when starting, and has strong climbing ability. However, the electric wheel hub is closed, and it is only filled with lubricant before leaving the factory. It is difficult for users to perform daily maintenance, and the gear itself is also mechanically worn. Insufficient lubrication will lead to increased gear wear, increased noise, and low current during use. Increase, affecting motor and battery life.

18. What is a brushless motor? Since the controller provides direct current with different current directions to achieve the alternating change of the coil current direction in the motor. There are no brushes and commutators between the rotor and stator of brushless motors.

19. How does the motor achieve commutation? When the brushless or brushed motor is rotating, the direction of the coil inside the motor needs to be alternately switched, so that the motor can rotate continuously. The commutation of the brushed motor is completed by the commutator and the brush, and the brushless motor is completed by the controller

20. What is lack of phase? In the three-phase circuit of the brushless motor or brushless controller, one phase cannot work. Phase loss is divided into main phase loss and Hall phase loss. The performance is that the motor shakes and cannot work, or the rotation is weak and the noise is loud. It is easy to burn out if the controller works in the state of lack of phase.

21. What are the common types of motors? Common motors are: hub motor with brush and gear, hub motor with brush and gearless, brushless hub motor with gear, brushless hub motor without gear, side-mounted motor, etc.

22. How to distinguish high and low speed motors from the type of motor? A brushed and geared hub motors, brushless geared hub motors are high-speed motors; B brushed and gearless hub motors, brushless and gearless hub motors are low-speed motors.

23. How is the power of the motor defined? The power of the motor refers to the ratio of the mechanical energy output by the motor to the electrical energy provided by the power supply.

24. Why choose the power of the motor? What is the significance of choosing motor power? The choice of motor rated power is a very important and complicated issue. When under load, 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 utilized, turning into a “big horse-drawn cart”. At the same time, the motor’s low operating efficiency and poor performance will increase running costs.

Conversely, the rated power of the motor is required to be small, that is, a “small horse-drawn cart”, the motor current exceeds the rated current, the internal consumption of the motor increases, and when the efficiency is low, the important thing is to affect the life of the motor, even if the overload is not much , the life of the motor will also be reduced more; more overload will damage the insulation performance of the motor insulation material or even burn it. 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 in the starting state for a long time and be overheated and damaged. Therefore, the rated power of the motor should be selected strictly according to the operation of the electric vehicle.

25. Why do general DC brushless motors have three Halls? Briefly speaking, in order for the 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 permanent magnet of the rotor. The process of rotor rotation is also the process of changing the direction of the rotor magnetic field. In order to make the two magnetic fields have an angle, the magnetic field direction 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 rely on the three halls. Think of those three Halls as having the task of telling the controller when to change the direction of the current.

26. What is the approximate range of power consumption of the brushless motor Hall? The power consumption of brushless motor Hall is roughly in the range of 6mA-20mA.

27. At what temperature can a general motor work normally? What is the maximum temperature the motor can withstand? If the measured temperature of the motor cover exceeds the ambient temperature by more than 25 degrees, it indicates 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 made of enameled wire, and when the temperature of the enameled wire is higher than about 150 degrees, the paint film will fall off due to the high temperature, resulting in a short circuit of the coil. When the coil temperature is above 150 degrees, the motor casing exhibits a temperature of about 100 degrees, so if the casing temperature is used as the basis, the maximum temperature the motor can withstand is 100 degrees.

28. 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 when it exceeds the ambient temperature, but what is the reason for the motor to heat more than 20 degrees Celsius? The direct cause of the motor heating is due to the large current. Generally, it may be caused by short circuit or open circuit of the coil, demagnetization of the magnetic steel or low efficiency of the motor. The normal situation is that the motor runs at a high current for a long time.

29. What causes the motor to heat up? What kind of process is this? When the motor load is running, there is power loss in the motor, which will eventually turn into heat energy, which will increase the temperature of the motor and exceed the ambient temperature. The value by which the motor temperature rises above the ambient temperature is called warm-up. Once the temperature rises, the motor will 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 temperature of the motor will not increase, but maintain a stable temperature, that is, in a state of balance between heat generation and heat dissipation.

30. What is the allowable temperature rise of the general click? Which part of the motor is most affected by the temperature rise of the motor? How is it defined? When the motor is running under load, starting from its function as much as possible, the higher the load, that is, the output power, the better (if mechanical strength is not considered). However, the greater the output power, the greater the power loss, and the higher the temperature. We know that the weakest temperature-resistant thing in the motor 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 insulating materials are very stable, and their working life is generally about 20 years.

If this limit is exceeded, the life of the insulating material will be shortened sharply, and it may even be burned. 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 place. When designing the motor, it is stipulated that 40 degrees Celsius is taken as the standard ambient temperature in my country. Therefore, the allowable temperature of the insulating material or motor minus 40 degrees Celsius is the allowable temperature rise. The allowable temperature of different insulating materials is different. According to the allowable temperature, the commonly used insulating materials for motors are A, E, B, F, H five kinds.

Calculated based on the ambient temperature of 40 degrees Celsius, the five insulating materials and their allowable temperatures and allowable temperature rises are shown below, corresponding to grades, insulating materials, allowable temperatures, and allowable temperature rises. A impregnated cotton, silk, cardboard, wood, etc., ordinary insulating paint 105 65E epoxy resin, polyester film, green shell paper, triacid fiber, high insulating paint 120 80 B organic paint with improved heat
resistance Mica, asbestos, and glass fiber composition as adhesive 130 90
F Mica, asbestos, and glass fiber composition bonded or impregnated with epoxy resin with excellent heat resistance 155 115
H Bonded or impregnated with silicone resin Compositions of mica, asbestos or fiberglass, silicon rubber 180 140

31. How to measure the phase angle of the brushless motor? Turn on the power supply of the controller, and the controller supplies power to the Hall element, and then 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 test lead to the +5V line, and the black pen to measure the high and low voltages of the three leads, and compare them with the commutation tables of the 60-degree and 120-degree motors.

32. Why can’t any brushless DC controller and brushless DC motor be connected at will to rotate normally? Why does brushless DC have the theory of reverse phase sequence?  Generally speaking, the actual movement of the brushless DC motor is such a process: 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 electrical angle – the Hall signal changes – - The direction of the phase current changes – The stator magnetic field spans 60 degrees electrical angle forward – The angle between the stator magnetic field direction and the rotor magnetic field direction is 120 degrees electrical angle – The motor continues to rotate.

So we understand that there are six correct states for Hall. When a specific hall tells the controller, the controller has a specific phase output state. Therefore, the phase inversion sequence is to complete such a task, that is, to make the electrical angle of the stator always step by 60 degrees in one direction.

33. What happens if a 60-degree brushless controller is used on a 120-degree brushless motor? What about vice versa? It will be reversed to the phenomenon of phase loss and cannot rotate normally; but the controller adopted by Geneng is an intelligent brushless controller that can automatically identify the 60-degree motor or the 120-degree motor, so that it can be compatible with the two kinds of motors, making maintenance It is more convenient to replace.

34. How can brushless DC controller and brushless DC motor get the correct phase sequence? The first step is to ensure that the power wires and ground wires of the Hall wires 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, which is the simplest and most convenient. The dumb way is to try each state one by one. Switching can be done without power on, but it must be done carefully and in a certain order. Be careful not to turn too much each time. If the motor does not rotate smoothly, this state is wrong. If the turn is too large, the controller will be damaged. If there is a reversal, after knowing the phase sequence of the controller In this case, exchange the Hall wires a and c of the controller, click on the line A and phase B to exchange each other, and then reverse to forward rotation. Finally, the correct way to verify the connection is that it is normal during high current operation.

35. How to control a 60-degree motor with a 120-degree brushless controller? Just add a direction line between the phase b of the Hall signal line of the brushless motor and the sampling signal line of the controller.

36. What is the intuitive difference between a brushed high-speed motor and a brushed low-speed motor? A. The high-speed motor has an overrunning clutch. It is easy to turn in one direction, but it is exhausting to turn in the other direction; the low-speed motor is as easy as turning the bucket in both directions. B. The high-speed motor makes a lot of noise when turning, and the low-speed motor makes less noise. Experienced people can easily recognize it by ear.

37. What is the rated operating state of the motor? When the motor is running, if each physical quantity is the same as its rated value, it is called the rated operating state. Working under the rated operating state, the motor can run reliably and have the best overall performance.

38. How is the rated torque of the motor calculated? The rated torque output on the click shaft can be represented by T2n, which is the rated value of the output mechanical power divided by the rated value of the transfer speed, that is, T2n=Pn where the unit of Pn is W, the unit of Nn is r/min, T2n The unit is NM, if the PNM unit 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 speed of the motor, the greater the torque.

39. How is the starting current of the motor defined? It is generally required that the starting current of the motor should not exceed 2 to 5 times of its rated current, which is also an important reason for the current limiting protection on the controller.

40. Why are the speeds of motors sold in the market getting higher and higher? and what is the impact? Suppliers can reduce costs by increasing the speed. It is also a low-speed click. The higher the speed, the fewer coil turns, the silicon steel sheet is saved, and the number of magnets is also reduced. Buyers think that high speed is good.

When working at the rated speed, its power remains the same, but the efficiency is obviously low in the low speed area, that is, the starting power is weak.

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

41. How to repair the abnormal heating of the motor? The method of maintenance and treatment is generally to replace the motor, or to carry out maintenance and warranty.

42. When the no-load current of the motor is greater than the limit data of the reference table, it indicates that the motor has failed. What are the reasons? How to repair? Click the internal mechanical friction is large; the coil is partially short-circuited; the magnetic steel is demagnetized; the DC motor commutator has carbon deposits. The method of maintenance and treatment is generally to replace the motor, or replace the carbon brush, and clean up the carbon deposit.

43. What is the maximum limit no-load current without failure of various motors? The following correspond to the motor type, when the rated voltage is 24V, and when the 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

44. How to measure the idling current of the motor? Put the multimeter in the 20A position, and connect the red and black test leads to the power input terminal of the controller. Turn on the power, and record the maximum current A1 of the multimeter at this time when the motor does not rotate. Turn the handle to make the motor rotate at high speed with no load for more than 10s. 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.

45. How to identify the quality of the motor? What are the key parameters? It is mainly the size of no-load current and riding current, compared with the normal value, and the level of motor efficiency and torque, as well as the noise, vibration and heat generation of the motor. The best way is to test the efficiency curve with a dynamometer.

46. ​​What is the difference between 180W and 250W motors? What are the requirements for the controller? The 250W riding current is large, which requires high power margin and reliability of the controller.

47. Why in the standard environment, the riding current of the electric vehicle will be different due to the different ratings of the motor? As we all know, under standard conditions, calculated with a rated load of 160W, the riding current on a 250W DC motor is about 4-5A, and the riding current on a 350W DC motor is slightly higher.

For example: if the battery voltage is 48V, two motors are 250W and 350W, and their rated efficiency points are both 80%, then the rated operating current of the 250W motor is about 6.5A, while the rated operating current of the 350W motor is about 9A.

The efficiency point of a general motor is that the farther the operating current deviates from the rated operating current, the smaller the value is. In the case of a load of 4-5A, the efficiency of a 250W motor is 70%, and the efficiency of a 350W motor is 60%. 5A load,

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

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

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

48. Why is the mileage of electric vehicles with 350W motors shorter than those of 250W motors under the same environment? Due to the same environment, the 350W electric motor has a large riding current, so the mileage will be short under the same battery condition.

49. How should electric bicycle manufacturers choose motors? Based on what to choose a motor? For electric vehicles, the most critical factor in the selection of its motor is the selection of the rated power of the motor.

The selection of the rated power of the motor 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 according to the load power. The third step is to check the pre-selected motor.

Generally, check the heating and temperature rise first, then check the overload capacity, and check the starting capacity if necessary. If all pass, the pre-selected motor is selected; if not pass, start from the second step until pass. Do not meet the requirements of the load, the smaller the rated power of the motor, the more economical it is.

After the second step is completed, temperature correction should be carried out according to the difference in ambient temperature. The rated power is carried out under the premise that the national standard ambient temperature is 40 degrees Celsius. If the ambient temperature is low or high all the year round, the rated power of the motor should be corrected by making full use of the capacity of the motor in the future. For example, if the perennial temperature is low, the rated power of the motor should be higher than the standard Pn. On the contrary, if the perennial temperature is high, the rated power should be reduced.

Generally speaking, when the ambient temperature is determined, the motor of the electric vehicle should be selected according to the riding state of the electric vehicle. The riding state of the electric vehicle can make the motor close to the rated working state, the better. The traffic status is generally determined according to the road conditions. For example, if the road surface in Tianjin is flat, a low-power motor is enough; if a higher-power motor is used, energy will be wasted and the mileage will be short. If there are many mountain roads in Chongqing, it is suitable to use a motor with a larger power.

A 50.60 degree DC brushless motor is more powerful than a 120 degree DC brushless motor, right? Why? From the market, it is found that such a fallacy is common when communicating with many customers! Think 60 degree motor is stronger than 120 degree. From the principle of the brushless motor and the facts, it doesn’t matter whether it is a 60-degree motor or a 120-degree motor! The so-called degrees are only used to tell the brushless controller when to make the two phase wires it cares about conducting. There is no such thing as more powerful than anyone else! The same is true for 240 degrees and 300 degrees, no one is stronger than the other.

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Post time: Apr-12-2023