This may be the most comprehensive article on motor knowledge, including the names and introductions of various parts of electric motor.
What is an electric motor? An electric motor is a component that converts battery electrical energy into mechanical energy to drive the rotation of the wheels of an electric vehicle.
What is a winding? The armature winding is the core part of a DC motor, which consists of coils made of copper enameled wire. When the armature winding rotates in the magnetic field of the motor, it generates electromotive force.
What is a magnetic field? A force field that occurs around permanent magnets or currents and encompasses all spaces where magnetic forces can reach or act upon.
What is magnetic field strength? In SI units (amperes per meter), it refers to the magnetic field strength at a distance of 1/2 meter from an infinitely long conductor carrying 1 ampere current; in CGS units (centimeters-grams-seconds) and in honor of Oersted's contribution to electromagnetism, it defines that at a distance of 0.2 centimeters from an infinitely long conductor carrying 1 ampere current, the magnetic field strength is equal to 10e (Oersted), where 10e=1/4.103/m . Magnetic field strength is usually represented by H.
What is Ampère's rule? By holding onto a wire with your right hand and aligning your extended thumb with the direction of current flow, then the direction pointed by bent fingers represents the direction in which magnetic lines surround.
What is flux? Flux, also known as magnetic flux or magnetic flux density: In a uniform magnetic field, if there exists a plane perpendicular to its direction with area S and magnet induction intensity B, we define their product as flux passing through this plane.
What are stators? The stationary parts during operation for brushed or brushless motors. The motor shafts for hub-type brushed or brushless toothless motors are called stators, and this type of motor is referred to as an internal stator motor.
What are rotors? The rotating parts during operation for brushed or brushless motors. The casings for hub-type brushed or brushless toothless motors are called rotors, and this type of motor is referred to as an external rotor motor.
9.What are carbon brushes? They are placed on the surface of the commutator in a brushed motor. When the motor rotates, they transfer electrical energy to the coils through the commutator. Since their main component is carbon, they are called carbon brushes and tend to wear out easily. Regular maintenance and replacement should be performed, along with cleaning off accumulated carbon deposits.
10.What is a brush holder? A mechanical groove inside a brushed motor that holds and maintains the position of carbon brushes.
11.What is a commutator? In a brushed motor, it refers to metal surfaces arranged in strips that have mutual insulation properties. As the rotor of the motor rotates, these strip-like metals alternately contact positive and negative brushes, causing alternating changes in current direction in the coils of the brushed motor (commutation).
12.What is phase sequence? The arrangement order of coils in a brushless motor.
13.What is magnetic steel? It generally refers to magnetic materials with high magnetic field strength; rare earth magnet neodymium iron boron magnets are used in electric vehicle motors.
14.What is electromotive force (EMF)? Generated by cutting magnetic lines with the rotor of an electric machine; its direction opposes that of an external power source, hence it's called counter-electromotive force.
15.What is a brushed DC Motor? During operation, while coils and commutators rotate, magnets and carbon brushes do not rotate; alternating changes in coil current direction rely on rotating commutators and brushes attached to them. In electric vehicle industry there are high-speed brushed DC motors and low-speed brushed DC motors. There are many differences between brushed and brushless motors, as the name suggests, a brushed motor has carbon brushes while a brushless motor does not have carbon brushes.
What is a low-speed brushed motor? What are its characteristics? In the electric vehicle industry, a low-speed brushed motor refers to a hub-type, low-speed, high-torque brushed DC motor with no gear transmission. The relative rotational speed of the motor's stator rotor is the wheel speed. There are 5-7 pairs of magnets on the stator and 39-57 slots on the rotor armature. Since the armature winding is fixed inside the wheel shell and heat can be easily dissipated through the rotating shell, which is woven with 36 spokes that facilitate heat conduction.
Characteristics of brushed toothed motors? The main drawback of brushed motors lies in "brush wear". Users should note that there are two types of brushed motors: toothed and non-toothed. Currently, many manufacturers choose brushed toothed motors, which are high-speed motors. The term "toothed" means that by using a gear reduction mechanism, the motor speed can be lowered (as per national standards for electric vehicles where maximum speed should not exceed 20 km/hour; therefore, motor speed should be around 170 rpm).
Since it is a high-speed motor reduced by gears, its characteristics include strong power during startup and good climbing ability for riders. However, electric hub wheels are sealed and only lubricated before leaving factory making it difficult for users to perform regular maintenance. Additionally, gears themselves experience mechanical wear over time due to insufficient lubrication after about one year leading to increased noise levels and current consumption during use thereby affecting both motor and battery life.
18.What is a brushless motor? A brushless motor does not have brushes or commutators between its rotor and stator as different currents in various directions provided by controllers achieve alternating changes in coil current direction within the motor.
19. How does a motor achieve commutation? In brushed or brushless motors, the direction of current in the coils inside the motor needs to alternate during rotation to enable continuous operation. Brushed motors rely on commutators and brushes for commutation, while brushless motors rely on controllers for this purpose.
20. What is phase loss? In a three-phase circuit of a brushless motor or controller, one phase fails to work properly. Phase loss can be categorized as main phase loss and Hall sensor phase loss. It manifests as motor shaking without functioning or weak rotation with high noise levels. Operating a controller under phase loss conditions can easily lead to burnout.
What are the common types of motors? Common types of motors include: brushed geared hub motor, brushed gearless hub motor, brushless geared hub motor, brushless gearless hub motor, and side-mounted motor.
22. How to differentiate between high-speed and low-speed motors based on their types? A. Brushed geared hub motor and brushless geared hub motor belong to high-speed motors; B. Brushed gearless hub motor and brushless gearless hub motor belong to low-speed motors.
23. How is the power of a motor defined? The power of a motor refers to the ratio between the mechanical energy output by the motor and the electrical energy provided by the power source.
24. Why choose the power of the motor? What is the significance of choosing the power of the motor? The selection of rated power for motors is a very important and complex issue. When under load, if the rated power of the motor is too large, it will often operate in light load conditions, and its capacity cannot be fully utilized, resulting in inefficiency and poor performance, which will increase operating costs.
On the other hand, if the required rated power for a motor is too small, it will result in "a small horse pulling a big cart". The motor current exceeds its rated current, increasing internal losses and reducing efficiency. More importantly, it affects the lifespan of the motor. Even with only slight overload, there will be a significant reduction in lifespan; with excessive overload, it can damage insulation materials or even cause burnout. Of course, if the rated power of a motor is too small to drive loads at all, it may remain in startup mode for an extended period and overheat to failure. Therefore, it is necessary to strictly select the rated power based on actual operating conditions.
Why do general brushless DC motors have three Hall sensors? In brief terms: In order for brushless DC motors to rotate properly,the magnetic field between stator coils and rotor permanent magnets must maintain a certain angle difference at all times.The process by which this occurs corresponds to changes in rotor magnetic field direction.To ensure that both fields maintain their respective angles during rotation,the direction of stator coil's magnetic field must change after reaching a certain point.However,it requires knowing when exactly should we change this direction.That's where those three Hall sensors come into play.They are responsible for informing controllers when to change current directions.
26.What is approximately range consumption level for brushless DC motors' Hall sensors? Approximately 6mA-20mA.
27.At what temperature can general motors operate normally? What maximum temperature can they withstand?
If the measured temperature of a motor's casing exceeds 25 degrees Celsius above ambient temperature, it indicates that the motor's temperature rise has exceeded normal limits. Generally, the temperature rise of a motor should be below 20 degrees Celsius. Motor coils are typically wound with enameled wire, and when the temperature exceeds around 150 degrees Celsius, the enamel coating will peel off due to excessive heat, causing coil short circuits. When the coil temperature is above 150 degrees Celsius, the surface temperature of the motor housing is around 100 degrees Celsius. Therefore, if we base it on housing temperatures,the maximum operating temperature for motors would be about 100 degrees Celsius.
28.The motor's operating temperature should be below 20 degrees Celsius; in other words,the difference between its end cap and ambient temperatures should not exceed 20 degrees Celsius.But what causes a motor to generate heat beyond this threshold?
The direct cause of motor heating is usually due to high current flow.It can result from various factors such as coil short or open circuits,demagnetization of magnetic steel or low efficiency.Normal situations involve prolonged operation under heavy currents.
29. What causes a motor to generate heat? What kind of process does this entail?
When running under load,motors experience power losses which ultimately convert into thermal energy.
This raises their internal temperatures above ambient levels.The difference between their actual temperatures and ambient ones is referred to as "temperature rise".Once there is an increase in temperate,a motor needs to dissipate heat into its surroundings;the higher its internal temperture,the faster it dissipates.When a motors' rate at which it emits heat equals that at which it dissipates,it reaches equilibrium where its temprature no longer increases but remains stable.This state represents balance between generation and dissipation of heat.
What is the general allowable temperature rise when clicked? Which part of the motor does the temperature rise have the greatest impact on? How is it defined? When the motor load is running, it should maximize its effect, and the larger the output power of the load, the better (if mechanical strength is not considered). However, as output power increases, so does power loss and temperature. We know that insulation materials such as enameled wire are the weakest in terms of temperature resistance inside a motor. Insulation materials have a limit to their temperature resistance. Within this limit, various aspects of physical, chemical, mechanical, and electrical properties of insulation materials remain stable and their service life is generally about 20 years.
Beyond this limit, the service life of insulation materials dramatically shortens or even leads to burnout. This temperature limit is called the allowable temperature for insulation materials. The allowable temperature for insulation materials is also referred to as the allowable temperature for motors; while service life of insulation material generally represents motor's lifespan.
Environmental temperatures vary with time and location. When designing motors in China, 40 degrees Celsius is set as standard environmental temperature. Therefore, subtracting 40 degrees Celsius from either insulating material's or motor's allowable temperatures gives us permissible temperate rise (allowable increase in heat). Different insulating materials have different allowable temperatures; commonly used insulating materials for motors are A、E、B、F、H.
Based on an ambient temperature calculation at 40 degrees Celsius , below shows these five types of insulating material along with their respective allowed temperatures and permissible temperate rises: corresponding levels/insulating material/allowed temperatures/permissible temperate rises. A - Impregnated cotton,silk,paperboard,and wood etc., ordinary insulating varnish - 105°C -65°C E - Epoxy resin,polyester film,mica paper,triple acid fiber，highly insulating varnish - 120°C -80°C B - Mica, asbestos, and glass fiber composites bonded with organic paint that has improved heat resistance performance - 130°C -90°C F - Mica, asbestos, and glass fiber composites bonded or impregnated with excellent heat-resistant epoxy resin- 155°C-115°C H – Mica, asbestos or glass fiber composites bonded or impregnated with silicone resin，silicone rubber-180℃-140℃
How to measure the phase angle of a brushless motor? Connect the power supply of the controller and provide power to the Hall elements by the controller to detect the phase angle of the brushless motor. The method is as follows: Use a multimeter's +20V DC voltage range and connect the red probe to +5V line. Measure the high and low voltages of three leads respectively using black probes. Then compare them with commutation table for 60 degrees and 120 degrees.
32. Why can't any random combination of a brushless DC controller and a brushless DC motor make it rotate normally? Why is there talk about reverse phase sequence in brushless DC motors? Generally speaking, during actual motion process of a brushless DC motor: Motor rotates —— Rotor magnetic field direction changes —— When angle between stator magnetic field direction and rotor magnetic field direction reaches 60 electrical degrees —— Hall signal changes —— Phase current direction changes—— Stator magnetic field crosses over forward by 60 electrical degrees—— Angle between stator magnetic field direction and rotor magnetic field direction becomes 120 electrical degrees—— Motor continues rotating.
In this way we understand that there are six correct states for Hall sensors. When specific Hall sensor informs the controller accordingly, then specific output state for each phase will be generated by controller. Therefore, reverse phase sequence aims to accomplish such a task, which is to make the stator's electrical angle always step forward in one direction by 60 electrical degrees.
What happens if a 60 degree brushless controller is used on a 120 degree brushless motor? And vice versa? Both will be inverted to the phenomenon of missing phase, can not rotate normally; but the controller used by Jiehnen is an intelligent brushless controller can automatically recognize the 60 degree motor or 120 degree motor, so that it can be compatible with two kinds of motors, which makes it more convenient for maintenance and replacement.
34. How to reverse the correct phase sequence of DC brushless controller and DC brushless motor? The first step is to make sure that the power and ground wires of the Hall line and the corresponding line on the controller are plugged in well, and there are 36 kinds of connection methods between the Hall line of the three motors and the three motor wires to the controller, and the simplest and stupidest method is to test each kind of state one by one. Switching can be done without power, but must be careful, but also in a certain order. Be careful not to turn each time too big, if the motor rotation is not smooth, then this state is not right, turn the screw too big on the damage to the controller, if there is a reversal of the situation, in the case of knowing the phase sequence of the controller is the controller Hall line a, c interchangeable, click on the line A phase and the B phase to change, can be reversed for positive rotation. The final verification of the correct method of connection is normal when running at high current.
35. How to control 60 degree motor with 120 degree brushless controller? Add the direction line between the Hall signal line of brushless motor and the sampling signal line of controller.
36.What is the intuitive difference between a brushed high speed motor and a brushed low speed motor? A. High-speed motors have overrunning clutches, so it is easy to turn in one direction and exhausting to turn in the other direction; low-speed motors turn the bucket in both directions just as easily. B. High-speed motors make more noise when turning, while low-speed motors make less noise. Experienced people can easily recognize them by ear.
37. What is the rated operating condition of a motor? When the motor is running, if all the physical quantities are the same as its rated value, it is called the rated operating condition. Working under the rated operating condition, the motor can run reliably and has the best overall performance.
38. How is the rated torque of a motor calculated? The rated torque output on the click shaft can be expressed by T2n, the size of which is the rated value of the output mechanical power divided by the rated value of the forwarding speed, i.e., T2n=Pn where the unit of Pn is W, the unit of Nn is r/min, and the unit of T2n is N.M, and the coefficient of 9.55 is changed to 9550 if the unit of PNM is KN.
Therefore, it can be concluded that if the motor rated power is equal, the lower the speed of the motor, the greater the torque.
How is the starting current of a motor defined? Generally, the starting current of the motor should not exceed 2~5 times of its rated current, which is also an important reason why the current limitation protection is applied to the controller.
40. Why is the speed of motors sold on the market getting higher and higher? And what is the impact? Supplier side of the speed can reduce costs, the same is a low-speed click, high speed coil turns will be less, but also save the silicon steel sheet, the number of magnets is also less, the buyer that high-speed is good.
Rated speed work, its power is unchanged, but in the low-speed zone when the efficiency is significantly lower, that is, start weak.
Low efficiency, need to use high current to start, ride the current is also large, the current limiting requirements of the controller is large, and the battery is not good.
How to repair the abnormal heating of the motor? Maintenance is generally dealt with by replacing the motor, or maintenance 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 is faulty, what are the reasons? How to repair? Click on the internal mechanical friction; coil local short circuit; magnet demagnetization; DC motor phase converter carbon. Maintenance and treatment methods generally that for the replacement of the motor, or replace the carbon brushes, clean up the carbon buildup.
43.What is the maximum fault-free no-load current of various motors? The following corresponds to the form of motor, rated voltage 24V, rated voltage 36V: Side-mounted motor 2.2A 1.8A High-speed brush motor 1.7A 1.0A Low-speed brush 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 idle current? Place the multimeter at 20A, and connect the red and black pens to the power input of the controller. Turn on the power and record the maximum current A1 of the multimeter when the motor is not rotating. Turn the handle, so that the motor high-speed no-load rotation for more than 10s, waiting for the motor speed stabilization, began to observe and record the maximum value of the multimeter A2. Motor no-load current = A2-A1.
45. How to recognize the motor is good or bad? What are the key parameters? The main parameters are the size of no-load current and riding current, compared with the normal value, and the efficiency and torque of the motor, 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 controller requirements? The 250W has a high riding current and requires a higher power margin and reliability of the controller.
47. Why does the riding current of an e-bike under standard conditions vary depending on the motor rating? As we all know, under standard conditions, with a rated load of 160W, the riding current on a 250W DC motor is about 4 - 5A, while on a 350W DC motor the riding current is slightly higher.
For example, if the battery voltage is 48V, and two motors, 250W and 350W, have a rated efficiency point of 80%, then the rated operating current of the 250W motor will be about 6.5A, while the rated operating current of the 350W motor will be about 9A.
In general, the efficiency point of a motor is smaller the farther the working current deviates from the rated working current.
Under the same load condition of 4-5A, the efficiency of a 250W motor is 70%, and the efficiency of a 350W motor is 60%, then under the load condition of 5A, the output power of a 250W motor is 48V.
The output power of 250W is 48V5A70%=168W.
The output power of 350W is 48V5A60%=144W.
For a 350W motor, the only way to get the output power to meet the cycling requirements, i.e., to reach 168W (almost the rated load), is to increase the power supply, thus increasing the efficiency point.
Why does a 350W motor have a shorter range than a 250W motor in the same environment? Because under the same environment, the electric bicycle with 350W motor rides with high current, so under the same situation of battery, its mileage will be shorter.
How to choose the motor for electric scooter manufacturers? What is the basis for motor selection? The most critical factor in the selection of motors for electric vehicles is the selection of motor power rating.
The selection of motor power rating is generally divided into three steps: The first step is to calculate the load power P The second step is to pre-select the motor's power rating and others according to the load power. The third step, calibrate the pre-selected motor.
Generally calibrated first heat temperature rise, and then calibrated overload capacity, if necessary, calibrated starting ability. Passed, the pre-selected motor will be selected; not pass from the second step to re-run, until it passes. Do not meet the requirements of the load, the smaller the rated power of the motor the more economical.
After the second step is done, according to the different ambient temperatures for temperature correction, the rated power is in the national standard ambient temperature of 40 degrees Celsius under the premise. If the ambient temperature is low or high all year round, the future full use of the motor's capacity, the rated power of the motor should be corrected.
For example, if the perennial temperature is low, the rated power of the motor century should be higher than the standard Pn, on the contrary, if the perennial temperature is high, the rated power should be reduced.
In general, in the case of the ambient temperature is determined, the choice of electric car motor should be based on the riding state of the electric car to determine the riding state of the electric car, the more the electric car can make the motor close to the rated state of work, the better, and the riding state of the electric car is generally based on the road conditions.
If the road surface is smooth in Tianjin, the small power motor is enough; if you want to use a larger power motor, it will cause waste of energy, resulting in a short range. If there are many mountainous roads in Chongqing, it is suitable to use a higher power motor.
50. 60 degree DC brushless motor is more powerful than 120 degree DC brushless motor, right? Why? From the market found in communication with many customers, there is a common fallacy! Thinking that 60 degrees motor is more powerful than 120 degrees.
From the principle of the brushless motor and the facts prove that, in fact, 60 degrees motor or 120 degrees motor! The so-called degree is only used to tell the brushless controller when to let the thought of which two phase wire conduction only. There is no one more powerful than the other! 240 degrees and 300 degrees is the same, there is no one more powerful than the other.
