The most detailed introduction of electric bicycle motor

Electric Bike Motor

The most detailed introduction of electric bicycle motor

Electric Bike Motor

Electric bicycle motor refers to the drive motor used in electric bicycles. The form is different depending on the environment in which it is used and the frequency of use. Different types of motors have different characteristics. At present, permanent magnet DC motors are commonly used in electric vehicle motors. Electric motor motor is divided into two categories according to the power supply form of the motor. It can be divided into two types: brush motor and brushless motor. According to the mechanical structure of the motor assembly, it is generally divided into “toothed” (high motor speed, need to pass gear Deceleration) and “no teeth” (motor torque output does not undergo any deceleration) two categories.


1. Permanent magnet DC motor:
It consists of a stator pole, a rotor, a brush, a casing, and the like.
The stator poles are made of permanent magnets (permanent magnets) and are made of ferrite, aluminium-nickel-cobalt, neodymium-iron-boron or the like. According to its structural form, it can be divided into cylindrical type and tile type.
The rotor is generally laminated with silicon steel sheets, and the enameled wire is wound between the two slots of the rotor core (three slots have three windings), and the joints are respectively welded to the metal piece of the commutator.
The brush is a conductive component that connects the power supply to the rotor winding, and has both electrical and wear resistance properties. The brush of the permanent magnet motor uses a single metal sheet or a metal graphite brush or an electrochemical graphite brush.
2. Brushless DC motor:
It consists of a permanent magnet rotor, a multi-pole winding stator, a position sensor, and the like.
Brushless DC motors are characterized by brushless, semiconductor switching devices (such as Hall elements) for electronic commutation, that is, electronic switching devices replace traditional contact commutators and brushes. It has the advantages of high reliability, no commutation spark, and low mechanical noise.
The position sensor commutates the current of the stator winding in a certain order according to the change of the position of the rotor (ie, detects the position of the rotor pole relative to the stator winding, and generates a position sensing signal at the determined position, which is processed by the signal conversion circuit. Control the power switch circuit to switch the winding current according to a certain logic relationship).
3. High speed permanent magnet brushless motor:
It consists of a stator core, a magnetic steel rotor, a sun gear, a deceleration clutch, and a hub shell.

A Hall sensor can be mounted on the motor cover for speed measurement.
Position sensors are available in magnetic, photoelectric and electromagnetic types.
A brushless DC motor using a magnetic sensitive position sensor, the magnetic sensing element (such as a Hall element, a magnetic sensitive diode, a magnetically sensitive diode, a magnetoresistor or an ASIC) is mounted on the stator assembly. To detect the change of the magnetic field generated when the permanent magnet and the rotor rotate. Multi-purpose electric vehicles are Hall elements.
A brushless DC motor using a photoelectric position sensor has a photoelectric sensor device arranged at a certain position on the stator assembly, and a light shielding plate is mounted on the rotor, and the light source is a light emitting diode or a small light bulb. When the rotor rotates, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency due to the action of the visor.
A brushless DC motor using an electromagnetic position sensor is provided with an electromagnetic sensor component (for example, a coupling transformer, a proximity switch, an LC resonance circuit, etc.) on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will cause the electromagnetic sensor. A high frequency modulated signal is generated (the amplitude of which varies with rotor position).
The operating voltage of the stator windings is provided by an electronic switching circuit controlled by the position sensor output.

Equipment classification

The drive motor for electric vehicles is different from conventional industrial motors. The drive motor of an electric vehicle usually requires frequent start/stop, acceleration/deceleration, high torque required for low speed or climbing, low torque required for high speed running, and large shift range. Industrial motors are usually optimized at rated operating points. Therefore, electric vehicle drive motors are unique and should be classified separately.
For the brushless motor, according to whether the motor has a position sensor, it is divided into a position sensor without brush.
Motor (7 photos)
Machine and sensorless brushless motor. For brushless motors without position sensor, the car must be lifted first. After the motor has a certain rotation speed, the controller can recognize the phase of the brushless motor, and then the controller can supply power to the motor. Since the position sensorless brushless motor cannot achieve zero speed start, it is used less on electric vehicles produced after 2000. For brushless motors used in the electric vehicle industry, position sensor brushless motors are commonly used. Rotating 180°, the coil does not move, the Hall element senses the S-pole magnetic field. At this time, P1 and R2 are turned off, and P2 and R1 are turned on. It can be seen that the current i’ flows from the positive electrode of the battery to the negative pole of the battery through R1, coil and P2. The direction of the current i’ at point A in the energized coil is directed to the direction of the terminal (the vector direction is opposite to the direction of the i’ vector), and the magnetic steel is subjected to the reaction force of the coil to generate a rotational torque in the counterclockwise direction. The number of magnetic steels for brushless motors for electric vehicles is relatively large. There are generally three sets of coils. Each set of coils has corresponding Hall elements (three phase coils have three Hall elements), so that the motor rotates more smoothly and efficiently. higher. When the magnetic steel rotates, the Hall element senses the change of the magnetic field direction and gives a corresponding control signal, and the brushless controller controls the conduction and the cut-off of the upper 3 and lower 3 power tubes according to the signal.

Product comparison

Comparison of brushed motor and brushless motor
The difference between the brushing motor and the brushless motor is that the brush motor is mechanically commutated by the carbon brush and the commutator, and the brushless motor is electronically commutated by the controller by the Hall element sensing signal.
Brushed motors and brushless motors have different energization principles and their internal structures are different. For the hub type motor, the output mode of the motor torque (whether it is decelerated by the gear reduction mechanism) is different, and the mechanical structure is also different.
1. The internal mechanical structure of common high speed brushed motors. The hub type motor is composed of a built-in high speed brush motor core, a reduction gear set, an overrunning clutch, a hub end cover and the like. The high speed brushed geared hub motor belongs to the inner rotor motor.
2. The internal mechanical structure of common low speed brushed motors. The hub type motor is composed of a carbon brush, a phase changer, a motor rotor, a motor stator, a motor shaft, a motor end cover, a bearing and the like. The low speed brushless gearless hub motor belongs to the outer rotor motor.
3. The internal mechanical structure of common high speed brushless motors. The hub type motor is composed of a built-in high speed brushless motor core, a planetary friction roller, an overload clutch, an output flange, an end cover, a hub shell and the like. The high speed brushless geared hub motor is an inner rotor motor.
4. The internal mechanical structure of common low-speed brushless motors. The hub type motor is composed of a motor rotor, a motor stator, a motor shaft, a motor end cover, a bearing and the like. The low speed brushless gearless hub motor belongs to the outer rotor motor.

Working principle

Motors are devices that convert electrical energy into mechanical energy. It uses a coiled coil (that is, a stator winding) to generate a rotating magnetic field and acts on the rotor squirrel-cage closed aluminum frame to form a magnetoelectric rotational torque. The electric motor is divided into a direct current motor and an alternating current motor according to the use of the power source. The electric motor in the electric power system is mostly an alternating current motor, and may be a synchronous motor or an asynchronous motor (the stator magnetic field speed of the motor and the rotational speed of the rotor are not kept at the synchronous speed). The motor is mainly composed of a stator and a rotor, and the direction of the force-carrying wire in the magnetic field is related to the direction of the current and the direction of the magnetic induction line (the direction of the magnetic field). The working principle of the motor is that the magnetic field acts on the current to force the motor to rotate.
basic introduction
An electric motor is a rotary electric machine that converts electrical energy into mechanical energy. It mainly consists of an electromagnet winding or distributed stator winding for generating a magnetic field and a rotating armature or rotor. Under the action of the rotating magnetic field of the stator winding, it has a current passing through the armature squirrel cage aluminum frame and is rotated by the action of the magnetic field. Some of these machines can be used as motors or as generators. It is a machine that converts electrical energy into mechanical energy. Usually, the work part of the motor is rotated. This type of motor is called a rotor motor. It is also called a linear motor.
basic structure
1. The structure of a three-phase asynchronous motor consisting of a stator, a rotor and other accessories
Electric vehicle controller
Electric vehicle controller
(1) Stator (still part)
1, the stator core
Function: A part of the magnetic circuit of the motor and the stator windings placed on it.
Structure: The stator core is generally formed by laminating and laminating a silicon steel sheet having an insulating layer on the surface of 0.35 to 0.5 mm thick, and a uniformly distributed groove is punched in the inner circle of the core for embedding the stator winding.
There are several types of stator core slots:
Semi-closed groove: The efficiency and power factor of the motor are higher, but the winding and insulation are more difficult. Generally used in small low voltage motors.
Semi-opening groove: It can be embedded with molded windings, and is generally used for large and medium-sized low-voltage motors. The so-called forming winding, that is, the winding, can be placed in the groove before being insulated.
Open type slot: used to embed the formed winding, the insulation method is convenient, mainly used in high voltage motors.
2, stator winding
Function: It is the circuit part of the motor, which is connected to three-phase alternating current to generate a rotating magnetic field.
Structure: It is made up of three identical windings with 120° electrical angles and the same arrangement of the team. The coils of these windings are respectively embedded in the slots of the stator according to certain rules.
The main insulation items of the stator windings are as follows: (to ensure reliable insulation between the conductive parts of the windings and the core and reliable insulation between the windings themselves).
(1) Insulation to ground: insulation between the stator winding and the stator core.
(2) Phase-to-phase insulation: insulation between stator windings of each phase.
(3) Turn-to-turn insulation: insulation between turns of each phase stator winding.
Wiring in the motor junction box:
There is a wiring board in the motor junction box. The six wire ends of the three-phase winding are arranged in two rows, and the three terminal blocks in the upper row are numbered 1 to 1 (U1), 2 (V1), and 3 from left to right. (W1), the three wiring posts in the lower row are numbered 6 (W2), 4 (U2), and 5 (V2) from left to right. The three-phase windings are connected in a star connection or a delta connection. All manufacturing and maintenance should be arranged according to this serial number.
3, the base
Function: Fix the stator core and the front and rear end caps to support the rotor, and play the role of protection and heat dissipation.
Construction: The base is usually cast iron, the large asynchronous motor base is usually welded with steel plate, and the base of the micro motor is made of cast aluminum. There is a heat dissipation rib on the outer surface of the closed motor to increase the heat dissipation area. The end caps of the protective motor have ventilation holes at both ends, so that the air inside and outside the motor can be directly convected to facilitate heat dissipation.
(2) Rotor (rotating part)
1. Rotor core of three-phase asynchronous motor:
Function: As part of the magnetic circuit of the motor and placing the rotor windings in the core slot.
Construction: The material used is the same as that of the stator. It is made of 0.5 mm thick silicon steel sheet and laminated. The outer surface of the silicon steel sheet is punched with evenly distributed holes for the rotor winding. The inner core of the silicon steel sheet that is behind the stator core is usually used to punch the rotor core. Generally, the rotor core of a small asynchronous motor is directly press-fitted on a rotating shaft, and the rotor core of a large and medium-sized asynchronous motor (with a rotor diameter of 300 to 400 mm or more) is pressed against the rotating shaft by means of a rotor bracket.
2. Rotor winding of three-phase asynchronous motor
Function: Cutting the rotating magnetic field of the stator generates induced electromotive force and current, and forms electromagnetic torque to rotate the motor.
Construction: divided into squirrel cage rotor and wound rotor.
(1) Squirrel-cage rotor: The rotor winding consists of a plurality of bars inserted into the rotor slots and two end rings of the ring. If the rotor core is removed, the entire winding is shaped like a squirrel cage, so it is called a cage winding. The small cage motor adopts a cast aluminum rotor winding, and is welded by a copper strip and a copper end ring for a motor of 100 KW or more.
(2) Wire-wound rotor: The wound rotor winding is similar to the stator winding, and is also a symmetrical three-phase winding, which is generally connected in a star shape, three outgoing heads are connected to the three collecting rings of the rotating shaft, and then passed through the brush. Connected to an external circuit.
Features: The structure is more complicated, so the application of the wound motor is not as extensive as the squirrel cage motor. However, through the collector ring and the brush, additional components such as resistors are inserted in the rotor winding circuit to improve the starting and braking performance and speed regulation performance of the asynchronous motor. Therefore, equipment that requires smooth speed regulation within a certain range, such as Cranes, elevators, air compressors, etc. are used above.
(3) Other accessories for phase asynchronous motors
1. End cap: support function.
2. Bearing: Connect the rotating part and the moving part.
3. Bearing end cover: protect the bearing.
4. Fan: Cool the motor.
Second, the DC motor adopts an octagonal full laminated structure, which not only has high space utilization, but also can withstand pulsating current and rapid load current change when powered by a static rectifier. DC motors generally do not have series-excited windings and are suitable for use in automatic control techniques that require forward and reverse rotation. It can also be made with series excitation winding according to user needs. The motor with a center height of 100 to 280 mm has no compensation winding, but the motor with a center height of 250 mm and 280 mm can be made with a compensation winding according to the specific conditions and needs. The motor with a center height of 315 to 450 mm has a compensation winding. The shape and technical requirements of the motor with a center height of 500-710mm are in line with the IEC international standard, and the mechanical dimensional tolerance of the motor conforms to the ISO international standard.
The working principle of DC motor:
In the figure, the coil is connected to the commutator piece, the commutator piece is fixed on the rotating shaft, rotates together with the motor shaft, and the commutating piece and the commutating piece and the rotating shaft are insulated from each other, and the whole structure thereof is called commutation Device. The brushes A and B are fixed in space.
The DC voltage is applied to the two brush ends of the motor, and the electric energy is introduced into the armature coil due to the action of the brush and the commutator, and the current in the same lower coil side is always one direction, which ensures the The direction of the electromagnetic force received by the lower coil side is constant, which ensures that the motor can continuously rotate to convert electrical energy into mechanical energy to drive the production machine. This is the working principle of the DC motor. Note: The current direction in each coil side is alternating.
2. Working principle of DC generator:
As shown in the figure, when the prime mover drags the armature to rotate counterclockwise, the coil side will cut the magnetic line to induce the potential, and the potential direction can be determined according to the right hand rule. Due to the continuous rotation of the armature, the coil sides ab and cd will alternately cut the magnetic lines of force under the N and S poles, and the direction of the induced electromotive force in each coil side and the entire coil is alternating, and the induced electromotive force in the coil is alternating. The electromotive force, but due to the action of the brush and the commutator, the current flowing through the load is a unidirectional direct current, which is generally pulsating.

Main characteristics

Brushless DC motors are widely used in electric vehicles because they have the following two advantages over conventional brushed DC motors.
(1) Long life, maintenance-free, and high reliability. In the brushed DC motor, the brush and the commutator wear faster because of the higher motor speed, and the brush needs to be replaced after about 1000 hours of work. In addition, the technical difficulty of the reduction gear box is relatively large, especially the lubrication problem of the transmission gear, which is a relatively large problem in the current brush scheme. Therefore, the brush motor has problems such as high noise, low efficiency, and easy failure. Therefore, the advantages of brushless DC motors are obvious.
(2) High efficiency and energy saving. In general, because brushless DC motors have no mechanical commutation friction loss and gearbox consumption, as well as speed control circuit losses, the efficiency is usually higher than 85%, but in view of the most cost-effective design in the actual design, to reduce material consumption. The general design is 76%. The efficiency of brushed DC motors is typically around 70% due to the consumption of gearboxes and overrunning clutches.

Method of operation

In the electric bicycle industry, the motor generally refers to the motor assembly, including the motor core and the speed reduction mechanism. The electric bicycles we talk about below all refer to the motor assembly.
First, the disassembly of the motor
Before disassembling the motor, first unplug the motor and the controller. At this time, record the one-to-one correspondence between the color of the motor lead and the color of the controller lead. Clean the operating area before opening the motor cover to prevent debris from being attracted to the magnetic steel inside the motor. Make the mark of the relative position of the end cap and the hub. Note: Be sure to loosen the screws in a diagonal order to avoid deformation of the motor casing. The radial clearance between the rotor and the stator of the motor is called the air gap (air gap), and the air gap of the motor is generally between 0.25 and 0.8 mm. After disassembling the motor to eliminate the motor failure, it must be assembled according to the original end cap mark, which can prevent the broom phenomenon after the secondary assembly.
Second, the lubrication of the internal gear of the motor
If the noise of the gear hub motor and the brushless gear hub motor starts to increase, or the gear in the motor is replaced, all the tooth surfaces of the gear should be coated with grease, generally using No. 3 grease or manufacturer-specified lubricating oil.
Electric vehicle motor
Electric vehicle motor
Third, the assembly of the motor
Before assembling the brush motor, please check the elasticity of the spring inside the brush holder, check whether the carbon brush and the brush holder are rubbed, check whether the carbon brush can reach the maximum stroke in the brush holder, and pay attention to the correct positioning of the carbon brush and the phase changer. In order to avoid bad carbon brushes or brush grips.
When installing the motor, first clean the impurities on the surface of the motor components, so as not to affect the normal operation of the motor, and the hub body must be fixed and strong, so as to avoid the components being impacted and damaged due to the strong attraction of the magnetic steel during installation. The detection of 36V is normal, the controller output is 5V, 12V is normal, and the motor resistance is normal. Connect the motor directly to the 36V battery and the motor is running normally.
Fourth, the wiring method
Since the commutation method is different, the brush motor and the brushless motor not only have different internal structures, but also have a great difference in the wiring method.
1. Wiring method for brush motor. Brushed motors generally have two positive and negative leads. Generally, the red line is the positive pole of the motor and the black line is the negative pole of the motor. If the positive and negative poles are exchanged, it will only reverse the motor and generally will not damage the motor.
2. Judgment of the phase angle of the brushless motor. The phase angle of the brushless motor is an abbreviation of the phase algebraic angle of the brushless motor, and refers to the angle at which the current direction of the coil inside the coil of the brushless motor changes in one energization period. Common phase algebra angles for brushless motors for electric vehicles are 120° and 60°.
Observe the phase position of the Hall component installation space to judge the phase angle of the brushless motor. The installation positions of the Hall components of the 120° and 60° phase angle motors are different.
Measuring the true value of the Hall to determine the phase angle of the brushless motor
Need to explain what is the magnetic pull angle of the brushless motor. The number of magnetic steels of a brushless motor is generally 12, 16 or 18, and the corresponding number of stator slots is 36 slots, 48 ​​slots or 54 slots. When the motor is at rest, the magnetic flux of the rotor magnet has the characteristic of walking along the direction of the reluctance. Therefore, the position of the rotor magnet is stopped just at the position of the salient pole of the stator slot. The magnet does not stop at the center of the stator slot, so the relative position of the rotor to the stator is only 36, 48 or 54 of these limited positions. Therefore, the minimum magnetic pull angle of a brushless motor is 360/36°, 360/48° or 360/54°.
The Hall element of the brushless motor has five leads, which are the common power supply positive electrode of the Hall element, the common power negative pole, the A phase Hall output, the B phase Hall output, and the C phase Hall output. We can use the five Hall leads of the brushless controller (60° or 120°) to connect the positive and negative power supplies of the brushless motor Hall element leads, and the lead wires of the three A, B and C phase sensors. Arbitrarily connected to the leads of the controller Hall signal leads. When the controller is powered on and the controller supplies power to the Hall element, the phase angle of the brushless motor can be detected. The method is as follows: use the multimeter’s +20V DC voltage block,
Electric vehicle motor
Electric vehicle motor
The black test lead ground wire and the red test pen measure the voltage of the three lead wires respectively, and record the high and low voltages of the three lead wires. Rotate the motor slightly, let the motor rotate through a minimum magnetic pull angle, measure and record the high and low voltages of the three leads again, and record the recording 6 times. We use 1 for high potential and 0 for low potential, then –
If it is a 60° brushless motor and continuously rotates 6 minimum magnetic pull angles, the measured Hall true signal should be: 100, 110, 111, 011, 001, 000. Adjust the pin order of the three Hall element leads so that the true value signal changes in strict accordance with the above truth value, so that the three phases A, B, and C of the 60° brushless motor are judged.
If it is a 120° brushless motor, continuously rotate 6 minimum magnetic pull angles, the measured Hall true signal should be changed according to the law of 100, 110, 010, 011, 001, 101, so that the lead element leads are energized. The phase sequence is judged.
If you want to quickly measure whether the brushless motor is 60° or 120°, use the multimeter’s +20V DC voltage block, and the black test lead ground wire, the red test pen to measure the voltage of the three leads, and the three wires have voltage or none. The voltage is determined to be a 60° motor, otherwise it is 120°.
3. Wiring method of brushless motor. There are 3 coil leads of the brushless motor and 5 of the Hall leads. These 8 leads must correspond to the corresponding leads of the controller, otherwise the motor cannot rotate normally.
Generally speaking, brushless motors with 60° and 120° phase angles need to be driven by the corresponding 60° and 120° phase angle brushless motor controllers. The controllers of the two phase angles cannot be directly interchanged. . There are two types of correct wiring for the 6-wire line connecting the 60° phase angle brushless motor to the 60° phase angle controller, one for forward rotation and one for reverse rotation.
Because for the brushless motor with 120° phase angle, by adjusting the phase sequence of the coil lead and the phase sequence of the Hall lead, there are 6 correct wirings for the 8 wires connected to the controller, and 3 of them are positive. Turn, the other three types of motor are reversed.
If the brushless motor is reversed, it indicates that the phase angle of the brushless controller and the brushless motor are matched. We can adjust the steering of the motor like this: exchange the brushless motor with the A and C of the Hall lead of the brushless controller. Wiring; at the same time, the brushless motor and the main phase line A, B of the brushless controller are exchanged.
Electric bicycles can be roughly divided into three types. 1, DC hub motor, that is, brush motor, two lead wires, external PWM controller. 2, AC hub motor, with and without Hall sensing, three leads or more, external inverter controller. 3, DC brushless hub motor, including electronic commutator, two lead wires. External PWM controller. Be sure to distinguish and not be confused.

Technical requirements

They have different special requirements in terms of load requirements, technical performance and working environment:
1. The electric vehicle drive motor needs 4-5 times overload to meet the requirements of short-term acceleration or climbing; industrial motors only require 2 times overload.
2. The maximum speed of electric vehicles is required to reach 4-5 times of the basic speed when cruising on the road, while industrial motors only need to reach constant power, which is twice the basic speed.
3, electric vehicle drive motor needs to be designed according to the driving style of the model and the driver, and the industrial motor only needs to be designed according to the typical working mode.
4, electric vehicle drive motor requires high power density (generally required to reach 1kg / kw) and good efficiency map (high efficiency in a wide range of speed and torque range), which can reduce vehicle weight To extend the driving range; industrial motors generally consider power density, efficiency and cost, and optimize efficiency near the rated operating point.
5. Electric vehicle drive motors require high controllability, high steady-state accuracy, and good dynamic performance; industrial motors have only one specific performance requirement.
6. The electric vehicle drive motor is installed on the motor vehicle with small space and working in harsh environments such as high temperature, bad weather and frequent vibration. Industrial motors usually work in a fixed position.

Common malfunctions

Common faults in brushless DC motors are usually checked from their three components. When the fault location is not known, the motor body should first be inspected, followed by the position sensor, and finally the drive control circuit. In the motor body, problems may occur: A, poor motor winding contact, disconnection or short circuit. Will cause the motor to not turn; the motor can start in some positions, but can not start in some positions; the motor runs unbalanced. B. The main magnetic pole of the motor is demagnetized, which makes the motor torque significantly smaller, and the no-load speed is high and the current is large. A common problem with position sensors is that Hall element damage, poor contact, and positional changes can cause the motor output torque to become small. In severe cases, the motor will not move or vibrate back and forth at a certain point. The most prone to failure in the drive control circuit is the power transistor, which is the damage of the power transistor due to long-term overload, overvoltage or short circuit. The above is a simple analysis of the common faults of the brushless motor. The problem will be various when the motor is actually running. The inspector should pay attention to the fact that when the situation is not accurately grasped, it is not possible to electrify at will, so as to avoid damage to other components of the motor.

Maintenance method

The fault of the motor has two major categories: mechanical fault and electrical fault. The mechanical fault is easy to find, and the electrical fault is analyzed and judged by measuring its voltage or current. The following describes the detection and elimination of common faults of the motor.
1, the motor’s no-load current is large
When the no-load current of the motor is greater than the limit data, it indicates that the motor has failed. The reason for the large no-load current of the motor is that the internal mechanical friction of the motor is large, the coil is partially short-circuited, and the magnetic steel is demagnetized. We continue to do the relevant test and inspection projects to further determine the cause of the failure or the location of the failure.
The no-load/load speed ratio of the motor is greater than 1.5. Turn on the power supply and turn the rotary handle to make the motor rotate at high speed and no load for more than 10s. After the motor speed is stabilized, measure the no-load maximum speed N1 of the motor at this time. Under the standard test conditions, when driving over 200m distance, start measuring the maximum load speed N2 of the motor. No-load/load ratio = N2÷N1.
When the no-load/load speed ratio of the motor is greater than 1.5, it indicates that the magnetic steel demagnetization of the motor has been quite severe. The whole set of magnetic steel inside the motor should be replaced. In the actual maintenance process of the electric vehicle, the whole motor is generally replaced.
2, the motor is hot
The direct cause of motor heating is caused by large current, motor current I, motor input electromotive force E1, induced electromotive force of motor rotation (also called back electromotive force) E2, and the relationship between motor coil resistance R is: I=( E1-E2) ÷R, I increases, indicating that R becomes smaller or E2 decreases. The smaller R is generally caused by the short circuit or open circuit of the coil. The decrease of E2 is generally caused by the demagnetization of the magnetic steel or the short circuit of the coil and the open circuit. In the maintenance practice of the entire vehicle of the electric vehicle, the method of handling the heating failure of the motor is generally to replace the motor.
3. There is mechanical collision or mechanical noise inside the motor during operation.
Regardless of high-speed motors or low-speed motors, mechanical collisions or discontinuous irregular mechanical noise should not occur during load operation. Different types of motors can be repaired using different methods.
4, the vehicle mileage is shortened, the motor is weak
The reason for the short mileage of the car and the lack of motor (commonly known as the motor is not strong) is more complicated. However, when we have eliminated the above four kinds of motor faults, in general, the fault of the vehicle’s continuous mileage is not caused by the motor. This is related to the attenuation of the battery capacity, the charger is not fully charged, and the controller parameters drift (PWM). The signal does not reach 100%) and so on.
5, brushless motor phase loss
The lack of phase of the brushless motor is generally caused by damage to the Hall element of the brushless motor. We can compare the resistance of the Hall element output lead to the Hall ground wire and the lead of the relative Hall power supply, and use the comparison method to determine which Hall element has failed.
In order to ensure the accuracy of the motor commutation position, it is generally recommended to replace all three Hall components at the same time. Before replacing the Hall element, it must be clear whether the motor’s phase algebra angle is 120° or 60°. Generally, the position of the three Hall elements of the 120° phase angle motor is parallel. In the case of a 60° phase angle motor, one of the three Hall elements is placed 180° in a flipped position. [2]

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