Learn more about electric bicycle motors

Definition of electric bicycle motor 

The motor has different forms according to its use environment and frequency. Different types of motors have different characteristics. At present, permanent magnet DC motors are widely used in electric bicycles. The so-called permanent magnet motor means that the motor coils are excited by permanent magnets, but not by coils. In this way, the electric energy consumed when the excitation coil works is saved, and the electromechanical conversion efficiency of the motor is improved, which can reduce the driving current and prolong the driving mileage for the electric vehicle using the limited energy on board. 

Electric bicycle motors can be divided into brush motors and brushless motors according to the power-on form of motors. (At present, except that the motors of electric wheelchairs are brush motors, all others are brushless motors). 

According to the mechanical structure of the motor assembly, it is generally divided into two categories: "toothed" (the motor has high speed and needs to be decelerated by gears) and "toothless" (the torque output of the motor does not undergo any deceleration). 

According to the presence or absence of Hall components, there are Hall motors and Hall-free motors. 

According to installation position: it is divided into hub motor and mid drive motor.

Brushless gear motor

Geared motor is also called deceleration motor or high-speed motor. The stator speed can reach about 1200RPM, and the final motor speed is about 280RPM through gear reduction (for example, the speed ratio is 1:4.4).

Because of the cost problem, most plastic gears are used, so their service life is limited. After a long time, the teeth of gears will be polished. If they are metal gears, there is no such problem, but the cost increases and the noise is slightly higher. At present, all our motors are nylon gear.

Advantages: small size, light weight, large torque, small running current and power saving. The motor has low noise.

Disadvantages: Low power and slow speed.

Gearless motor/DC motor

Gearless motor is also called low-speed motor. Simple structure, mainly composed of stator, hub and end cover. Without gear reduction, the speed of stator is directly output. The general rotating speed is 200-400RPM.

Advantages: High torque, high speed and high power. Because there is no gear system, the damage rate of smaller motor is low.

Disadvantages: large size, heavy weight, slightly larger running current and power consumption

Hall motor and Hall-free motor

Hall motor: there are three position Hall sensors in the motor. There are 8 motor outgoing lines, which are composed of 3 phase lines +3 Hall signal lines+2 positive and negative lines of Hall power supply. Since 2013, the speed sensor has been built inside the motor, so the outlet of Hall motor is 9 cores.

Hall-free motor: there are only three phase wires in the motor outlet. In case of in-band speed measurement sensing, the outgoing lines are 6 (3 phase lines +1 speed measurement Hall signal line +2 Hall power supply positive and negative poles).

Note: Hall motors must be matched with Hall controllers. Hall-free motors must be matched with Hall-free controllers. At present, there are also dual-mode controllers, which can be matched with or without Hall motors.

Working principle of Hall motor

Hall's signal line transmits the position of magnetic steel in the motor relative to the coil. According to the signals of the three Hall's, the controller can know how to supply power to the motor coil at this time (different Hall signals should supply the motor coil with current in the corresponding direction), that is to say, Hall states are different, and the current direction of the coil is different.

Hall signal is transmitted to the controller, which supplies power to the motor coil through thick line (phase line), the motor rotates, the magnet steel and the coil (exactly the coil wrapped around the stator) rotate, Hall induces a new position signal, the thick line of the controller supplies power to the motor coil to change the current direction again, and the motor continues to rotate (when the position of the coil and magnet steel changes, the coil must change the current direction correspondingly, so that the motor can continue to move in one direction, otherwise the motor will

Hall-free motor must pedal the vehicle first, and then the controller can recognize the phase of the motor after the motor has a certain rotation speed, and then the controller can supply power to the motor. This is called non-zero startup. Simply and popularly speaking, you need to step on your feet before you can accelerate with the handle.

On the contrary, if there is a Hall motor, the motor can be started up directly with the rotating handle, and it starts at zero.

Advantages of Hall-free motors: 

1. Longer service life and reliability, because no Hall can be damaged; 

2. The cost is low because Hall is not used

3. The manufacturing is simpler, without welding Hall;

Disadvantages of Hall-free motor:

1. The starting is not smooth, because there is no Hall to detect the rotor position, so the driving part needs to do zero-point current detection, which causes the motor to vibrate or even fail to start when starting;

2. It is not suitable for large load or large load change.

Advantages of hall motor:

1. Hall sensor is installed inside, which can detect the position of rotor and start smoothly;

2. The motor can start at zero speed thanks to Hall sensor;

Disadvantages of Hall motor:

1. The price is higher than that without Hall;

2. The structure is more complicated than that without Hall.

So do you have a new understanding about the electric bicycle motor now? If you have any questions, please discuss them with us.