250W electric bicycle motor refers to the driving motor used in electric bicycles. According to the different use environments and frequencies, the form is also different. Different types of motors have different characteristics. A permanent magnet DC motor is widely used in electric bicycle. 250W electric bicycle motor can be divided into brush motor and brushless motor according to the power on the form of the motor; according to the mechanical structure of motor assembly, it can be generally divided into "gear" (motor speed is high, need to be decelerated by gear) and "gearless" (motor torque output without any deceleration).
250W electric bicycle motor is a kind of equipment that converts electric energy into mechanical energy. It uses the electrified coil (that is, the stator winding) to generate the rotating magnetic field and act on the squirrel cage closed aluminum frame of the rotor to form the magnetoelectric force rotating torque. The motor is divided into DC motor and AC motor according to the different power supply. Most of the motors in the power system are AC motors, which can be synchronous motor or asynchronous motor (motor stator magnetic field speed and rotor rotation speed do not keep synchronous speed). The motor is mainly composed of a stator and rotor. The direction of force movement of conducting wire in a magnetic field is related to the direction of current and magnetic induction line (magnetic field direction). The working principle of the motor is that the magnetic field acts on the current to make the motor rotate.
The driving motor used in 250W electric bicycle motor is different from the conventional industrial motor. The driving motor of the electric bicycle usually requires frequent start/stop, acceleration/deceleration, high torque at low speed or climbing, low torque at high speed, and wide speed range. Industrial motors are usually optimized at the rated operating point. Therefore, 250W electric bicycle motors are quite unique and should be classified into one category separately.
For brushless motor, according to whether the motor has a position sensor, it can be divided into position sensor brushless motor and position sensor free brushless motor. For the brushless motor without a position sensor, the vehicle foot must be pedaled up 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. As the sensorless brushless motor can not achieve zero speed start, it is less used in electric bicycles produced after 2000. A Brushless motor with a position sensor is widely used in the electric bicycle industry. Rotate 180 ° and the coil does not move. Hall element senses the S-pole magnetic field. At this time, P1 and R2 are cut off, P2 and R1 are connected. It can be seen that the current I 'flows from the positive electrode of the battery through R1, coil, and P2 to the negative pole of the battery. The current I 'direction of point a in the energized coil is the direction that points to the terminal (the vector direction is opposite to the I' vector direction). The magnetic steel receives the reaction force of the coil and produces the rotating torque in the counter-clockwise direction. The number of magnetic steel brushless motor for an electric bicycle is relatively large. There are generally three groups of coils. Each group of coils has corresponding Hall elements (three-phase coil has three Hall elements), so the motor can rotate more smoothly and efficiently. When the magnet rotates, the hall element senses the change of the magnetic field direction and gives the corresponding control signal. According to the signal, the brushless controller controls the conduction and cut-off of the upper and lower power tubes.