Permanent magnet motors are divided into two categories: brush motors and brushless motors. Brushed motors and brushless motors. Brushes and brushless motors refer to continuous rotation of DC motors with or without brushes. They rely on the magnetic field of the rotor and the magnetic field of the stator to repel and attract each other of the same sex. The current in the wire package must be converted in the appropriate machine, otherwise it will be sucked to death. The brush motor is automatically completed by the cooperation of the commutator (scientific name is commutator) and the brush, and the commutator and the brush are installed inside the motor. To
Generally, the brushes of brush motors should be replaced after they are worn out for about 2000 hours. Ordinary hub motors and column motors (also called mid-mounted motors) need to be replaced by professional maintenance personnel, while ordinary users of series motors can replace them by themselves. The wear of the brush is also related to the current size and the silver content of the brush. The series-excited motor used in freight three-wheelers has a large current, and the life span is less than 2000 hours. It must be replaced within a few months. The price of carbon brushes varies greatly in terms of silver content. The brushed motor has only two external connections. The permanent magnet brushed motor can change the direction of rotation by swapping the connections; the series motor has no permanent magnets, and both the rotor and the stator are windings. The stator magnetic field is also called the exciting magnetic field, and each winding is independent Yes, when used in series, it is called a series-excited motor. Although the series motor also has two external connections, it is different from the permanent magnet brush motor that can change the direction of rotation by swapping the connection, but exchanges the rotor winding (a pair of wires) or the stator winding (a pair of wires). That's it. As the name implies, the brushless motor has no brushes inside the motor. The winding current conversion is carried out by an external brushless speed controller (hereinafter referred to as the brushless controller). However, the brushless motor must provide the rotor position for the brushless controller. Commonly used brushless motors have 8 leads, of which three are thick yellow, thick green, and thick blue, which are winding leads, and the remaining 5 thin wires are rotor position sensor leads. Thin red is generally positive 5V, thin black is 5V negative and signal common terminal, thin yellow, thin green, and thin blue are the 3 rotor position signal leads. Brushless controllers rely on the signals they provide to change the direction of the winding current. There are two types of brushless motors for electric vehicles, 60 degrees and 120 degrees, which cannot be seen from the outside. The brushless controller also has 60 degrees and 120 degrees, and the motor and the controller must be matched. There are 36 ways of connecting the 8 wires between the brushless motor and the brushless controller: only two of the 60 degrees are correct, one is forward and the other is reverse; the 120 degrees is positive, and there are six. 3 types of forward rotation and 3 types of reverse rotation. The results of mismatched degrees or incorrect wiring are: no rotation, weak rotation, vibration, large current under light load, etc. Seriously, it may damage the controller or the Hall rotor position sensor inside the motor.
Simple comparison of brushed and brushless motors
Although the advantages of brushed motors are troublesome, the technology is mature, the accessories are easy to buy, and the matching brushed speed controller (hereinafter referred to as the brush controller) is cheap; the disadvantage is that after the brush is severely worn, the motor cover needs to be opened and replaced. The brushless motor does not have the problem of opening the cover to replace the brush. It is theoretically more power-saving than the brushed motor, and it is subjectively powerful. The disadvantage is that the matching brushless controller is much more expensive than the brush and the failure rate is also higher. Since the second half of last year, the price of brushless controllers has dropped significantly and the quality has improved. Therefore, there are more and more electric bicycles and electric motorcycles using brushless motors, which have the potential to replace the dominant position of brush motors. However, maintenance problems plague most maintenance workers. This is because most of this industry is diverted from repairing bicycles and repairing motorcycles, and little is known about brushless motors and brushless controllers. For example, the simplest way to change the steering problem of a brushless motor is to exchange the first and third phase connections of the rotor position sensor at the same time. However, most maintenance workers do not understand how to determine the 3 positions of the rotor position sensor and the wire package winding. Of course, there is an objective reason here, that is, although the three wires of the rotor position sensor and the coil winding are all yellow, green, and blue, different manufacturers and different batches may be different, the first phase, second phase, and first phase. The three-phase is not constant, and the same is true for the brushless controller, which causes difficulty in maintenance, that is, the corresponding color wiring may not rotate correctly. To
Common electric bicycle motors are called hub motors, some can be installed with spokes and rims, and some can be integrated with the motor and rim without additional spokes. The latter is also called an integrated hub motor in the industry. The former has good impact resistance and has good impact on the motor. favorable. Generally, a motor speed above 3000 rpm is called a high-speed motor, and a motor speed below 1000 rpm is a low-speed motor. At present, the brushless gearless hub motor can achieve 600 rpm or less. Home requires the speed of electric bicycles to be less than 20 km/h, which is about 200 rpm for a 24 (inch) bicycle. You can use a small gear with a large gear to reduce speed. The gear ratio of the large and small gears is called the reduction ratio. The reduction ratio is large, the torque is also large, and the climbing is strong. The gear can be installed inside the motor or outside the motor. The brushed and toothed, brushless and geared hub motors are installed inside.
The three freight wheels introduced above are two-stage reduction. The first stage is inside the series motor, and the front protrusion is a planetary gear reduction mechanism. The planetary gear is nylon, and the second stage is outside the motor. The motor output is a small The gear is transmitted to the rear axle of the tricycle through a chain, and the rear axle is equipped with a large gear. Although the reduction ratio of the worm gear is large, the energy transmission efficiency is low. Spur gears are cheap but noisy; helical gears or "herringbone" gears are less noisy and costly. Nylon gears have a shorter lifespan than metal gears, but they are less noisy and cheaper. Theory and practice have proved: 1. The above-mentioned chain transmission and deceleration have low noise, high efficiency, easy to buy parts and easy replacement. 2. The motor is installed at the rear of the shaft, so it is not easy to lose the chain when moving forward.
Generally speaking, there are brush and toothless, brushless and toothless, brushed and toothed, and brushless and toothed wheel hub motors with gears and no gears inside. For motors with the same power, geared motors are stronger in starting and climbing than those without gears. They are suitable for sloped road conditions, and high-speed motors are more efficient. However, this type of motor has a low life span, and it is difficult to buy accessories and high maintenance costs.、