Change of wholesale 110v dc motor in Electric Vehicles
The change direction problem is one of the main problems affecting the quality of DC motor. This paper introduces how to evaluate the index of redirection qualification; This paper discusses the causes of the impact of the change direction including electromagnetic, mechanical, electrochemical and other aspects; The methods and measures to improve the change direction are put forward: first, the position of the brush must be adjusted, the second is to pay attention to the quality of the commutator, the third is to pay attention to the choice of the brush, the fourth is to optimize the size of the brush box and the pressure of the spring, and the fifth is the brush. The grinding is very important. Finally, a rigorous and accurate life test is required.
First, the reasons why the change of direction is affected:
Why does the DC motor produce sparks in the process of changing direction? According to theoretical and practical analysis, there are many reasons for the impact of the change direction, such as electromagnetic, mechanical, electrochemical, and so on, and they interact with each other and are very complex. It is not ready to make too much analysis in theory. It is only for the DC motor used in electric bicycles to make some analysis of the problems that should be noticed in the production of changing direction. It may play a certain guiding role in production.
1, electromagnetic reasons:
At the time of redirection, the reactance potential and the redirection potential will be generated in the redirection element. The sum of these potentials is generally greater than zero, and the delayed redirection is called. When the redirection is changed, when the redirection edge leaves one redirection piece and turns to another adjacent redirection piece, the redirection current is not zero, and electromagnetic energy is stored in the redirection element. When the previous redirection piece leaves the brush, The redirection loop is suddenly cut off, and the electromagnetic energy in the redirection element is only released through the air, resulting in sparks.
2, mechanical reasons:
For the production, due to mechanical reasons, leading to bad change is an important aspect. There are many mechanical reasons, such as the flatness of the surface of the planar commutator, the roughness, and the vertical degree of the surface of the commutator and the axis of the motor during assembly; Insulation protrudes between commutators or commutators; The contact surface of the brush is not grinding well, and there is only local contact between the brush and the commutator surface; The spring pressure on the brush is not suitable; The brush is too loose or too tight in the brush box; The distance between the brush rods is not equal, so that the redirection elements short-circuited by some brushes are not on the geometric center line; The surface of the commutator is unclean and so on.
3, electrochemical reasons:
In a functioning motor, the surface of the commutator produces a very thin layer of copper oxide thin film. The practice shows that the existence of cuprous oxide thin film is a necessary condition for the motor to change direction well. This is because the cuprous oxide thin film itself not only has a high resistance, but also its surface is often adsorbed with thin layers of water, oxygen and graphite powder, which has a good lubrication effect and is conducive to reducing the wear of the brush and the changer.
