Commutation characteristics and brush wear of DC motor at high rotation speed

Many small-size DC commutator motors are still widely used in automobiles and other applications. In recent years, DC motors have been driven at high speed to realize small size and high-power. However, as is well-known, the commutation becomes difficult at higher speed and brush wear/erosion increases due to the commutation arc. Therefore, it is important to understand how the motor speed influences commutation phenomena, including arc duration and residual current, so the correct motor can be selected for the particular application to achieve the required reliability. In this paper as the rotation speed is changed from 1000 to 5000min−1, the influence of the speed on commutation characteristics is investigated, such as effective commutation period, arc duration and others. In addition, it is also examined how the rotation speed affects brush wear/erosion. Consequently the followings can be made clear. The effective commutation period decreases in inverse proportion to the rotation speed, while the arc duration and residual current are almost constant, around 42μsec and 0.55A respectively up to 3000min−1. When the rotation speed increased to 3000 and 5000min−1, brush wear/erosion is found to increase rapidly. This indicates that as arc erosion increases the mechanical wear also becomes larger due to the effect of arc discharge. Based on experimental results, a model including the effect of the rotation speed is proposed for brush wear/erosion.