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DC Machines
Published in Jacek F. Gieras, Electrical Machines, 2016
The armature coils are interconnected through the commutator, which consists of a number of insulated copper segments (Fig. 4.7). The commutator is located on the same shaft as the armature (rotor) and rotates together with the armature winding. The armature (rotor) core must be laminated to reduce the core losses that may arise due to the flow of AC current. In DC motors the commutator serves as a mechanical inverter. In DC generators, the commutator serves as a mechanical rectifier. Current is fed to the commutator with the aid of brushes, often made of carbon or graphite (Fig. 4.8). The brushes are held in brush holders (Fig. 4.9) and they must be free to move radially in order to maintain contact with the commutator as they wear away. The current is conducted from the brush to the brush stud by means of a brush pigtail. The brush-commutator mechanism is shown in Fig. 4.10.
A power generation roadbed based on direct current triboelectric nanogenerators for human kinetic energy harvesting
Published in Journal of the Chinese Institute of Engineers, 2023
Baichuan Shan, Changxin Liu, Nanxi Chen, Jianhao Liu, Hao Sui, Huaan Li, Guangyi Xing, Runhe Chen
As shown in Figure 1a, Qiao et al. (2021) proposed a rolling bi-directional DC friction nanogenerator with its mechanical rectifier, which directly outputs DC signals through the action of rolling brushes and commutator. Liu et al. (2019) proposed a sliding air breakdown DC friction nanogenerator with a simpler structure. With the friction electrode rubbing against the friction layer in constant contact, there is a continuous output of a pulsed DC signal as shown in Figure 1b. After this, a new structure rotating air breakdown DC friction nanogenerator was proposed, as shown in Figure 1c (Liu et al. 2020). The power generation principle of this structure DC friction nanogenerator is the same as that of the sliding air breakdown DC friction nanogenerator mentioned above. It can directly light up 83 small LED lights and directly drive electronic watches and commercial electronic devices calculators under the driving speed of 500 r/min. As the prototype of air breakdown DC friction nanogenerator was designed, subsequent research focus on the effects of environmental conditions on its power generation performance. Specifically, investigations were conducted on the influence of environmental pressure and humidity (Liu et al. 2020). Based on the research of other researchers, a new rotating structure is utilized in this paper, which makes the efficiency of power generation has a certain improvement effect and provides an effective technical solution for the energy problem in intelligent cities.