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DC Machines
Published in Zeki Uğurata Kocabiyikoğlu, Electromechanical Energy Conversion, 2020
Figure 6.12 shows a simple permanent magnet DC machine with a split ring structure. Each end of the coil is fixed to one half of a ring. For motor operation, a DC voltage is applied to the coil through the two brushes which ride on these half rings. The action of changing the connections between the brushes and the coil sides is called commutation. Commutation is necessary in order to develop a torque which is always equal and in opposite directions on the two sides of the coil so that rotation of the coil can take place. Through this action, the same polarity of voltage is always applied to the coil side on the right (next to the south pole) and on the left (next to the north pole). This way we obtain a torque which rotates the coil always in the same direction (clockwise in our example).
Electric Motors
Published in Ranjan Vepa, Electric Aircraft Dynamics, 2020
The inverter switching sequence results in the commutation of the current and is determined by sensing the rotor position. The sensing of the rotor position is done by a distribution of Hall-effect sensors. The commutation is achieved by a set of switching transistors that are operated sequentially to switch on and switch off the current in each phase, in such a way as to keep the current flow in the appropriate direction necessary to maintain the rotor motion. The current feedback in each phase is a trapezoidal pulse with the linear portion of the pulse overlapping in two of the three phases. This permits a smooth transition from one phase to the next. A single cycle of the trapezoidal periodic pulse spans 360°: it starts at zero, is flat with maximum and minimum magnitude over the 60°–120° and 240°–300° regions respectively, ends at zero and is linearly varying everywhere else. Although the principal component of the torque is sinusoidal, there is a higher harmonic torque ripple. Ignoring the torque ripple, one can show that the rotor is generally maintained at constant speed.
Electrical, Electronic, and Electromechanical Systems
Published in Ramin S. Esfandiari, Bei Lu, Modeling and Analysis of Dynamic Systems, 2018
In a variety of electromechanical systems, electrical and mechanical subsystems are coupled by a magnetic field. Figure 6.42 shows a DC motor, which consists of basic elements (including the stator, the rotor, the armature, and the commutator). The stator provides a magnetic field across the rotor. The current is conducted to coils attached to the rotor via brushes, and the rotor is free to rotate. The combined unit of coils attached to the rotor is called the armature. The brushes are in contact with the rotating commutator, which causes the current to always be in the proper conductor windings, so as to produce a torque and keep it in the proper direction. The magnetic coupling relations between the electrical and mechanical subsystems in a DC motor can be derived using fundamental electromagnetic laws in introductory physics textbooks [4].
Designing MPC algorithms for velocity control of brushed DC motor and verification with SIL tests
Published in Automatika, 2023
Brushed DC (BDC) motors have been widely used in various fields, such as pumps, air fans, automotive window mechanisms, and windshield wipers. With the development of technology, it has found intensive use in high-technology areas such as robotics, drones, and missile actuators [1,2]. An essential step in controlling the BDC motor is commutation. The commutation process in BDC motors is carried out by the contact of a brush with a sliding mechanical surface. This mechanical method is reliable and able to withstand high voltage and current. In addition to these advantages, sparks or arcs may occur in the mechanical commutator and thus create a risky situation [3].
Analysis of bridge type and bridgeless cuk converter fed motor drives for improved power quality
Published in International Journal of Electronics, 2023
Red denotes positive and black denotes negative polarity. The rotation happens by the principle : ‘Opposite polarities attract and Identical polarities repel’. The commutation is done in order that rotor rotation is continuous in one direction. The same method goes on for the remaining three states of rotation also