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This comprehensive overview of DC machines covers their introduction, advantages, adjustable speed capabilities, and how they develop rated torque across all speeds. It discusses the benefits of DC motors, including higher torque than equivalent AC machines. The text delves into practical applications involving robotics, automotive, and railroads. The focus is on the fundamental concepts of 2-pole DC motors, commutation, and induced voltage, making it essential for students of electrical engineering and professionals interested in motor technology.
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Introduction to DC Machines • Advantages • Adjustable speed • Develop rated torque at all speeds • Higher torque than an equivalent AC machine • Uses • Robots • Automotive • Railroads ECE 441
Elementary 2-pole DC motor Poles created by DC current in the field winding or by a permanent magnet ECE 441
Flux through the “window” of a 1-turn armature coil as a function of position ECE 441
Flux Distribution and Induced Voltage The induced voltage is AC ECE 441
Average Value of one-half cycle ECE 441
Rectify the other half-cycle Ea ECE 441
Express in r/min ECE 441
Commutation / Mechanical Rectification • “Neutral” position • Coil shorted by the brushes • No armature voltage generated – coil sides not cutting any flux • No current ECE 441
Commutation (continued) • Brushes contact the armature conductor • CCW rotation • Coils sides cut flux • Current in A as shown • Current in B as shown ECE 441
Commutation (continued) • “Neutral” position • As before, coil shorted by the brushes • No armature voltage generated – coil sides not cutting any flux • No current ECE 441
Commutation (continued) • Brushes contact the armature conductor • CCW rotation • Coils sides cut flux • Current in B as shown • Current in A as shown • Currents are in the same direction as before! ECE 441