tailieunhanh - Handbook of Small Electric Motors Episode 5

Tham khảo tài liệu 'handbook of small electric motors episode 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 4 DIRECT-CURRENT MOTORS Chapter Contributors Andrew E. Miller Earl F. Richards Alan W. Yeadon William H. Yeadon This chapter covers methods of calculating performance for direct-current dc mechanically commutated motors. Section discusses the electromagnetic circuit for dc motors and series ac motors. Sections and establish some common geometry and symbols and discuss commutation for dc motors. Section presents permanent-magnet direct-current PMDC calculation methods. Section presents series dc and universal ac dc performance calculations. Sections and discuss methods for calculating the performance of shunt- and compound-connected dc motors. Finally Secs. and discuss dc motor windings and automatic armature winding. THEORY OF DC MOTORS DC Series Motors A series motor operating on direct current has characteristics similar to those when it is operated on ac current at power-system frequencies. However it is best to describe dc and ac operation separately so that comparisons can be made. The general equivalent electrical circuit of the series dc motor and its physical construction is shown in Figs. and motor consists of a stator having a concentrated field winding Fig. connected in series by way of a commutator to a Section contributed by Earl F. Richards. CHAPTER FOUR wound armature Fig. . One of the first things to be considered in the operation of the motor are the motor and generator action which exist simultaneously in the armature circuit of the motor. These two principles are 1 the instantaneous electromotive force emf which is induced in the armature conductors when moving with a velocity v within a magnetic field and 2 the force produced on the conductors as the result of carrying an electric current in this same magnetic field. Steady-Slate Model FIGURE Series motor diagram ra armature resistance measured at brushes r main field resistance and v applied .

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