TAILIEUCHUNG - Handbook of Small Electric Motors Episode 3

Tham khảo tài liệu 'handbook of small electric motors episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MATERIALS FIGURE Core loss at 200 Hz. dc applications the designer has the choice of a number of material systems each with unique properties that can be customized to meet specific part requirements. Care must be taken in the manufacture of the sintered P M parts to minimize the carbon and nitrogen pickup. By varying the alloying sintered density and processing the resulting magnetic properties cover a broad range of applications. For ac applications the P M industry has developed two families of powders that can be utilized in alternating magnetic fields. The choice between the iron powder-polymer composites and a powder that can be given a low-temperature annealing is based on the part function and ultimate part requirements. MAGNETIC TEST METHODS The characteristics of the magnetic core materials discussed in this chapter must be determined by certain specified procedures which are usually in accordance with the standard test methods of the ASTM. The data obtained from such measurements can be used in a comparison of the electrical and magnetic properties and as a guide in the selection of the best material for a particular design. The test methods utilized can be classified in two general groups those using direct current and those using alternating current as a source of power. Direct-Current Tests All direct-current test data are obtained by ballistic test methods. Ring samples or an appropriate test sample in one of several different permeameters were used with the basic circuit illustrated in Fig. or in a modification of this circuit. Section courtesy of Allegheny-Teledyne. CHAPTER TWO FIGURE Basic circuit diagram for demagnetic testing. For a more detailed discussion of this circuit and its adaptation to various test methods see ASTM A-34 on standard methods of test for normal induction and hysteresis of magnetic materials. The test methods described by ASTM cover most of the generally accepted test methods likely to be

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