tailieunhanh - Fundamentals of Electrical Drivess - Chapter 2

Chapter 2 SIMPLE ELECTRO-MAGNETIC CIRCUITS Các thành phần đơn giản sử dụng tương tác điện từ là cuộn dây. Cuộn dây là một thành phần bộ đệm lưu trữ năng lượng dưới hình thức từ. Các cuộn dây Aircored thường được sử dụng (cho ví dụ trong các bộ lọc loa), nhưng các cuộn dây với một lõi (có thể gapped) từ nguyên liệu là phổ biến hơn bởi vì điện cảm gia tăng (hoặc giảm kích thước), mà đi kèm với chi phí giảm sức mạnh của lĩnh vực tối đa và tăng phi tuyến tính. Trong chương này, chúng. | Chapter 2 SIMPLE ELECTRO MAGNETIC CIRCUITS Introduction The simplest component utilising electro-magnetic interaction is the coil. The coil is a buffer component which stores energy in magnetic form. Aircored coils are frequently used for example in loudspeaker biters but coils with a core of possibly gapped- magnetic material are more common because of their increased inductance or reduced size which comes at the cost of reduced maximurnf l sfini thn tlinhmased non-linearity. In this chapter we will develop a generic model of a coil with linear and nonlinear self of coil resistance considered. The use of phasorsisintcoduced io this chhpCeras a meansec norifynmulation of such circuits wlacncoaneoted tonsinoeoidalsource. Linear ioductance The physical rep pf 00 coil . isgiocnta flgure . The figure shows a eoilwrhirt. lurns which iswn pm d onndrrhiK iOally shopel non-gapped magnetin ooseorthonorsrsectienoiaseo es unp h tln hlợoc the material is giver aipaadiOe ovesttge fluona Seegthis equnlioii0iAnalog to equations the magnetic reluctance of the circuit is Rm and the inductance is L n2ụ. Am Ỉm n2 Rm. The relation between the magnetic flux and the current in the coil is described by the expression 1C L i With Faraday s law nn 30 FUNDAMENTALS OF ELECTRICAL DRIVES equation can be rewritten to the more familiar differential form of the coil s voltage terminal equation u L - at Equation can be integrated on both sides and rewritten as the general equation 1 ipf ee-ỉ-i uự dt J oo The whole integrated history of the inductor voltage is reflected by the inductor current so equation can be expressed in a more practical form starting at t 0 with initial condition O aciording 1 i-t r ỊữU t dt r tíS This integral form can bedevolopel further AiO Si A ij it0 ý t - V 0 J ust dt introducing the com WPimremCTtaiflrn-linka A fe t - o which is fundamental to the control of electrical