0195136047.pdf

534 ELECTROMECHANICS Solution (a) A change in the energy stored in the electromagnetic fielddWmis equal to the sum of the increm ...

12.4 FORCES AND TORQUES IN MAGNETIC-FIELD SYSTEMS 535 |f|= φ^2 2 dR(x) dx = 1 2 ( Ni R ) 2 dR dx = i^2 2 N^2 R^2 dR dx = 1. 52 2 ...

536 ELECTROMECHANICS Solution (a) The force in the air gap can be expressed by f=− 1 2 φ^2 dR dx (See Example 12.4.2.) The gap r ...

12.4 FORCES AND TORQUES IN MAGNETIC-FIELD SYSTEMS 537 EXAMPLE 12.4.4 A relay is essentially an electromechanical switch that ope ...

538 ELECTROMECHANICS Forx= 0 .25 cm and|f|=100 N, i^2 = 100 ( 0. 25 × 10 − 2 )^2 2. 5 π× 10 −^4 = 2. 5 π = 0. 795 or i= 0 .89 A ...

12.5 BASIC ASPECTS OF ELECTROMECHANICAL ENERGY CONVERTERS 539 since the average value of the square of a sine wave is one-half o ...

540 ELECTROMECHANICS Besides the stator and rotor iron-core losses,friction and windagelosses (which are generally functions of ...

12.7 PRACTICAL APPLICATION: A CASE STUDY 541 Basic principles of electromechanical energy conversion, including induction, inte ...

542 ELECTROMECHANICS Data gathering with various sensors and data reduction have become much easier, automatic, and quite sophis ...

PROBLEMS 543 y x B a a a' a' θm ωm ωm y z l w B Axis of rotation Figure P12.1.3Rotating conducting loop. (c) Calculate the avera ...

544 ELECTROMECHANICS Cylindrical cast-steel shell 1000-turn coil Cylindrical plunger 12.5 cm 10 cm 1.25 cm g 1.25 cm 10 cm 5 cm ...

PROBLEMS 545 ωm θm Stator magnetic axis Rotor magnetic axis Figure P12.2.1Rotating machine with uniform air gap. (iv) Obtain the ...

546 ELECTROMECHANICS induced voltage, given that the number of parallel paths is equal to the number of poles for lap windings. ...

PROBLEMS 547 N turns i Cylindrical plunger Spring Nonmagnetic cylindrical sleeve t x t 0 x 0 : position of plunger when spring i ...

548 ELECTROMECHANICS l b Air gap N-turn coil Nonmagnetic sleeve g a c μ = ∞ μ = ∞ Cylindrical core Plunger Mean radius of sleeve ...

PROBLEMS 549 Ns turns vs is − + ωm Rotor axis Rotor Stator pole axis Stator (d-axis or direct axis) Interpole axis (q-axis or qu ...

550 ELECTROMECHANICS i 1 L 11 L 22 θ Movable coil i^2 Fixed coil Figure P12.4.11 Stator b-phase axis θ ia ib if − + Stator a-pha ...

PROBLEMS 551 torque under these conditions and describe its nature. (b) Compare the torque with that of Problem 12.4.12(b). (c) ...

552 ELECTROMECHANICS (a) Obtain expressions for self and mutual in- ductances, assuming infinite permeability for the magnetic c ...

13 Rotating Machines 13.1 Elementary Concepts of Rotating Machines 13.2 Induction Machines 13.3 Synchronous Machines 13.4 Direct ...