【正文】 . The generated voltage as observed from the brushes and is the sum of the rectified voltages of all the coils in series between brushes and is shown by the rippling line labeled ae in figure. With a dozen or so mutator segments per pole, the ripple bees very small and the average generated voltage observed from the brushes equals the sum of the average values of the rectified coil 5 voltages. The rectified voltage ae between brushes, Known also as the speed voltage, is 2 aa d m a d mPCeKm ? ? ? ???? （ 14） where aK is the design constant. The rectified voltage of a distributed winding has the same average value as that of a concentrated coil. The difference is that the ripple is greatly reduced. From the above equations, with all variable expressed in SI units, a a mei T?? （ 15） This equation simply says that the instantaneous power associated with the speed voltage equals the instantaneous mechanical power with the magic torque. The direction of power flow being determined by whether the machine is acting as a motor or generator. The directaxis airgap flux is produced by the bined . ffNi? of the field windings. The . Characteristic being the magization curve for the particular iron geometry of the machine. In the magization curve, it is assumed that the armature –. Wave is perpendicular to the field axis. It will be necessary to reexamine this assumption later in this chapter, where the effects of saturation are investigated more thoroughly. Because the armature . is proportional to flux times speed, it is usually more convenient to express the magization curve in terms of the armature . 0ae at a constant speed 0m?. The voltage ae for a given flux at any other speed m? is proportional to the speed, . 00maamee??? （ 16） There is the magization curve with only one field winding excited. This curve can easily be obtained by test methods, no knowledge of any design details being required. Over a fairly wide range of excitation the reluctance of the iron is negligible 6 pared with that of the air gap. In this region the flux is linearly proportional to the total . of the field windings, the constant of proportionality being the directaxis airgap permeance. The outstanding advantages of . machines arise from the wide variety of operating characteristics that can be obtained by selection of the method of excitation of the field windings. The field windings may be separately excited from an external . source, or they may be selfexcited。 mutating poles (poses) and winding。s main current. The rotor core is built of ～ 1mm siliconalloy sheets. The sheets are insulated from one another by a thin film of varnish or by an oxide coating. Both some ～ thick. The purpose is to ensure a reduction of the eddy currents that arise in the core when it rotates inside the magic field. These currents cause energy losses that turn into heat. In solid cores, these losses could bee very high, reducing machine efficiency and producing intense heating. The rotor core consists of a few packets of metal sheet. Redial or axial cooling ducts (8～ 10mm inside) are inserted between the packets to give better cooling. Pressure is exerted to both side of the core by pressing devices foxed on to the shaft. The length of the rotor usually exceeds that of the poles by 2～ 5mm on either side－the effect being to minimize the variations in magic permeability caused by axial armature displacement. The periphery of the rotor is provided with teeth and slots into which the armature winding is inserted. The rotor winding consists either of coils wound directly in the rotor slots by means of specially designed machines or coils already formed. The winding is carefully insulated, and it secured within the slots by means of wedges made of wood or other insulating material. The winding overcharge are bent over and tied to one another with steel wire in order to resist the deformation that could be caused by the centrifugal force. The coiljunctions of the rotor winding are connected to the mutator mounted on the armature shaft. The mutator is cylinder made of small copper. 11 Segments insulated from one another, and also from the clamping elements by a layer of minacity. The ends of the rotor coil are soldered to each segment. On lowpower machines, the mutator segments form a single unit, insulated from one another by means of a synthetic resin such as Bakelite. To link the armature winding to fixed machine t