槽绝缘与匝间绝缘 毕业论文外文翻译.doc

外文资料ROTOR SLOT AND TURN INSULATION The most widely used AC motor is the squirrel cage induction motor (Section 1.2.3). The rotor consists of heavy copper, brass, or aluminum alloy bars welded to end rings and embedded in iron laminations. Alternatively, the windings may be cast-in-place aluminum alloy. The winding, without the laminations, resembles a squirrel cage, hence the name squirrel cage motor. The squirrel cage induction motor operates without sliding electrical contacts of any kind. There is generally no applied insulation between the conductors and the laminations, as the difference in conductivity of copper or aluminum versus iron laminations and the low voltage at which the rotor operates obviates the need. Most other types of rotors in motors and generators operate at higher voltages and have both ground and turn insulation (Section 1.5). Rotors in smaller machines are usually random- wound, using round enameled (magnet) wire (usually with a varnish dip) that serves both as turn and ground insulation. For higher voltage rotors, with either random- or formwound coils, separate slot and turn insulation is used. This insulation is usually made from formed pieces of materials that are set in place before the windings are installed. Alternatively, some small rotors use an electrostatic coating process to apply polymer powders to the slots for insulation. Materials selected for slot and turn insulation will vary depending on the temperature class of the winding and the voltage and power rating of the machine. Formed sheet materials may be of aramid paper (such as Nomex? by Dupont) for medium-size generators or laminates of plastic films and nonwoven layers for smaller machines. A very common slot insulation is called DMD [for a lamination of Dacron, Mylar, Dacron (Dupont trademarks)], with a suitable adhesive. DMD is made by Dupont and other suppliers from polyethylene terephthalate polyester resin in film and nonwoven fiber form. A series of similar lami