When the capacity of the epoxy resin board exceeds 50 MW, the coil-shaped coil is too large, so that it is difficult to embed both sides of the coil into the narrow core slot without risking the mechanical damage of the coil.
When the capacity of the epoxy resin board exceeds 50 MW, the coil-shaped coil is too large, so that it is difficult to embed both sides of the coil into the narrow core slot without risking the mechanical damage of the coil. Therefore, most of the epoxy resin board nowadays no longer use multi-turn full coils, but are made of “half-turn” coils which are usually made of so-called rober transposition bars. With robel transposition bars Each time, only half of the coil needs to be embedded in the insulation system 9 of the core slot chapter 1 rotating electrical machine. This is much easier than embedding two sides of a full coil in two slots at the same time. With the transposition wire rod method, it is necessary to electrically connect the two ends of the wire rod to form a coil characteristics of the stator winding insulation system. The stator winding insulation system includes different components with different characteristics and combinations. Together to ensure that no electrical short circuit can occur that to ensure that the heat generated by the PR loss on the stator conductor which can be conducted to the heat dissipation device, but also to resist the effect of magnetic field force so that the conductor does not vibrate. Oxygen plate is a cross-sectional photo of a multi-turn coil. In addition to the main insulation components, this insulation system sometimes includes high-voltage anti-corona coating and winding end fixing components. The following sections describe the functions and various aspects of these components. The mechanical, thermal, electrical and environmental stress conditions the components are subjected to.
The top of the epoxy resin board is estimated to be in the stator. The strand insulation plays the role of turn insulation, although in more critical places, additional braided bushings are sometimes used alone to add main insulation or strong insulation with bad insulation sheets. Many mold-wound motors use separate turn and strand insulation. This section focuses on the strand insulation in mold-wound coils and wire rods. In the discrete pole windings, strand insulation will be used as turn-to-turn insulation to discuss insulated electromagnetic wires. Section 1.48 will discuss strand insulation also plays a role of transposition insulation. Each conductor in the mode-wound coil or bar is divided into multiple strands. Figure 1.8 Cross-section of the stator winding slots scattered around. Epoxy resin board has both electrical and mechanical reasons. For mechanical reasons, the conductor in the coil or bar of a large motor needs to carry a large current which requires it to have a relatively large cross-sectional area. In other words, a conductor with a large enough cross-sectional area can be obtained desired current carrying capacity. A single conductor of such a large cross-section is difficult to bend to form the required coil or bar shape. Large conductors composed of smaller strand conductors (also called single conductors or secondary conductors in split conductors) are easier to bend to form the required shape than single large conductors. For electrical reasons There are many reasons for making the conductor strands and insulating the strands from each other.
According to electromagnetic theory, if an epoxy resin board has a sufficiently large cross-sectional area, current tends to flow only through the outer surface of the foreign body which is the so-called skin effect. The skin effect causes most of the current to flow only through a certain depth layer on the surface of the conductor. At 6 Hz, the skin depth of the copper conductor is 8.5 mm, if the conductor cross-sectional area is large enough. When the radius is greater than 8,5mm, there will be no current flowing through the center of the conductor which indicates that the current does not make full use of all available conductor cross sections. The actual effect is that its AC resistance is higher than its DC resistance.