1.4.2 Turn Insulation

The purpose of the turn insulation in both random- and form-wound stators is to prevent shorts between the turns in a coil. If a turn short occurs, the shorted turn will appear as the secondary winding of an autotransformer. If, for example, the winding has 100 turns between the phase terminal and neutral (the “primary winding”), and if a dead short appears across one turn (the “secondary”), then 100 times normal current will flow in the shorted turn. This follows from the transformer...

|1.3.3|Form-Wound Stators—Roebel Bar Type, |1.4|STATOR WINDING INSULATION SYSTEM FEATURES, |1.4.1|Strand Insulation

1.3.3 Form-Wound Stators—Roebel Bar Type In large generators, the more the power output, the larger and mechanically stiffer each coil usually is. In stators larger than about 50 MW, the form-wound coil is large enough that there are difficulties in inserting both legs of the coil in the narrow slots in the stator core without risking mechanical damage to the coil during the insertion process. Thus,...

Section : [1.3], [1.3.1] , and [1.3.2]

1.3 TYPES OF STATOR WINDING CONSTRUCTION Three basic types of stator winding structures are employed over the range from 1 kW to more than 1000 MW: Random-wound stators Form-wound stators using multiturn coil Form-wound stators using Roebel bars In general, random-wound stators are typically used for machines less than several hundred kW. Form-wound coil windings are used in most large motors...

1.2.2 Insulated Rotor Windings and 1.2.3 Squirrel Cage Induction Motor Rotor Windings

1.2.2 Insulated Rotor Windings In many ways, the rotor winding has the same components as the stator, but with important changes. In all cases, copper, copper alloy, or aluminum conductors are present to act as a conduit for current flow. However, the steady-state current flowing through the rotor winding is usually DC (in synchronous machines), or very low frequency AC (a few Hz) in induction machines. This lower frequency makes the need for a laminated stator core less critical.       ...

1.2 PURPOSE OF WINDINGS & 1.2.1 Stator Winding

1.2 PURPOSE OF WINDINGS The stator winding and rotor winding consist of several components, each with their own function. Furthermore, different types of machines have different components. Stator and rotor windings are discussed separately below. 1.2.1 Stator Winding The three main components in a stator are the copper conductors (although aluminum is sometimes used), the stator core, and the...

1.1.3 Classification by Cooling

Another important means of classifying machines is by the type of cooling medium they use: water, air, and/or hydrogen gas. One of the main heat sources in electrical machines is the DC or AC current flowing through the stator and rotor windings. These are usually called I2R losses, since the heat generated is proportional to the current squared times the resistance of the conductors (almost always copper in stator windings, but sometimes aluminum in SCI rotors). There are other...

1.1.2 Synchronous Generators

Although induction generators do exist, particularly in wind turbine generators, they are relatively rare compared to synchronous generators. Virtually all generators used by electrical utilities are of the synchronous type. In synchronous generators, DC current flows through the rotor (field) winding, which creates a magnetic field from the rotor. At the same time, the rotor is spun by a steam turbine...