Performance rotor losses

The performance of a motor is greatly influenced by a voltage unbalance in the supply system. It reduces its output and torque and results in a higher slip and rotor loss. This subject is covered in more detail in Section 12.2(v). For likely deratings, refer to Figure 12.1. Asystem with an unbalance of up to 1 % or so calls for no derating, whereas one having an unbalance of more than 5% is not recommended for an industrial application, because of a... 

The higher the full load slip, the higher will be the rotor losses and rotor heat. This is clear from the circle diagram and also from equation (1.9). An attempt to limit the start-up current by increasing the slip and the rotor resistance in a squirrel cage motor may thus jeopardize the motor s performance. The selection of starling current and rotor resistance is thus a compromise to achieve optimum performance. 

The effective friction loss, or gas-phase contacting power, is easily determined by direct measurements. However, the liquid-phase contacting power, supplied from the stream of scrubbing liquid, and the mechanical contacting power, supplied by a mechanically driven rotor, are not direc tly measurable the theoretical power inputs can be estimated, but the portions of these quantities effectively converted to contac ting power can only be inferred from comparison with gas-phase contacting power. Such data as are available indicate that the contributions or contacting power from different sources are directly additive in their relation to scrubber performance. 

Advanced two- and three-dimensional computer analysis methods are used today in the analyses of all critical components to verify aerodynamic, heat transfer, and mechanical performance. Additionally, the reduction of leakage paths in the compressor, as well as in the gas turbine expander, results in further plant efficiency improvements. At the compressor inlet, an advanced inlet flow design improves efficiency by reducing pressure loss. Rotor air cooler heat utilization and adt anccd blade and vane cooling arc also used. 

By comparison the induction motor has a much simpler rotor construction compared to the synchronous motor. When designed for use with variable speed drives the induction motor no longer has to satisfy the demands a direct online start which allows the design of the rotor to be optimized for performance. The rotor is constructed from simple copper bars, which are brazed to one-piece end rings and supported by a steel frame. By increasing the copper content it is possible to achieve significantly lower losses, higher efficiency and low temperature operation. In addition, the rotor has no insulated components. 

Radial actuator construction is very similar to that of an electric motor, involving the use of stacked laminations of sted, around which power coils are wound. Stacked laminations are also used in the rotor to minimize eddy current losses, which cause heating and otherwise represent inefficiencies between power supplied to the hearings, and the useful work performed by the bearing system. 

One of the most common sources of motor watts loss is the result of a motor not being properly matched to its load. In general, for standard NEMA frame motors, motor efficiency reaches its maximum at a point below its fiill-load rating, as indicated in Fig. E-5. This efficiency peaking below fiill load is a result of the interaction of the fixed and variable motor losses resulting in meeting the design limits of the NEMA standard motor performance values, specifically locked rotor torque and current limits. 

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