Rotor Field

Synchronous-motor rotor frequency can be detected because the rotor field circuit is available. Special control schemes have been devised which take into account both speed and induced rotor current in providing locked-rotor and accelerating protection. 

The field phasor is a continuously rotating phasor in the space, whose angular position keeps changing with the position of the rotor with respect to the stationary stator. Let the rotor field displacement under the stationary condition with respect to the stator be denoted by angle /3as shown in Figure 6.11, This displacement will continue to change and will rotate the rotor (field frame). All the phasor quantities of the stator arc now expressed in terms ol the field frame. Figure 6.11 shows these two equivalent stator side phasors transformed to the rotor frame. 

Synchronous AC machines have a stator similar to the asynchronous machines, which has usually a three-phase stator winding. Whereas there are two types of rotor structures round cylindrical rotor and salient pole rotor as illustrated schematically in Fig. 5.6. The rotor field is generated by permanent magnets or a DC current winding, as reported in the same figure. In the first case they are called permanent-magnet synchronous AC machines. 

BG of IM in the Stationary and Rotor-Field Oriented Reference Frames... 

Fig. 8.33 Rotor flux and stator currents in rotor field-oriented reference frame...

To understand the directional control of the motor, it is important to note that a reversible ac motor has two sets of coils, one of which is fixed (the stator) and the other of which rotates (the rotor). One of these — say. the rotor — is powered from the 110-V power line and thus has a continuously lluctuating magnetic field associated with il. The output from the ac amplifier, on the other hand, is fed to the coils of the slalor. The magnetic field induced here inicracls with the rotor field and causes the rotor to turn. The direction of motion depends on the phase of the stator current with... 

Initial distribution and the predicted free surface boundaries within the twin-blade mixer represented by the mesh configurations shown in Figure 5.4, after 30, 60 and 90° rotation of the left blade are presented in Figures 5.5a to 5.5d, respectively. Samples of the predicted velocity fields after 30 and 45 ° rotation of the left rotor are shown in Figures 5.6a to 5.6b, respectively. The finite element... 

For a symmetric rotor the modification Eg to the rotational energy levels in an electric field S is larger than in a linear molecule and is given, approximately, by... 

Figure 9.24 shows part of the laser Stark spectrum of the bent triatomic molecule FNO obtained with a CO infrared laser operating at 1837.430 cm All the transitions shown are Stark components of the rotational line of the Ig vibrational transition, where Vj is the N-F stretching vibration. The rotational symbolism is that for a symmetric rotor (to which FNO approximates) for which q implies that AA = 0, P implies that A/ = — 1 and the numbers indicate that K" = 7 and J" = 8 (see Section 6.2.4.2). In an electric field each J level is split into (J + 1) components (see Section 5.2.3), each specified by its value of Mj. The selection mle when the radiation is polarized perpendicular to the field (as here) is AMj = 1. Eight of the resulting Stark components are shown. 

Plant capacity is a function of feed size distribution and Hberation. Separators can accept a size range as wide as 50—1000 p.m. Capacities are typically 1000 2500 kg/(h-m) based on rotor length which could be up to 3 m and have dia 150—250 mm. The feed should be as dry as possible because moisture interferes seriously with separation. Heaters are usually provided before the feed enters the charged field. Final cleaning is often conducted in electrostatic-type separators. Electrostatic shape separation, a newer form of ion bombardment separation, involves separation of particles based on shape and density without consideration to conductivities (37). 

Principle of Operation. Electrical current flows are induced in all conductors when exposed to an a-c field. These currents generate a magnetic field surrounding the conductors which oppose the field being produced by the a-c field with a force sufficient to repel the conductor. Eigure 16 illustrates this principle by showing a rotor consisting of many poles. 

The most widely used submerged-culture oxidizer is the Brings acetator (50). It uses a bottom-driven hoUow rotor turning in a field of stationary vanes arranged in such a way that the air which is drawn in is intimately mixed with the Hquid throughout the whole bottom area of the tank (51,52). In the United States, continuous cavitator units are used widely for cider-vinegar production. 

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