Rotor Pole face

Since the synchronous motor has an external source of excitation power it can maintain flux for a longer time during a fault. The rotor pole face construction and the field circuit help to maintain the air-gap flux and generated emf. The decay of flux during the fault is determined for the most part by the transient impedance of the synchronous motor. 

Typical results from an analytically based design procedure published by Howe et al. (1987) are shown in fig. 55. They relate to a motor equipped with pole-face mounted magnets, and have a specified short-time overload capacity. Howe et al. discussed the effect on magnet volume of a variable electric loading Q and variable rotor diameter D, the magnet being dimensional to withstand the overload. They show that increases in either D or Q result in a reduction in magnet volume. 

A similar situation occurs when the rotor pole axis is at right angles to the axis of the stator coils. Here the magnetic reluctance is at its maximum value due to the widest part of the air gap facing the stator coils. The complete reactance in this position is called the quadrature axis synchronous reactance Xsq . Deducting Xa results in the quadrature axis reactance X. ... 

Figure 1. Schematic drawing of a magic-angle spinning device. The Kel-F sample holder screws into a rotor base that is then loaded through the top of the coil. The stator is fixed and the spacing between the pole faces of the iron magnet is 25 mm other dimensions are to scale. Spinning speeds of 2 kHz can be achieved with 20 psi pressures and unfluted rotors, and over 3 kHz with fluted rotors. The sample volume is 420 fiL.

Three-Phase Synchronous Induction Motors. The synchronous induction motor has a conventional three-phase stator winding. The rotor is modified to provide cutouts for a specific number of poles on the rotor face to match the polarity of the stator winding and flux guiding barriers are included to improve the pull-in and pull-out torques. Figure 5.114 shows a typical rotor configuration for a two-pole synchronous induction motor. Similar configura-... 

The sensors are also oriented about the periphery of the stator, usually inside a ring that is motmted adjacent to the actuator poles. The photograph shows the sensor ring mounted on the end face of the radial stator. Inductive sensors are used that measure the inductance of the gap between the sensor and the rotor laminations. Two measurements are taken for each radial axis and the rotor center position calculated by means of a bridge circuit. 

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