Ring Windings Research Articles

Propulsive characteristics of a novel linear hybrid motor with both induction and synchronous operations

This paper treats a novel linear hybrid motor (LHM) by both induction and synchronous operations, The proposed motor consists of one pair of linear synchronous motors (LSMs) and a linear induction motor (LIM). The primary-cores of both LSM and LIM have a common ring winding, and the secondary solid-conductor is arranged in both LIM and the interpole space of LSM. The feature of the motor is that the undesirable vertical force in LSM is offset by the symmetrical double-sided construction and the secondary is capable of self-starting by induction operation. From the investigation by the three-dimensional finite element analysis and experiment, we derive an optimal exciting condition for starting, and then verify that the proposed LHM is effective for practical use.

Investigation of Supplied Currents in Tubular Linear Induction Motor.

The linear induction motor (LIM) is structurally divided into the flat and the tubular-type. In this paper, we study one kind of tubular linear induction motor which has the primary configuration composed of four pieces of flat-type core. We call this type of motor “the square tubular LIM”. The tubular LIM has such a feature that its primary winding is a kind of ring winding, so we can independently supply the primary currents in each slot and hence easily obtain the various winding schemes. Though the square tubular LIM has various merits as stated above, the number of slots is usually limited in conventional applications.In this paper, therefore, we investigate the exciting current scheme with a view to improving primary magneto-motive forces. Firstly we determine the exciting current scheme in unloaded system by using polyphase alternating currents. Secondly we determine another exciting current scheme in loaded system by the hybrid finite element and boundary element method, and the augmented Lagrange multiplier method.Finally we confirm the proposed method by experiment.

Edge effect and independently supplied slot currents in tubular linear induction motors

The linear induction motor (LIM) is divided structurally into the flat and the tubular-type. This paper examines one kind of tubular linear induction motor whose primary configuration consists of four pieces of a flat-type core. We call this type of motor “the square tubular LIM.” The square tubular LIM has various merits of the cylindrical tubular LIM in addition to those of the usual flat-type LIM. The two remarkable features of the square tubular LIM that the flat-type LIM does not have are as follows. The first feature is that it has no edge effect, and the second is that the normal force in secondary conductor is cancelled by that of the opposite side of the secondary conductor. In comparison with the cylindrical tubular LIM, moreover, the square tubular LIM is easy to manufacture and maintain. The tubular LIM also has a feature that its primary winding is a kind of ring winding. Thus we can supply independently the primary current in each slot and hence easily obtain various winding schemes. Finally, the features of the square tubular LIM are studied. After numerically analyzing an experimental model, the motor is driven by the independently controlled slot currents, resulting in the expected performance.

Slotless-disc alternator with AC-side excitation

The paper examines a version of the double-disc alternator with AC-side excitation that uses a slotless stator. It is an interesting form of slotless machine because Gramme ring windings can be wound automatically on the strip-wound circular core and produce a mechanically secure unit. A basis for the design of this form of machine is described, and the main considerations which influence the choice of a suitable geometry are discussed. Experimental results demonstrate that the performance of the machine is satisfactory. Predictions of direct- and quadrature-axis reactances and full-load field current by standard synchronous machine methods are also adequate. A particular feature of the machine, the absence of stray loss in the solid rotor due to stator-slot permeance variations, is seen to be particularly beneficial. Eddy-current losses in the stator windings exposed to the main airgap field are examined and are shown to be relatively small but measurable. Methods of predicting these losses for round and rectangular conductors in both sinusoidal and uniform airgap fields are presented.

A cyclotron with a radially travelling magnetic wave

Possible designs for a cyclotron with a radially travelling magnetic field wave are considered and relations between the parameters are deduced. One or more radially travelling waves can be produced in the magnet gap by using separate ring windings fed from an a.c. source. Two possible systems are proposed. In the first, the travelling wave is responsible for accelerating the particles; in the second, a travelling field is superimposed on the normal fixed field and the particles are accelerated in the resulting total field. A region of stability (1 > n > 0) can be obtained and this must move outwards at the radial velocity of the particles. Stability is possible if the absolute field strength increases sharply from the inside to the outside of the acceleration zone. In principle, the system would allow the production of particles with energies as high as desired. In spite of the cyclic nature of the action, the mean beam intensity could well be better than that from a synchrocyclotron because of better focusing. Some approximate calculations are presented for accelerators of this type designed to produce various energies. It is shown that for a given energy the weight and size can be substantially less than for other types of accelerator.

The design of armature windings for direct-current dynamo-electric machinery

Section 1 deals with the electrical design of open-circuit windings on the high-voltage machines used in connection with arc lamps in series; and the Brush open-circuit generators. The small hand-driven generators used in insulation-testing sets are also mentioned. Attention is drawn to the fact that interpoles were not introduced before these designs were superseded. Closed-circuit windings are dealt with, and it is pointed out that ring windings have gone out of use except for the special cases mentioned. The drum winding is then discussed.Section 2 deals with mechanical design.Section 3 treats of the effect of the number and dimensions of the core slots in relation to various aspects of the design. Attention is drawn to the effect on commutation of slots containing coils of various numbers of turns. Mention is made of the points to be noted in selecting the number of slots and coils.Section 4 deals with limiting factors in design.Section 5 shows how the ratio of diameter to length of armature for the minimum inductance of coil is deduced, and draws attention to the loss due to inductance.Section 6 treats of the effect of coil pitch on both commutation and armature reaction. General formulae are given for the period of commutation.Section 7 discusses special connections and their use in increasing the number of commutator bars, and draws attention to the factors limiting the output of direct-current machines.Section 8 deals with the factors affecting the electrical balancing of windings.Section 9 discusses windings for special purposes.