Series-connected Windings Research Articles

A new brushless wound rotor synchronous machine using a special stator winding arrangement

This paper proposes a new topology for a brushless wound rotor synchronous machine (BL-WRSM) using a specially designed stator winding supplied through a single three-phase inverter. In this topology, a special stator winding, which comprises of two sets of series-connected windings with an unequal number of turns, is used to generate an additional spatial sub-harmonic component in the stator magneto-motive force (MMF). This additional sub-harmonic MMF (SH-MMF) component is utilized for exciting the field winding of the BL-WRSM. The advantage of the proposed brushless topology is the use of a single inverter compared to a dual inverter used in the existing dual inverter BL-WRSM. For the rotor, there are two separate windings: (1) harmonic winding and (2) field winding. Both the harmonic and field windings are connected in parallel with each other through a rotating rectifier. The additional SH-MMF component generates a rotating air-gap magnetic field, which induces the voltage in the harmonic winding. This induced voltage is then rectified and used to supply a dc current to the field winding. A 2-D finite element analysis is performed to analyze and verify the operating principle of this new BL-WRSM.

Zero-current Switching Series Resonant High-voltage DC-DC Converter with Series-connected Primary Windings of Center-tapped Transformer

—This article proposes a novel zero-current switching series resonant inverter-fed voltage multiplier based high-voltage DC-DC converter. The series resonant inverter in the proposed topology has two power switches (insulated-gate bipolar transistors), two resonant capacitors, and only one high-voltage transformer with center-tapped primary windings. The power switches are connected in the form of a half-bridge network. The leakage inductances of the transformer's primary windings together with resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating power switches with an interleaved half-switching cycle. The secondary winding of the high-voltage transformer is connected to a voltage multiplier circuit to rectify and boost the voltage. The converter operates in discontinuous conduction mode, and its output voltage is regulated by pulse-frequency modulation. Therefore, all the power switches turn ON and OFF at the zero-current switching condition. The main features of the proposed converter are lower power loss, less cost, and smaller size compared to previously proposed series resonant high-voltage DC-DC converters. The experimental results of a 130-W prototype of the proposed converter are presented both for dynamic and steady-state operation. The results confirm the excellent operation and performance of the converter.

Study of a Novel Energy Efficient Single-Phase Induction Motor With Three Series-Connected Windings and Two Capacitors

This paper presents a novel energy efficient single-phase induction motor with three series-connected windings and two capacitors. By suitable selection of capacitors, the currents in three windings are approximately symmetrical, and thus, the motor can operate approximately symmetrically from single-phase supply. Based on the symmetrical components method, the condition for balanced operation is studied, and the method for determining capacitances is proposed. The performance analysis method is put forward to calculate the steady performances. Performance tests are performed on the proposed motor and three-phase induction motor. It is proved that their rated efficiency is approximately the same, while the power factor of the former is higher than that of the latter. In comparison with the ordinary single-phase induction motor, it has the advantages of higher efficiency and smaller volume, thus can take the place of the latter in some applications.

Characteristics of Two-Speed Capacitor Motors with Series-Connected Windings.

A method is given for calculating the characteristics of the series-connected windings capacitor motors by applying the theory of two-phase symmetrical components. This winding connection is effective to decrease the voltages of windings and capacitor. Experimental confirmation of the theory is included. Relation between the characteristics of the series connected windings capacitor motor and that of the parallel-connected windings capacitor motor are clarified. Two methods for speed adjustment of the series connected windings capacitor motor are discussed: (a) capacitor adjust type (b) extra-winding type. The principal characteristics, such as the slip for the maximum torque, and efficiency, are obtained taking into account the symmetric conditions. Characteristics of these two-speed capacitor motor are compared with that of the conventional capacitor motor with tapped auxiliary winding.

A three-phase magnetic amplifier: II--Experimental results

A model 3-phase magnetic amplifier is designed and tested to verify the theoretical analysis of Part I. The equivalent control circuit impedance and the core function of the magnetic material proposed are important factors in the determination of the response time and gain of the device. In addition, a feedback factor which is derived from the general analysis of an amplifier with both series-connected and parallel-connected control windings results in some interesting and unique properties. A cyclic integrator receives the signal from one phase of the output circuit which permits the integrator to reset between inputs. The theoretical response time is checked in the operating ranges of full to half output and half to minimum output for various significant combinations of control resistances in the series-connected and parallel-connected control circuits. Results for fast and relatively slow response times indicate a dynamic behavior which is in reasonable agreement with theoretical predictions.

A three-phase magnetic amplifier: I--An analysis

An analysis is presented of a 3-phase magnetic amplifier with bridge-connected output circuit and any number of series-connected and parallel-connected control windings. Approximate output difference equations are derived for two modes of operation representing one-half to minimum output and one-half to full output. These output difference equations express the dynamic relationship of the sixth-cycle average input and outputvoltages in terms of a core function and the control circuit resistances. The importance of a feedback factor associated with the fraction of the voltage from a gating core which appears across the cores in a position to be reset is demonstrated. Approximate gain and time constant expressions appropriate for a simplified dynamic representation are derived from the difference equations and a more complicated block diagram representation.