Five phase induction motor: Phase transposition effect with different stator winding connections

One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower derating factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower derating factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.

This paper introduces Hybrid Boost Modular Multilevel Converter (Hybrid Boost MMC) as a suitable candidate for subsea drive systems. The investigated drive system is based on a five-phase Induction Machine (IM) in order to enhance system's reliability and to gain other several merits of multiphase machines compared with conventional three-phase IMs. Each arm in the employed Hybrid Boost combines Half-Bridge (HB) and Full-Bridge (FB) Submodules (SMs) with ratio 2:1 respectively. The suggested Hybrid Boost MMC provides boosting capability with a reduced number of switches, which can be employed effectively instead of employing conventional voltage source converter followed by bulky step-up transformer. In addition, voltage balancing of the capacitors in any MMC is crucial in order to ensure proper operation of the converter. A sensor-less capacitor voltage balancing technique is proposed in this paper, employing five-level five-phase MMC with two HB-SMs and single FB-SM per MMC's arm. A simulation case study for the proposed system is investigated using a 1000 Hp five-phase Induction Machine (IM).

Three-phase induction machines are today a standard\nfor industrial electrical drives. Cost, reliability, robustness and maintenance free operation are among the reasons these machines are\nreplacing dc drive systems. The development of power electronics\nand signal processing systems has eliminated one of the greatest\ndisadvantages of such ac systems, which is the issue of control. With\nmodern techniques of field oriented vector control, the task of\nvariable speed control of induction machines is no longer a\ndisadvantage. The need to increase system performance, particularly\nwhen facing limits on the power ratings of power supplies and\nsemiconductors, motivates the use of phase number other than three,\nIn this paper a novel scheme of connecting two, three phase\ninduction motors in parallel fed by two inverters; viz. VSI and CSI\nand their vector control is presented.

Three-phase induction machines are currently the industry standard for industrial electrical drives. These machines are replacing dc drive systems for a variety of reasons, including cost, dependability, robustness, and maintenance-free operation. Three phase induction motors are operated as separately stimulated dc motors for field-oriented control. The advancement of power electronics and signal processing systems has eliminated one of the most significant drawbacks of such ac systems: the issue of control. The task of variable speed control of induction devices is no longer a disadvantage with modern field oriented vector control systems.  The desire to improve system performance, particularly when power supply and semiconductor power ratings are limited, promotes the usage of phase numbers other than three. In this chapter a novel scheme of connecting two, three phase induction motors in parallel fed by two inverters; viz. VSI and CSI and their vector control is presented and instead of using two inverters for three phase motor, a single multiphase motor design is discussed.

The development of electrical energy sources continues to grow along with the development of electrical energy, in line with the increasing electricity demand. One of the power plants developed uses a three-phase induction electric machine. Several studies have been conducted on this electric machine because of its many advantages, such as simple construction, easy control, low maintenance, and affordable machine prices. Three-phase induction machine analysis has been carried out. It is necessary to study the effect of rotor rotational speed on the power factor of laboratory-scale induction machines. The trick is to operate a three-phase induction machine with a network-connected operating mode. This research method requires an excitation current in the form of reactive power from the network. The prime mover drives the mechanically connected induction machine by increasing the rotational speed of its rotor. This technique is used to prove the change in the power factor of a three-phase induction machine and its effect when the rotational speed is changed. The results of the study are used to prove the analysis of the research that has been done so that the value of the power factor will be better when the rotational speed of the three-phase induction generator is increased.

Multiphase phase induction machines are usually modeled using multiple dq planes, where complete decoupling between these sequence planes is usually assumed. This assumption may be accepted if the magnetic circuit is assumed linear. However, at rated operating conditions, a degree of magnetic saturation is normally expected in induction machines, which breaks this generic complete decoupling assumption. Considering the saturation effects in multiphase induction machine, mathematical modeling has not been widely addressed in the literature. This paper introduces a five-phase induction machine model based on the well-known conventional dq model with multiple planes considering the effect of magnetic saturation. The flux correction method is used to represent the effect of magnetic saturation with modifications to include the effect of cross coupling between fundamental and third sequence planes due to the saturation effect. Experimental validation is carried out using a 1.5Hp prototype five-phase induction machine.

Coupling induction motors to improve the energy conversion process during balanced and unbalanced operation

Five-phase induction machines are generally modeled using multiple dq planes or using a phase variable model. This paper considers modeling five-phase induction machines using a voltage-behind-reactance (VBR) configuration. This configuration lends itself suitable for time-domain circuit-based simulators as the MATLAB/Simulink SimPowerSystems (SPS) toolbox. The stator electrical dynamics are represented in five-phase coordinates, while the rotor electrical circuit is modeled using rotor flux linkage as the state variable and expressed in the dq stator reference frame. The VBR model is equivalent to a conventional dq model; however, it facilitates the connection of an external inductance without affecting numerical accuracy and calculation efficiency. It also facilitates the simulation of different winding connections, series-connected multimotors, and open phase(s) conditions. The model is, first, derived for a magnetically linear system and then it is extended to include the effect of magnetic saturation. The flux correction method is used to represent the effect of magnetic saturation with a simple modification to represent the effect of cross coupling between fundamental and third sequence planes due to saturation effect. The dynamic cross saturation is considered by adding compensating terms that depend on magnetizing inductance variation. The proposed model is experimentally verified using a prototype 1.5-hp five-phase induction machine under different operating conditions.

This paper illustrates the control system of a five-phase wound-rotor induction machine that can be used in applications where, besides the torque generation, a certain amount of active power must be transferred to loads collocated on the rotor frame. This requirement is common in rotary assembly platforms, bottle filling and capping systems, that embed electric actuators, sensors and process controllers on a rotating disk. The use of a five-phase machine avoids the slipring contacts to feed the rotor load. However, the choice of the set-point values for the motor currents involves magnetic, electric and thermal constraints. The paper illustrates a methodology of analysis, and develops a technique to deliver power to the rotor loads through the third-order spatial component of the magnetic field, while keeping the motor torque under control and reducing the rotor current as much as possible to minimize the rotor Joule losses. The experimental tests on a scaled prototype demonstrate the practical potential of the machine.

This paper presents a viable transducerless rotor position and velocity estimation scheme for PWM inverter driven induction, synchronous, and reluctance machines with the capability of providing robust and accurate dynamic estimation independent of operating point, including zero and very high speeds, light and heavy loading. The injection of a balanced three-phase high frequency signal (500 to 2 kHz) generated by the inverter, followed by appropriate signal demodulation and processing combined with a closed-loop observer, enable the tracking of rotor magnetic saliencies from the machine terminals. Although rotor magnetic saliency is inherent within reluctance machines, and most synchronous machines, saliency in the induction machine is introduced via a modulation of the rotor slot leakage with minimal detrimental effects on the machine performance. Experimental verification for the induction machine is included. >

The aim of this paper is to present a new method for accurate three-phase induction machine fault detection using a simple torque excitation technique with the electrical drive. Since it is well recognize that side band harmonics around the fundamental are good candidates for electrical fault detection in three-phase induction machine, the magnitude evaluation of these harmonics is a tricky problem especially with non-sinusoidal power supply. The idea is to excite more these harmonics without high torque quality deterioration and to evaluate their magnitude for rotor fault detection and localization. The technique is presented and applied on a 11 kW-230V/400V-50 Hz-4 poles three-phase squirrel-cage induction machine.

This paper presents dynamic models of a three-phase induction machine in various reference frames widely employed in alternating-current (ac) machine analysis. The main objective is to derive and explain the machine model in relatively basic terms by using the idea of rotating reference frame theory. Many matrix manipulations and complex frame-to-frame transformations performed to obtain an advanced model from primitive dynamical equations are presented in a more compact and easy-to-understand way. Therefore, this paper reviews a detailed, yet simple and understandable mathematical background on the dynamic models of the induction machine. Furthermore, a unified and broadly applicable simulation model is proposed for simulating the dynamic behavior of the machine in any desired reference frame. The simulation model has also a modular and user-friendly structure. For the simulation studies, Matlab/Simulink environment is preferred due to its popularity. A Simulink machine model with several subsystems is explicitly given. The simulation study is realized for a small power induction machine operating under both load and no-load conditions. The variations of three-phase currents, electromagnetic torque, and rotor mechanical speed as well as the rotor flux-linkage components are shown. The key features of each reference frame are discussed, especially through the measured rotor flux-linkage components.

The aim of this paper is to compare different experimental techniques for detecting a stator inter-turn short-circuit in a Wound rotor induction machine working as generator. Three methods using different signals such as stator or rotor current and the leakage flux will be described and experimented. The rotor currents provide interesting signatures since the stator faults introduce new harmonics in the rotor windings. Hence, in this paper, it is proved that sensing one rotor current by using a current sensor is one of possible techniques for detecting this kind of electrical fault. The leakage flux is another alternative for this kind of problems since in this paper; it is proved that a simple external leakage flux sensor is efficient to detect, in the low frequency range, the intern-turn short circuit in three-phase induction machines even in presence of power supply harmonics. Stator currents space vector is also an interesting technique since it is proved that inter-turn short circuit faults can be considered as a stator unbalance which can be detected using negative sequence of stator currents. The comparison of these three methods is performed using experiments on a 5.5kW–220V/380V–50Hz–8 poles wound-rotor induction machine working in both healthy and faulty modes at different load conditions.

Chapter 3 - Modeling and Analysis of Induction Machines

This paper deals with the analysis of spatial harmonic components in multiphase single or double layer windings. It describes the methodology for magnetic field synthesis in the air gap and verifies the results on a five-phase induction machine using finite element method. The conclusion formulates general rules for spatial harmonics in multiphase induction motors.