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Papers by nazar Al-khayat

The paper discusses the modelling and testing of a large 500 kVA distribution type power transfor... more The paper discusses the modelling and testing of a large 500 kVA distribution type power transformer with iron cored disk-type windings. The models developed show a close trend between the measured and predicted frequency response. The results are believed to be very encouraging for further work in this area. Furthermore, the method used in this paper is sufficiently general to

The importance and necessity for an electrical machine design process where thermal and electroma... more The importance and necessity for an electrical machine design process where thermal and electromagnetic issues are considered in an iterative manner is clear today. A commercially available thermal modelling package is used to investigate the design of a TEFC synchronous machine for a mobile refrigeration application, which imposes significant demands on the thermal performance of the machine. Experimental results of a fully instrumented machine have been used to show that the software package predicts the thermal performance of the machine to a high degree of accuracy. Sensitivity analysis was used to optimise the machine for the required application

The following paper presents the method of poles position identification of the axial flux perman... more The following paper presents the method of poles position identification of the axial flux permanent magnet machine at zero and low speed. The identification is used for starting the motor in the demanded direction. The axial flux motor possesses a large number of poles which results in a small mechanical angle for magnet sector. The derived poles position identification by

This paper presents a novel method for parallel operation of adjustable speed power-electronic ge... more This paper presents a novel method for parallel operation of adjustable speed power-electronic generation systems. The proposed method is based on the well known droop scheme and therefore does not require any additional interconnections between units operating in parallel. Modifications and extensions to the conventional droop scheme are introduced to resolve problems specific for the parallel operation of adjustable speed generation systems. These include novel methods for connecting and disconnecting units to and from parallel system as well as method for sustaining required load sharing between units during sudden load changes. The results from the real laboratory system are presented to justify the proposed methods.

The paper discuss the design and performance of a laboratory rig which is used to evaluate differ... more The paper discuss the design and performance of a laboratory rig which is used to evaluate different variable/adjustable speed generating system topologies. A programmable torque speed characteristics of a DC machine controlled by a thyristor converter is used as simulator of the different driving engines. The electrical supply is provided by an axial flux permanent magnet generator and AC/AC converter. The converter produces a sinusoidal AC three phase voltage. The system was designed and tuned with PSIM 6 simulation software. Results of laboratory tests of step loads of the conventional adjustable speed generating system and hybrid with additional supercapacitor energy storage are presented. The results confirms the versatility of the test rig for development of an adjustable/variable speed generation systems.

This paper is focused on the performance of a novel type of adjustable speed power generating set... more This paper is focused on the performance of a novel type of adjustable speed power generating set. The set consists of a diesel engine, an axial type permanent magnet generator and AC/AC converter. The engine is designed to operate over a wide speed range powering a high efficiency permanent magnet generator. The generator output is fed to a power electronics controller designed to maintain the voltage and frequency to the requirement of the load. The power to weight ratio of the set is considerably more than conventional set incorporating a wound field generator and RIC engine running at 1500/1800 rpm. The axial flux generator used is light, short and higher in efficiency than conventional type. The unique feature of the system is the control algorithm, which ensures fast system response and accurately map the engine torque curve to load demand. The paper will present the concept and main features of the recently developed variable speed-integrated generating set.

Paper presents hybrid on-line UPS system (H-UPS). Presented system is based on a on-line (double ... more Paper presents hybrid on-line UPS system (H-UPS). Presented system is based on a on-line (double conversion) UPS. H-UPS consists of two controlled energy storage systems. The first one is a static energy storage system based on supercapacitor bank. The second energy source is adjustable speed generating system supplying DC link voltage. A control concept of the UPS operation, according short and long failure of the supply utility voltage is developed. The 5 kW H-UPS is designed, built and tested. The control unit is built using DSP processor based on Shark from analog devices. The design and system stability tuning is achieved using PSIM software. Laboratory tests confirm high quality of the produced AC voltage during transients (voltage failure) and during steady state operation without external supply voltage.

This paper is focused on the industrial development of a novel type variable speed power generati... more This paper is focused on the industrial development of a novel type variable speed power generating system that can be used for the supply of electrical loads in the range 10 kVA to 100 kVA. Variable-speed-integrated-generating (VSIG) sets consist of a diesel engine, an axial type permanent magnet generator and high frequency power converter that is IGBT based. The axial

... Bartlomiej Kaminski, Wlodzimierz Koczara, Nazar Al-Khayat* Warsaw University of Technology Ko... more ... Bartlomiej Kaminski, Wlodzimierz Koczara, Nazar Al-Khayat* Warsaw University of Technology Koszykowa 75, 00-662 Warsaw, Poland Phone: +48 (22) 234-5120 Fax: +48 (22) 622 ... Their main advantage comes from the lower voltage stress imposed on the switching devices. ...

Clinical Nutrition Supplements, 2003

... Axial gap machines generally take the form of a pancake design with a rotor that contains .... more ... Axial gap machines generally take the form of a pancake design with a rotor that contains ... The overall block diagram of overall variable speed (VS) power generation system is shown in ... 1. A permanent magnet generator PMG, driven by a prime mover En, is producing variable ...

The paper presents a variable speed stand alone generating system. Such system called also as adj... more The paper presents a variable speed stand alone generating system. Such system called also as adjustable speed generating system is a modern technique that has great number of advantages over conventional synchronous generator driven with constant speed. In the adjustable speed generating system the prime mover drives a permanent magnet generator producing variable frequency and amplitude AC voltage. The variable voltage is conditioned by an AC/AC power electronic converter providing high quality multiphase AC sinusoidal voltage. The decoupling of the speed of the generator and output voltage frequency provides new way for optimizing prime mover like reducing of rated power, weight, emission and size and other optimization activities. In such generating systems prime mover speed control strategy is very important subject of investigation. The paper shows methods of control speed in stand alone adjustable speed generating systems. The paper presents performance of variable speed generating system according to implemented methods of speed control. The generating system was also equipped with additional controlled energy storage system made from supercapacitor bank. Energy provided by the supercapacitors allows to achieve good performance of the generating system during transient states. A simulation tests preliminary verifier developed methods of speed control, whereas presented laboratory tests results of the variable speed generating system with/without supercapacitor controlled energy storage system validates quality of the output voltage during transient states caused by steps of load.

Paper presents decoupled variable (adjustable) speed generation system and its application in ren... more Paper presents decoupled variable (adjustable) speed generation system and its application in renewable energy generation. The decoupled generation system consists of internal combustion engine, permanent magnet generator and AC/AC converter. Performance of single decoupled generation set are discussed supported by results of laboratory tests. The variable speed system provides high quality voltage in wide speed range when the step of load is low. However, when the step load is significant the voltage drop is not acceptable. Therefore to provide high quality produced voltage an additional energy storage, made from supercapacitor and bidirectional DC/DC converter, is applied. Such system performs very stiff voltage in any load condition. Integration of renewable wind energy system is provided via DC link of the variable speed decoupled autonomous generation system. The priority of the power draw is from the wind source. This is assured by a method of three reference signals for the DC link voltage. Speed control of the driving engine in region of low specific fuel consumption results in high efficiency conditioning of the unstable (wild) variable renewable energy source.

Clinical Nutrition Supplements, 2003