Spherical electric motors

The history of spherical motors is traced, beginning with the initial research in the mid-1950s. Interest grew in the 1960s in their use in space, due to their light weight compared with that of conventional motors. In the 1970s, the spherical concept was applied to pumps where the impeller is of spherical shape so that no shaft seals are required. The 1980s saw still more activity, this time with a heavy influence on analysis. The complicated geometry of the motor, which results in a high production cost and does not seem to enhance reliability, has prevented commercial success. It may prove useful for large weightless structures to be constructed out in space     

On reducing the vibration and noise level of induction motors with integral and fractional slot windings

Contents The paper presents a method of calculating the radial magnetic forces and pulsating torques in induction motors with integral and fractional stator slot winding and squirrel-cage rotors, which aims on reducing the forces of vibration and the noise level of electromagnetic origin. The method leads to a proper choice of stator and rotor slot numbers and other design data, which allow to avoid cases where force components of considerable value and frequencies in the resonant band of the motor are generated. Special attention is paid to the generation of time dependent (synchronous) parasitic torques and their frequencies. Finally the paper includes the experimental verification and presents a case of successful application in a high power motor.

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Die Reduktion des Schwingungs- und Geräuschniveaus von Induktionsmotoren mit Ganzloch- und Bruchloch-Wicklung des Ständers

Übersicht Im Beitrag werden Methoden zur Berechnung von magnetischen Radialkräften und Oberschwingungsanteilen des elektromagnetischen Moments von Induktionsmotoren mit Ganzloch- und Bruchloch-Wicklungen des Ständers und Käfigläufern vorgestellt. Ziel der Berechnung ist die Reduzierung von Schwingungen und Geräuschen elektromagnetischer Herkunft.Diese Methoden helfen bei der Auswahl der Nutzahl von Ständer und Läufer sowie anderer Konstruktionsdaten. Damit können Oberschwingungsanteile von auftretenden inneren Kräften derart beeinflußt werden, daß Komponenten, die im Bereich der mechanischen Eigenfrequenz des Motors liegen, nicht auftreten. Besondere Aufmerksamkeit wird den frequenzabhängigen Oberschwingungsanteilen des Momentes gewidmet. Es werden experimentelle und theoretische Ergebnisse, die anhand eines Motors großer Leistung gewonnen wurden, gegenübergestellt.

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List of main symbols k _s ,k _r stator and rotor winding factors - k _sk skewing factor for -harmonic - N _s ,N _r number of stator and rotor slots - p number of pair-poles - q number of stator slots per pole and phase - s slip of rotor in respect to fundamental harmonic - angle around the rotor surface - airgap width - magnetomotive force (MMF) - magnetic conductance - integers denoting transformed rotor currents - integers assigned to harmonics (fundamental =p) - integers assigned to harmonics (fundamental =1) - _r rotor position angle - ₁,f ₁ pulsation and frequency of supply voltage - angular speed of the rotor     

Reliability testing of electric motors

Several motor failure mechanisms and test methods to determine whether a motor is suitable for extended service are discussed. Application and limitations of these test procedures are described. It is concluded that motor windings fail because the magnetic forces which turn the rotor also cause motion and therefore abrasion in the windings     

Acceptance testing of electric motors and generators

A comprehensive inspection and acceptance-test program for electric motors and generators of 300 HP (225 kW) and larger is outlined. Induction and synchronous machines are included, and references are made to IEEE, ANSI, and NEMA standards for the electrical tests. Recommended electrical and mechanical inspections and tests are described, and bearing housing and shaft vibration limits are recommended for all types of electric machines. The mechanical test procedures and vibration limits described are proposed for inclusion in future editions of IEEE and NEMA standards. An inspection and test matrix for highly critical special-purpose and less critical general-purpose machines is given     

Asynchronous electric motors for variable-frequency electric drives of drilling rigs

Operation peculiarities of the main drilling rig mechanisms are considered. The key specification requirements to asynchronous variable-frequency electric motors of the main drives are presented. The possibility of designing and developing the batch production of competitive, domestically produced drilling electric motors at enterprises of RUSELPROM concern is grounded.     

The calculation of stepper and synchronous electric motors for automobile electric drives

Peculiarities of calculations for electric motors for automobile electric drives integrated with electronic controls are considered.     

Combined linear electric motors for robotic systems

The principles of design, construction, and characteristics of special linear electric drives based on combined linear induction motors (CLIMs) for moving robotic trolleys in sealed radiation chambers have been considered. Existing systems have been equipped with gear motors having a cable power supply or chain conveyors. In addition, the mechanisms of electromagnetic coupling have been used. Conventional LIMs with complex control systems or frequency converters are sometimes used in such systems. The proposed construction of electric drives based on CLIMs is much simpler and more reliable. These motors consist of induction driving units and braking units based on permanent magnets. Acting together, these units make it possible to obtain a low speed of trolleys without using any complicated control system or frequency converters. Experimental research and industrial implementation have shown the effectiveness of application of the proposed special CLIMs, the use of which improves the performance and reliability of equipment in a radioactive environment.     

Noise characteristics of electric motors of variable-frequency geared electric drives for elevators

The possibilities of improving noise characteristics of geared drives with single-speed asynchronous electric motors and variable speed of rotations are considered.     

Smooth regulation of the exciting current in tractional electric motors

Pulsed regulation of the exciting current in dc tractional motors is considered. This method is superior in numerous respects to classical stepwise rheostat regulation. Pulsation and control characteristics of the pulsed regulator are presented.     

Electromagnetic noise of induction motors driven by PWM inverters

When a squirrel cage induction motor is driven by a PWM inverter, electromagnetic noise different from that during commercial power source drive is experienced. This is because of sideband wave voltage induced in PWM inverter output voltage. This paper first describes the mechanism of electromagnetic noise generation in commercial power source drive, and then electromagnetic force considering the sideband frequency and voltage content and the mechanism of electromagnetic noise generation in PWM inverter drive. It also refers to the sideband frequency and voltage content because of operating time control. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 55–62, 2000     

Methodology of no-load testing of reconditioned induction electric motors

Original methods for testing reconditioned short-circuit induction motors are presented. We discuss the problems of how to determine a motor’s parameters for the case when experimental data is not complete.     

导波雷达液位测量装置在大型火力发电厂的应用

导波雷达液位计采用了TDR(时域反射)原理,电磁波传播不受介质密度、介质粘度、介质蒸汽、液面波动、液面泡沫的影响,对液位的测量精确,并且能耗低,在大型火力发电厂液位测量方面有广阔的应用前景。     

The origin and reduction of acoustic noise in doubly salientvariable-reluctance motors

An experimental study of the acoustic noise emitted from an inverter-driven doubly salient variable-reluctance motor (VRM) is presented. A list of possible noise sources is given. Through a series of experiments, all but one source is eliminated as being important, and the remaining source is shown to be dominant. The dominant noise source is the ovalizing deformation of the stator due to its radial magnetic attraction to the rotor. The emitted noise is particularly strong when the frequency of deformation coincides with that of a natural mechanical resonance of the stator. Several methods of reducing acoustic noise emission are studied. One successful method is the introduction of dither into the control of the motor in order to spread the spectrum of noise excitation and reduce its coupling to the mechanical resonance of the stator     

Electronic control of electric motors in railway automation systems

Special linking circuits are required for the design of safe railway automation and remote control of trackside objects. They are usually based on devices with an asymmetrical failure rate, mainly first reliability class electromagnetic relays. The development of railway automation and remote control devices requires the use of state-of-the-art contactless semiconductor components. In this case, the use of functional converters or periodic testing of semiconductor switches and disconnection of the power supply from control objects in case of faults are needed. This article describes the use of a three-phase induction motor as the solution of the problem. They are used for the design of functional converters for railway automation electric motors control. It is proposed to use the low-frequency mode of power switch operation (switch frequency is 50 Hz) and to abandon the pulse-width modulation. The suggested technical solution is used in a CBI-MPC system for train traffic control at stations developed at the Center for Computer Railway Technologies of St. Petersburg State Transport University.     

中小电机市场发展空间凸现

中小型电机是量大面广的产品,耗用的电能占全国总发电量的60％以上,广泛应用于工业、农业和国民经济其他部门。     

电能计量装置的改造

针对油田热电厂110 kV系统10条输电线路电能计量装置存在的问题,进行了详细分析并提出了解决方案,实施后使电厂侧计量回路最大存在-2%的计量误差降低到-0.08%,达到了电力计量标准DL/T448-2000中规定的要求,每年可减少销售电量计量损失约5 × 107kW·h.     

电能计量装置的改造

电能计量装置改造应是城网改造的组成部分。随着城网的建设与改造 ,电能计量装置中存在的差错应当引起重视 ,予以改正。1　选用正确的计量方式常见的不正确的计量方式有以下几种 :(1 )三相四线回路安装一只单相电能表 ,将表读数乘以 3即算作三相四线总电能。(2 )三相四线低压线     

A comparison of the energy efficiency of the traction electric drive of alternating-current electric locomotives based on collector and asynchronous motors

An assessment of the overall performance of 3ES5K alternating-current electric locomotives with a collector drive in the regimes of traction and recuperative braking using the concrete example of a staged route between the Khabarovsk-2 and Bikin stations of the Far East Railroad is given in this article. Real traction and brake characteristics of a 3ES5H electric locomotive in the case of a cargo train of large weight and length are shown. Analysis is carried out of all the characteristics of a 3ES5H electric locomotive, and they are compared with the movement of a 2ES5 electric locomotive with an asynchronous drive. It is determined why 3ES5K electric locomotives are more power efficient than 2ES5 ones.