Generator Coils Research Articles

A Turn Insulation Test for Stator Coils

Normally applied maintenance tests do not evaluate the condition of insulation between the turns of generator coils. The existing standards recommend neither methods of turn insulation testing nor values of voltage for testing turn insulation. This situation exists in part because of the difficulty in applying a proper test voltage to the turns without overstressing the ground insulation. Occasions arise, particularly with large hydro generators, where it is necessary to either test the turn insulation to assess the quality of the coils in a stator winding or else to completely rewind the machine.

Simplified determinations of heat transfer data for solids, applications to quality testing of electrical insulations

The first part of the paper describes a simple steady state apparatus for measuring the thermal conductivity of plates of electrical insulations, plastics, etc. The measurement is quick, requiring approximately 5 min. The apparatus also enables one to determine the thermal capacity of the sample. The second part of the paper describes the k-meter, a new device for measuring the heat transfer coefficient through the insulation on metal bars such as generator coils. The method does not require any access to the inner conductor. The suitability of the k-meter for nondestructive thermal ageing investigations of e.g. generator insulations and for quality control, is demonstrated. In this respect k-value measurements might be a valuable complement to dielectric loss measurements.

Review of Once-Through Steam Generators

Abstract This paper reviews the design concepts pertaining to the forced-circulation once-through steam generator. To aid the production engineer in evaluating different generators for application in different situations, this paper discusses elements of feedwater treatment, aspects of design, defines common terms the production engineer might not be familiar with, and describes several figures included for determination of heat requirements, pressure loss, generator thermal efficiency, heat losses, working pressures and tube spacing. Introduction The advent of high-pressure steam injection as a secondary recovery technique has created a requirement for a generator suitable for this application. The generally satisfactory and sometimes spectacular results achieved in several of the initial commercial steam flooding projects has created a rapid increase in the requirement for suitable generators. The result has been the appearance on the market of several competitive designs of thermal recovery generators. The production engineer is thus faced not only with the problem of understanding an unfamiliar piece of equipment, but evaluating the merits of several competitive designs. This paper is concerned only with reviewing the design concepts pertaining to the forced-circulation once-through generator. The high operating pressures used in this service dictate the use of a water tube design where the pressure is contained in relatively small tubes with resultant economy in manufacture and decrease in operating hazard. The once-through steam generator was specifically developed for thermal recovery applications and features a single pass of water through the generator coil and no separating drum. The units are generally designed to produce approximately 80 per cent quality steam, so that the weight ratio of water to steam at the outlet of the generator is about 1:4, which is a much lower ratio than in conventional boiler designs. This water-steam ratio is not sufficiently high to insure complete wetting of the tube walls in the outlet portion of the generator coil, therefore the maximum tube wall temperature must be determined using a steam rather than a water heat transfer film coefficient. Since the steam film coefficient will be considerably lower than that achieved with water at an equal mass velocity, the maximum tube wall temperature would be considerably higher than in a conventional boiler unless a lower radiant absorption rate is used. The method of calculating the tube wall temperature will be outlined later. The once-through generator was specifically developed for thermal flooding applications and provides features not available in conventional steam boilers. Among the important advantages are the following:1. It will handle feedwater with a relatively high percentage of solids, provided the solids have been converted to soluble form.2. It does not have a separating drum and is essentially only a pipe coil. Because of the small volume of water and/or steam contained in the coil and the lack of a drum, it does not conform to the classic definition of a boiler.3. It does not have level controls, low level cutouts, etc., as required in a conventional boiler installation, and does not require continuous blowdown and constant operator attendance. Feedwater treatment is an important consideration in the satisfactory performance of a once-through generator, and deserves special emphasis. Some of the main considerations are as follows. HardnessThe special nature of the thermal recovery heaters where 80 to 85 per cent of the feedwater is vaporized in a single pass through the heater makes it essential to have zero hardness in the feedwater at all times. We recommend the dual-ion-exchange system as providing the minimum hardness leakage in spite of difficult raw waters, with the maximum assurance of always providing this minimum hardness leakage. We believe an ion exchange system is a prerequisite for the successful operation of a wet steam injection system for secondary oil recovery. JPT P. 409ˆ

Reaction of Atomic Oxygen with Carbon

RECENT reports1–3 have indicated that the reaction of atomic oxygen with carbonaceous materials proceeds rapidly at room temperature and that the reaction has a zero activation energy. Investigations in this laboratory using several carbons have not confirmed these previous results. In the work recorded here, atomic oxygen was formed in a flow system (335 cm3 h−1 S.T.P., 0.13 mm mercury pressure) by the action of a high-frequency (28 Mc/s) electrode-less discharge. The oxygen gas was of British Oxygen Co. medical quality and was used without further purification. During the discharge the plasma was found to extend considerable distances down-stream from the generator coil. The extent of spread of the plasma could be limited by wrapping the glass tubing on either side of the generator coil with earthed aluminium foil. The concentration of atomic oxygen at the position of the carbon specimen was about 10 per cent. This concentration was measured calorimetrically using the method described by Schiff4. The carbon was contained in a silica boat and suspended in a silica reaction vessel. Facilities were available for outgassing the carbon at 900° C to pressures less than 10−5 mm mercury before reaction. The carbons used included purified Ticonderoga graphite crystals5, pyrolytic graphite, and various pure amorphous carbons.

A Cosideration Proportional Relations Between the 2nd Current Rapid Increase Point and AC Short-time Breakdown Voltage by AC Testing Method of Generator Coils

A Cosideration Proportional Relations Between the 2nd Current Rapid Increase Point and AC Short-time Breakdown Voltage by AC Testing Method of Generator Coils

AC Breakdown Voltage vs. 2nd Current Rapid Increase Point for Generator Coil

AC Breakdown Voltage vs. 2nd Current Rapid Increase Point for Generator Coil

The internal insulation of generator coils

TO DATE, no satisfactory test has been found which will evaluate the condition of the internal insulation of generator coils and reliably detect deterioration such as illustrated in Fig. 1

Controlled Radio-Frequency Generator for Production of Localized Heat in Intact Animal

In our previous paper 1 we have shown that it is possible to produce differential heating in vitro in an electromagnetic field. his heating is dependent on the radio frequency, on the magnetic field strength, and on the coercive force of the magnetic particles of Fe 2 O 3 , which are 0.02μ-0.1μ in size and which serve as the target material. In this paper we will demonstrate that we can produce differential heating in the intact animal even to the point of localized tissue necrosis. Examples of the temperature changes in the normal tissues during treatment will be shown. We will describe the apparatus for recording this temperature and also the characteristics of the radio-frequency field used. The contribution of the electronic scientist in this medical research program has been threefold: First, it was necessary to develop a radio-frequency generator and work coil; second, several types of magnetic particles had

Evaluation of the Internal Insulation of Generator Coils Based on Power-Factor Measurements

Evaluation of the Internal Insulation of Generator Coils Based on Power-Factor Measurements

Moisture Detection of Generator Coils by D. C. Dielectric Test

Moisture Detection of Generator Coils by D. C. Dielectric Test

Internally cooled generator coils increase ratings by one-half

A new method of cooling large turbine generators makes it possible to increase ratings by one-half. The technique consists of blowing hydrogen gas at high velocity through specially constructed hollow generator coils.

Nondestructive testing of generator insulation

A-C DIELECTRIC-LOSS TESTS: TEST TECHNIQUES based on dielectric measurements at operating frequency, originally developed for higher voltage insulations, have been applied to the insulation of generator coils. The volt-ampere requirements of the test voltage source may be reduced materially by resonating the capacitance of the generator winding with a variable high-voltage inductor.

An Unusual Incrustation on Generator Coils.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn Unusual Incrustation on Generator Coils.C. EhrenfeldCite this: Ind. Eng. Chem. 1909, 1, 3, 208Publication Date (Print):March 1, 1909Publication History Published online1 May 2002Published inissue 1 March 1909https://doi.org/10.1021/ie50003a023RIGHTS & PERMISSIONSArticle Views9Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (151 KB) Get e-Alerts