Watthour Meter Method Of Testing Instrument Transformers Classic Reprint

Excerpt from The Testing of Transformer Steel Consequently, methods of testing With alternating currents have come to be regarded as the only satisfactory way of making these measurements, and present efforts are directed to securing the best conditions for this form of test. In the wattmeter method, the electrical energy Which is supplied to maintain the alternating magnetization is measured With a wattmeter, While the maximum magnetic induction produced in the specimen is determined by a voltage measurement at the terminals of the magnetizing Winding or at the terminals of a secondary Winding placed around the same core of test material. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

Excerpt from Equipment for Testing Current Transformers The equipment and methods used for this purpose at the Bureau of Standards at Washington have been modified and enlarged from time to time to keep pace with the increasing demands in accuracy and range of the transformers to be tested. The object of this paper is to describe the equipment and methods 1 now in use at this Bureau in the hope that the data given may be of assistance to other labora tory workers who may wish to install apparatus for similar work. The accuracy needed in this class of testing should, if possible, be so high that errors in the certified values will be negligibly small in comparison with the inaccuracy likely to occur in the next step in the measurement process; that is, in the comparison in the field between the standard transformer and the working transformer. A limit to the possible accuracy is, of course, set by the repeatability of the transformer under test. This limit is influenced by a number of factors, among which are changes in the magnetic condition of the core as a result of previous operation, uncertainties in the temperature of the transformer windings and hence in their resistance, and uncer tainty in the exactness with which the burden used in the field is duplicated in the test. In the case of hole-type current transformers additional uncertainty arises because of differences in the position of [the primary conductor in the hole, and in the position of the return lead. The magnitude of the changes in calibration resulting from these effects depends greatly upon the type of transformer, but may amount to several tenths of 1 percent. The sensitivity of the present equipment is such that a change of percent in ratio and minute in phase angle is definitely detectable even at a secondary current as small as ampere. Changes in the performance of the transformer under test are there fore often noted. The accuracy of the equipment, since it involves the calibration of resistance standards of widely different values with the additional liability to errors from skin effect and residual self - induct ance, is, perhaps, not as high as the precision mentioned above would indicate. The accuracy limits printed on the Bureau's certificate form (viz, percent in ratio and 3 minutes in phase angle) are, however, certainly very conservative. In reducing the observed values all corrections are normally carried to the nearest percent and minute and the resulting values are then rounded off in the certificate to the nearest percent and 1 minute. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 edition. Excerpt: ...test, using the consumer's load, inserting the working standards in the low-tension side, but otherwise leaving the connections the same as in service (Figs. 299. 300 and 301). Light load tests may be made by loading the watt-hour meter from the low-tension side of the voltage transformer, if the capacity of the transformer will permit (Fig. 302). Where secondary tests are made at a low power-factor, using the consumer's load, the watt-hour meter should be adjusted to the value of secondary accuracy corresponding to the actual power-factor. If the watt-hour meter has been previously relagged with respect to the high-tension side, this renders the meter correct at all powerfactors. For method of determining the correction curve for use with instrument transformers and watt-hour meters, see Chapter V. CASE I.--Two-wire Watt-hour Meter With Only One Side Circuit Through The Watt-hour Meter. Fig. 261.--Watt-hour Meter Circuit Opened after Being Shunted. Fir.. 262.--Method of Introducing Ammeter for Testing on Consumer's Load. Fig. 263.--Final Connections for Testing on Consumer's Load. Pig. 264.--Connections for Testing with Voltmeter, Ammeter and Lamp Bank, Load Box, or Water Rheostat.-Connections for Testing with Wattmeter, or Rotating Standard and Lamp Bank, Load Box, or Water Rheostat. Fig. 266.--Connections for Testing with Calibrated Resistance and Voltmeter. Fig. 267.--Connections for Testing with Voltmeter, Ammeter, and Storage Battery. Fig. 268.--Connections for Testing cn Alternating Current with Wattmeter or Rotating Standard and Transformer. Note: When using an inverted current transformer or other transformer not adapted to the full voltage the rheostat should be inserted in the high-tension 01 low-current circuit. CASE...

Issues for Nov. 1949-Dec. 1953 include the Journal of the Southern California Meter Association.

Vols. for 1938-44, 1946- include an issue called the Instruments index, published sometimes as pt. 2 of a regular number, sometimes as an extra number.