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On the Theory of Salient Pole Alternators with Electromagnet and with Permanent Magnet Excitations


Luo, Peilin (1952) On the Theory of Salient Pole Alternators with Electromagnet and with Permanent Magnet Excitations. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/M0ZN-HQ87.


I.The synchronous reactances of alternators with permanent magnet excitation and alternators with skewed armature slots:

The method for calculating the two reactances of salient pole alternators with permanent magnet excitation has been developed. Owing to the presence of the magnets, the direct axis armature reactance has been found to be much smaller than in electromagnet excited machines of similar sizes. The quadrature axis reactance is thus found to be likely the greater of the two.

The influence of skewing the armature slots has been studied, both for electromagnet excited and permanent magnet excited machines. It has been found that the general influence is to decrease the armature reaction reactances and to increase the leakage reactances. The influence upon the total reactances is to a certain extent to reduce the difference between the reactances along the two axes. Formulae are given for both types of excitation.

The practical correctness of the formulae when saturation is not appreciable has been confirmed indirectly by comparing calculated and tested regulation curves of two existing machines.

II. The cardioid diagram method of determining the voltage regulation of salient pole alternators and the load voltage increase phenomenon in alternators with permanent magnet excitation:

A graphical method has been developed for rapidly determining from two reactances the regulation of alternators for a wide range of power factor. The same method is used to study the performance of alternators with permanent magnet excitation. The study shows that it is possible to develop a system applicable to uniform rising regulation curves over a wide range of power factors from unity to that due to purely inductive load.

III. The optimum proportions of the field structure of permanent magnet excited alternators:

The optimum design of the field structure of permanent magnet excited alternators with specified lengths of air gap and stability has been obtained for two types of problems; viz., 1) when given space, to find the required maximum flux density in the air gap, and 2) when both space and the air gap flux density are known and the requirement is minimum weight of the magnets. A method of specifying the stability of the excitation magnets has been suggested.

It has been shown that appreciable improvements are possible for many existing designs.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Electrical Engineering, Physics and Mathematics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Minor Option:Mathematics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Sorensen, Royal Wasson
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1952
Record Number:CaltechTHESIS:12072012-090301560
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7312
Deposited By: Benjamin Perez
Deposited On:10 Dec 2012 16:09
Last Modified:11 May 2023 21:50

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