lEON UXDER PERIODIC MAG^"ETIZING FORCES. 101 



Attention will now be directed to a few of the more important 

 results contained in the foregoing tables. 



7. The iutluence of the wave form of H on the induction produced 

 can be clearly seen by comparing Tables III. and lY. In these two 

 series the periods of the oscillations were practically the same, bat for 

 the series in Table III., which was obtained by using the rotary con- 

 verter, the average wave form of H is given by — 



L = sin oit — -038 sin 3 {wt — So") — &c., 



while for the series in Table IV., obtained from the generator, the 

 average wave form of H is given by — 



M = sin Mt + -028 sin 3 (w^ — 15°) + &c. 



[L is of the peaked, while INI is of the flat type of wave form.] 



It must be remembered, however, that in every case H is due to 

 the magnetizing current which is px'oduced by the resultant e.m.f. in 

 the magnetizing circuit, and the components of this resultant are the 

 e.m.f. of the source (converter or generator as the case may be), and 

 the e.m.f. due to the reaction of the iron ring. 



In these experiments the latter was kept relatively small by using 

 a small sample of iron (as explained in sections 3 and 1), and by using 

 a high e.m.f of the source, the required magnetizing current being 

 obtained by insetting ironless inductances in the circuit. 



L and JNI are practically the wave forms of the e.m.fs. on open 

 circuit of the two sources used. 



On Fitr II. are plotted from Tables III. and IV. the characteristics 

 fx^, 0, b., and the iron loss I, against different values of B,, the ampli- 

 tude of the first harmonic of the induction, as abscissae, wheu these 

 two wave forms of magnetizing current were used, the period being 

 practically the same for both series. 



It will be noticed that though the iron loss points for both series 

 fall practically on the same curve, yet there are considerable differences 

 between corresponding values of the other characteristics. 



On referring to the formula for I in section 5, and to the values 

 for /a,, 7/^, etc., i,, 65, etc., in Tables III. IV., it will be found that in 

 the series with wave form L, I,, I,, etc., the energies dissipated in the 

 iron through the 3rd, oih, &c., harmonics are negative, while in the 

 series with the wave form M, I,, I., &c.,are positive. Thus, with wave 

 form L. electric energy which had been received from the magnetizing 

 circuit through the fundamental harmonic was reflected back to the 

 circuit by means of the liigher harmonics, while with the wave form M 

 electric energy was received from the circuit through all the harmonics 

 and dissipated as heat in the iron. 



As the total loss I is the same (r/.p.) for both, I, (i.e. energy 

 received by the first harmonic), in the case of L must be greater than 

 I, in the case of M, but (see section 5) — 



H,B, sin^_l sin^ 

 I, = :, ~. B; 



and as we find that and /x^ are both greater for L than for M, a small 

 difference in I,, that is iu sin 6 '/x„ for the same value of B, will cause, 

 as we tiuil, a large change iu the corresponding values of and /x^ for 

 the two .'<eries. 



