36 Mr. T. H. Blakesley on Magnetic Lag. 



I have elsewhere explained : — 



a C*3 n n Iil 2 cos0 



cosfc ^ir for0B3 — 2~ ' 



We are therefore in possession of the two components of the 

 magnetic stress and of the angle between them. Hence we 

 are virtually in possession of the whole magnetic stress, and 

 its phase relatively to its components. If the resultant is in 

 quadrature with that component which results from the cur- 

 rent in the secondary coil, it is in the same phase as the 

 magnetization, which is in quadrature with that component ; 

 but not unless this is the case. 



Let the line A B represent mix or the magnetic stress in the 

 primary circuit, and let B C represent the magnetic stress in 

 the secondary, and let A B be the angle 6, found as above. 

 Then A C is the resultant magnetic stress. 



But the magnetization is in quadrature with B 0. Draw 

 AD at right angles to B C. Then CAD represents the 

 magnetic lag, which is seen to vanish if A C B is a right angle. 

 The condition of the existence of lag is therefore that 



CB< ABcos<9, 



which in terms of the dynamometer observations is 



C* 3 . 



^v / 2Ba 2 <m v / 2Aa 1 



V Atx-i Ba 2 



B* 2 <™C« 3 . 



^ n 



The observation on the dynamometer in the primary is seen 

 to be eliminated. Thus this question can be tested with two 

 dynamometers only. The amount of lag is represented by the 

 angle CAD. We can easily express its tangent in terms of 

 the three dynamometer observations. 



