Measuring Power in Transformers. 189 



this time — that is, taking the average value of every term in 

 (3) it is to be observed that 



I rr+t m ip 



.dC=0, 



if C is the value of (J at the beginning and end of the period; 



M P i 



and hence, as p = ^ verv nearly, 



P 



Average VC = average RC 2 — average r^ CG t . 



If either or C were the current in a non-inductive 

 circuit, a great error would be introduced by endeavouring 

 to measure the average product by the split dynamometer 

 method; but there is no such error here. 



Hence Mr. Blakesley's method is correct, however great 

 may be the magnetic leakage. It must be remembered, how- 

 ever, that I have neglected eddy currents in the copper and 

 iron ; and I assume magnetic permeability to be constant during 



Now at full loads on this transformer it is perfectly obvious that 

 currents, lags, and powers are immensely altered by this small amount of 

 leakage which I have introduced as possible. The currents are ten times 

 as great, and the lags are utterly different from what they have been 

 supposed to be. 



Table I. — No Magnetic Leakage, or M = 1*5. 



p- 



i 

 A. A'. 



e. 



.'. j p. 



P'. 



Effic. 

 



a'. 

 100 



GO 



0-1000 , 



o 



89-9 



! 



179-9394J -0850 







999 



1412 0-9991 



44-97 



179-9395' 50-06 



49-85 



99-59 



99-82 



49-9 



0-2232 



1-9965 



26-50 



179-93951 99-95 



99-45 



9949 



99-61 



9-9 



0-9956 



9-913 



005 



179-940 11497 '8 



486-4 



97-70 



99-14 



4-9 



1-963 



19-61 







179-9409J981-7 



942-3 



95-98 



96-08 



0-9 



9 09 



90-95 







179-9468: 4545 



3722 



31-70 



81-85 



0-4 



16-67 



166-6 







179-9519 



8335 



5551 



66-61 



66-64 



01 



33-33 



333-3 







179-9610 



16667 



5554 



33-33 



3333 







50 



500 







179-9708 



25000 















Table II. — One and one-third per cent Magnetic Leakage, or M=l*48. 



► 



A. 



GO 



•1000 



99-9 



4412 



49-9 



•2228 



9-9 



•9627 



4-9 



1-741 



0-9 



3-370 



0-4 



3-658 



o-i 



3-726 







3-739 



A'. 



0-9858 



1968 



9-458 



1745 



33-28 



3611 



36-78 



36-91 



89-9 



464 I 



29-5 i 

 20-4 



30-4 ! 

 68-2 



77-6 i 



83-7 I 



85-8 ! 



179-931 

 181-5 



182-98 



194-8 



204-85 



•085 

 48-61 

 96-96 

 451-2 



750-8 



247-6 628-4 



257-33 i 392-8 



263-55 '204-4 



265-7 ! 136-9 



P\ Effic. 



a'. 







100 



48-54 99-70 



98-49 



96-65 99-68 



95-98 



442-8 98-13 



93-63 



720-7 96-01 



84-05 



498-2 79-27 



29-95 



260-7 66-37 



14-44 



53-75 26-29 



3-678, 



J 



i 







