ALTERNATOR REGULATION AND OPERATION 



143 



When the coil axis ab roaches a'b', midway between pole centers, 

 the flux linking the coil is zero and the induced emf. A 

 maximum. Under the conditions assumed, the flux wave leads 

 the enif. wave by 90, as is shown in Fig. 147 (c). 



These space relations may also be shown by rotating vectors, 

 Fig. 147 (d). The vector </> is equal to the maximum value of 

 the flux linking the coil, and the vector E' \> equal to the maxi- 

 mum value of the induced emf. Each position of these two 



(d) 



I 



Coil 



A", iri L 



o ' '6 



FlO. 147. Relation of flux linking alternator <-oil to indum! voltage in coil. 



rot.Mti- tfl :i different position of the armature 



coil relative to tin- field poles. The instantaneous value of either 

 quantity. $ or >und by j)rojct inu it- vector on the verti- 



cal ;i\i- )')'. It is Been that the flux o reaches its maximum 



valil-' 'Ml i in advance of the emf. E'. 



i ml 1 17 iagrams. l-'imire 



OWB the flux linking tin- ec.il and the induced nuf. in the 

 coil for d: il as it i: 



to the field pol.-s. Figure 1 17 (d) -hows the.-e -a I lie qua lit I 1 



ors. 



