Design of a universal portable electric drill . p to give therelation between field ^nd armature turns dictated by the con-ditions for good cornnutation. The armature ampere turns perpole are usually less than the field ampere turns per pole andseldom exceed this figure in well designed machines. When we desire to operate this machine on alternating cur-rent we must reconsider these fundamental requirements in thelight of the new conditions imposed. Uur aim is to msiie theperformance on alternating current approximate the performanceon direct current. It is at once apparent that we must lamina
Design of a universal portable electric drill . p to give therelation between field ^nd armature turns dictated by the con-ditions for good cornnutation. The armature ampere turns perpole are usually less than the field ampere turns per pole andseldom exceed this figure in well designed machines. When we desire to operate this machine on alternating cur-rent we must reconsider these fundamental requirements in thelight of the new conditions imposed. Uur aim is to msiie theperformance on alternating current approximate the performanceon direct current. It is at once apparent that we must laminatethe magnetic circuit to prevent destructive heating from coreloss and that the re?^.ctance of the windings must be as low aspossible to give a tolerable power factor. The effect of thereactive components may be studied in the vector diagram x^ig. 10 2. THE FIELD. in a given field winding the field produced by alternatingcurrent is equal in effectiveness to that produced* by directcurrent. The coimter generated in the armature will be:. 19 ^ ~ x.^u-^essed e. m. f.^ GOTHiter e. m. ^ = induced e. m. f. in field induoed e. m, f. in armature/ drop in field and armature ^ = current angle of lag ^^^ = flux VECTOR DIAGRAM OF SERIES ALTERMTIIJG GimREJTT M050R FIGUl^E 10. ^ = series turns on armature N z= line!? yi - Un alternating current of the same effective value, or a maxi-mum value of ti/z ^ the generated in the armature will be: A/ ^^^ C kviax The only reason for a distinction is th^t it is custom-ary to use the maximum value of the flux in alternating currentcalculations; ^/VC^j^ gives the same effective value as repre-sented by N on direct current. One of the important considerations is the type of field;whether to be built v/ith distributed or concentrated winding,Ihe counter and consequently the speed of the armatureis independent of the distribution of the field flux, only thetotal number of lines need be considered and we are interest
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