. A text-book of electrical engineering;. ply each side byV Iq ■ sin a —-.—j , we get the following equation, in which we have puta) instead of sin iy — a): — cos (90° -I- y E,^ + (J^)- \2 Sin a/ sin a , cos (go° + y — a) = In .sin a + \2 sm »/ ...(161). 336 Electrical Engineering Since j^ is the internal impedance of the machine, and is therefore con- ■0 stant, we see that the right-hand side of the equation is constant for allexcitations, for P^ and V are both unaffected by the variable the sake of shortness we may represent the right-hand side of theequation by R^- Now, an eq
. A text-book of electrical engineering;. ply each side byV Iq ■ sin a —-.—j , we get the following equation, in which we have puta) instead of sin iy — a): — cos (90° -I- y E,^ + (J^)- \2 Sin a/ sin a , cos (go° + y — a) = In .sin a + \2 sm »/ ...(161). 336 Electrical Engineering Since j^ is the internal impedance of the machine, and is therefore con- ■0 stant, we see that the right-hand side of the equation is constant for allexcitations, for P^ and V are both unaffected by the variable the sake of shortness we may represent the right-hand side of theequation by R^- Now, an equation a^-i- &2- 2«.6cos0 = c2 represents a triangle with sides a, b and c, of which the sides a and b enclosean angle 6. Equation (i6i) is of this form, and can therefore be represented Vby a triangle with sides E^, —:— and R, in which the two former sides^ ^ 2 sm a enclose an angle 90° + y — a. This leads to a very simple diagram, fromwhich the value of the angle y between the and vectors can be. ^^ TC- I 1 H 1 1 Volts 3600 3200 2800 2400 2000 ieoo 1200 800 400 Fig- 347 200 100 60 20 seen for any given value of E-^. From the point 0 in Fig. 347 a vertical lineOC is drawn equal to the terminal pressure V. Another line OA is drawn at Van angle a with the horizontal, equal to —;— . The point A is half as high 2 sm a ° as the point C. With A as centre^ an arc is drawn with a radius equal to R, equal to the root of the right-hand side of equation (161). A line OEis drawn, making any given angle y with OC, and meeting the arc at thepoint E. The triangle OAE must be the above-mentioned triangle, for itstwo sides OA and OE enclose the angle 90° + 7 - a and its third side is side OE is consequently equal to the E^, and it is ahead of vector OC by the angle y. The point E moves on the circular arc andgives the corresponding values of E^ and y. The diagram is actually drawofor the relations previously assumed,
Size: 1340px × 1865px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookidcu3192400440, bookyear1920
