The testing of continuous current machines in laboratories and test-rooms Volume 1; a practical work for students and engineers - Tapa blanda
Sinopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ... to excite the machine, and another part is lost in the armature winding (ohmic loss). With a motor, of the electrical energy supplied a part is lost in exciting the machine and overcoming the ohmic resistance of its armature. The remainder is transformed into mechanical energy, from which, however, a part is lost in overcoming the mechanical and magnetic resistances. Hence three different kinds of efficiencies may be considered, viz. the mechanical, electrical, and combined or total efficiencies. The mechanical efficiency is of no special interest, and whilst in some cases the electrical efficiency is important, in all cases the combined, total, or commercial efficiency is of the greatest importance. i. The Electrical Efficiency As stated above, the electrical efficiency (ije) is the ratio between the electrical energy delivered to that consumed. Let Pc be the electrical energy consumed. Pd „ „ „ delivered. ra „ armature resistance (total, including the contact and brush resistance). r» „ shunt resistance. Ca „ armature current. Cm „ shunt current. r „ resistance of the series winding. Then--"' = Pd + (JaV+Tr; (23) for shunt machines, p "e = ftToiTTV.)' ' ' (24) for series machines, and p " = P7+Ca2(ra + r,)+emrm ' ' ' ' (25) for compound machines. Hence the electrical efficiency of a machine becomes determinable when the resistances of the armature and field coils are known. The measurement of these resistances is described in Chapter II. In the following are three examples for determining respectively the electrical efficiency of (a) A shunt machine. (1) A series „ (e) A compound „ (a) Shunt Machine. The machine is self-excited, and without a shunt regulator. Voltage, 110; cu...
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Reseña del editor
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ... to excite the machine, and another part is lost in the armature winding (ohmic loss). With a motor, of the electrical energy supplied a part is lost in exciting the machine and overcoming the ohmic resistance of its armature. The remainder is transformed into mechanical energy, from which, however, a part is lost in overcoming the mechanical and magnetic resistances. Hence three different kinds of efficiencies may be considered, viz. the mechanical, electrical, and combined or total efficiencies. The mechanical efficiency is of no special interest, and whilst in some cases the electrical efficiency is important, in all cases the combined, total, or commercial efficiency is of the greatest importance. i. The Electrical Efficiency As stated above, the electrical efficiency (ije) is the ratio between the electrical energy delivered to that consumed. Let Pc be the electrical energy consumed. Pd „ „ „ delivered. ra „ armature resistance (total, including the contact and brush resistance). r» „ shunt resistance. Ca „ armature current. Cm „ shunt current. r „ resistance of the series winding. Then--"' = Pd + (JaV+Tr; (23) for shunt machines, p "e = ftToiTTV.)' ' ' (24) for series machines, and p " = P7+Ca2(ra + r,)+emrm ' ' ' ' (25) for compound machines. Hence the electrical efficiency of a machine becomes determinable when the resistances of the armature and field coils are known. The measurement of these resistances is described in Chapter II. In the following are three examples for determining respectively the electrical efficiency of (a) A shunt machine. (1) A series „ (e) A compound „ (a) Shunt Machine. The machine is self-excited, and without a shunt regulator. Voltage, 110; cu...
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