Direct-current motor

A direct current motor comprising:

• a stator including a plurality of magnetic poles;
• an armature including an armature core having a plurality of slots, a plurality of windings wound around the armature core as concentrated windings, and a commutator having a plurality of segments connected to the windings, wherein the plurality of windings are connected to one another to form a single closed loop, and the armature core has an aspect ratio, which is the ratio of the diameter of the armature core with respect to the axial length of the armature core;
• and
• an anode power supply brush and a cathode power supply brush that slidably contact the segments,
• wherein one of following requirements i) to v) is satisfied:
• i) the aspect ratio being in a range of 3.2 through 5.6 when the number of magnetic poles is six, the number of slots is eight, and the number of segments is twenty-four;
• ii) the aspect ratio being in a range of 3.4 through 5.8 when the number of magnetic poles is eight, the number of slots is nine, and the number of segments is thirty-six;
• iii) the aspect ratio being in a range of 3.7 through 6.1 when the number of magnetic poles is ten, the number of slots is eight, and the number of segments is forty;
• iv) the aspect ratio being in a range of 3.7 through 6.1 when the number of magnetic poles is ten, the number of slots is twelve, and the number of segments is sixty;
• and
• v) the aspect ratio being in a range of 3.2 through 5.6 when the number of magnetic poles is six, the number of slots is seven, and the number of segments is twenty-one.