Physics · Ch 4 — Electromagnetic Induction and Alternating Current
Construction
Construction
A standard commercial alternator is built from two major parts, the stator and the rotor. The stator is the stationary part in which the armature winding is mounted, and it has two components: the stator (armature) core, a hollow, laminated cylinder made of iron or a steel alloy (laminated specifically to minimise eddy-current loss, exactly as covered in section 4.2), with slots cut into its inner surface to accommodate the coils of the armature winding, which is the actual coil wound into those slots. The rotor contains the magnetic field windings; its magnetic poles are magnetised by a DC source, and the ends of the field winding are connected to a pair of slip rings mounted on the same shaft about which the rotor turns, with a pair of stationary carbon brushes continuously sliding over these slip rings to maintain the electrical connection between the (stationary) DC source and the (rotating) field windings as the rotor spins. Sections …
What this figure shows. The stator is shown as a hollow, laminated cylindrical 'Stator core' with slots cut into its inner surface ('Armature slot') that house the coil of the 'Armature winding'. Nested inside it is the rotor: a 2-pole magnet assembly whose 'Field winding' is excited by a 'D.C. source' connected through 'Brushes' pressing against a pair of 'Slip rings' mounted on the rotor's shaft, with the rotor's N and S poles and its 'Magnetic axis of the field' clearly marked, and the armature conductors labelled P and S. The figure ties together every construction term used in the text: the armature winding sits fixed in the stator's slots while the DC-excited field magnet, carried on the rotor, physically rotates inside it, and the core is deliberately laminated (thin i …
Worked out. An enrichment panel, explicitly marked 'not for examination', gives a closer, more realistic look at a commercial alternator's construction through six labelled sub-figures: (a) the stator core shown with its empty slots before any winding is inserted, (b) a rectangular loop laid into one such slot, (c) the fully wound stator core with its complete armature winding and outlet terminal, (d) a 6-pole rotor built from salient (projecting) poles mounted on a magnetic yoke, (e) the same 6-pole rotor now shown with its excitation coil, slip rings, brushes and DC supply input wired in, and (f) the assembled stator core and rotor together. The box exists purely to make the earlier, more schematic 2-pole diagram (Figure 4.27) feel like an actual physical machine, and its content is explicit …