Stator Windings 187

188 Chapter 9

190 Chapter 9

Various forming machines have been devised to receive the hairpin coil and to then reshape it into the form that is required, such that one coil side will fit into the bottom of a stator slot and the other coil side will fit into the top of another slot, one coil throwaway. Coil-forming machines differ in detail and in degree of mechanical sophistication, but they have several general principles in common. The hairpin coil is placed into the forming machine, and jaws or pairs of plates then clamp the coil at various locations along its two sides and two ends. Controlled force is applied to the various clamp positions to cause movement of parts of the coil relative to each other, as follows:

Stator Windings 193

194 Chapter 9

Stator Windings

TABLE 9.1 Approximat~ Properties of Three Electrical Conducting Materials

Metal (%)a

Electrical conductivity 57-60 94-97 100

Thermal conductivity 48 93 100

Specific heat (Weight)b 383 165 100

Specific heat (volume)c 99 140 100

Density 26 85 100

Costd 0.72 0.77 100


The relationship between flux density B and the corresponding magnetic field strength that produces it is

Equation (9.4) may be expressed with B in units of maxwells/in.2 and with w in units of inches by remembering that 108 maxwells equal 1 weber and that 39.37 inches equals 1 meter. Then

w maxwellS/inch 2 (9.6)

Equation (9.5) remains unchanged as long as consistent units are used for y, d, Bm, and B.