Design of the field winding is to obtain the following information.

**Design of
field winding for salient pole Alternator:**

Design of
the field winding is to obtain the following information.

(i)
Cross sectional area of the conductor of field
winding

(ii)
Current in field winding

(iii)
Number of turns in field winding

(iv)
Arrangement of turns

(v)
Resistance of the field winding

(vi)
Copper loss in the field winding

Above
informations can be obtained following the following steps

(i)
Generally the exciter voltage will be in the range
of 110 volts to 440 volts. 15-20 % of

voltage
is kept as drop across the field controller.

Hence
voltage per coil V_{c} = (0.8 to 0.85) exciter voltage / Number of
field coils

(ii)
Assume suitable value for the depth of the field
coil

(iii)
Mean length of the turn in field coil is estimated
from the dimensions of the pole and the depth of the field windings. Mean
length of the turn = 2( l_{p} + b_{p}) + π (d_{f} + 2t_{i})
where t_{i} is the thickness of insulation on the pole.

(iv)
Sectional area of the conductor can be calculated
as follows

Resistance
of the field coil R_{f} = ζ x *l _{mt}*
x T

V_{c}/
I_{f} = ζ x *l _{mt}* x T

Hence a_{f}
= ζ x *l _{mt}*
x I

(v)
Field current can be estimated by assuming a
suitable value of current density in the field winding. Generally the value of
current density may be taken as 3.5 to 4 amp/mm^{2}.

Hence I_{f}
= δ_{f} x a_{f}

(vi)
Number of turns in the field winding T_{f}
= Full load field ampere turns / field current = AT_{fl}/ I_{f}

(vii)
Height of the field winding h_{f}
= AT_{fl} x 10^{-4}/ √(s_{f}
d_{f} q_{f})

(viii) Resistance
of the field winding R_{f} = ζ x *l _{mt}*
x T

(ix)
Copper loss in the field winding = I_{f}^{2}
x R_{f}

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Design of Electrical Machines : Synchronous Machines : Design of field winding for salient pole Alternator |

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