Problem 104-6    Source:   Example 5-5 - page 215 - KOTHARY - NAGRATH -    Book: Electric Machine - 4th edition - Ed. McGraw Hill - 2010

A DC generator in the independent configuration with lap winding has 16 poles and rotates at 200 rpm . The generator supplies a nominal load of 1,500 kW and its terminal voltage is 600 V. Determine:

a) the flux per pole if there are 2,500 turns per pole and the copper losses for rated load is 25 kW;

b) the area of ​​the pole shoe if the average flux density is 0.85 T.

Solution of the Problem 104-6   

Item a

In this problem we have that the multiplicity is m = 1. Then, the value of a, given by eq. 102-08, is:

Knowing that a = 16, P = 16 and Z = 2,500, we can calculate the constant K_a through eq. 102-14, or:

At this point we need to calculate the value of I_A. Using the power equation, we get:

The value of copper losses was provided in the problem statement. Therefore, knowing the value of I_A it is possible to calculate the value of R_A, because:

To find the value of E_A we will use the eq. 104-02. Soon:

As we know the value of E_A, using eq. 102-13 and after some algebraic manipulation, we arrive at:

Item b

To calculate the area of ​​the pole shoe, we know that Φ = B A, so: