The machine of Example 19.5 is to be used in a series connection. That is, the field coil is connected in series with the armature, as shown in Figure P19.16. The machine is to be operated under the same conditions as in Example 19.5, that is, n = 120 r/min and Ia = 8 A. In the operating region, ? = k I f and k = 200. The armature resistance is 0.2 ? , and the resistance of the field winding is negligible.

a. Find the number of field winding turns necessary for full-load operation.

b. Find the torque output for the following speeds:



1. n' = 2n 3. n' = n/2

2. n' = 3n 4. n' = n/4



c. Plot the speed–torque characteristic for the conditions of part b.


Analysis:



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