Problem 103-11    Source:   Adapted from Example 42.2 - page 872 - HUGHES, Austin -    Book: Electrical and Electronics Technology - 10th Edition - Ed. Pearson - 2008.

A 4 pole motor is fed with a voltage of 440 V and draws an armature current of 50 A. The armature resistance is equal to 0.28 Ω. The armature winding is wavy type and has 888 conductors . The flow in the machine is 0.023 Wb. Calculate:

a) the constant, K_a of the machine.

b) the turning speed of the machine in rpm.

Solution of the Problem 103-11   

Item a

In case the winding is wavy the value of a is given according to eq. 102-10, and its value is:

With these calculations we can calculate the constant K_a of the machine with wavy winding, using eq. 102-14 shown below.

So, replacing the variables by their respective values, we get:

Item b

To calculate the induced voltage in the armature, only the value of K_a changes. So, to calculate E_A, let's use eq. 102-13, shown below.

As we want to calculate the value of n, first we must find the value of E_A. Using the eq. 103-06, we get:

Therefore, replacing the variables by their respective values ​​in eq. 103-13, we find:

Carrying out the calculation, we get: