Problem 108-5    Source:   Problem prepared by the website authors.

Based on the results of the previous problem:

a) determine the total copper losses of the motor;

b) determine the mechanical power, P_mec, of the motor;

c) assuming FP = 0.8, what is the motor's input power?

d) assuming the motor efficiency is 75%, what is the motor's nominal power?

e) determine the rotational losses of the machine.

Solution of the Problem 108-5   

Item a

To calculate the total copper losses in the motor, we will use eq. 108-21, repeated below.

From the previous problem, we know that s = 0.05, P_Pgap = 843 W, and P_Rgap = 43 W. Therefore, substituting the variables with their respective values, we find:

Item b

To find the mechanical power, P_mec, of the engine, we can use eq. 108-27.

Item c

To find the input power, P_ele, of the motor we will use eq. 108-29.

Item d

The nominal power, P_nom, is given by eq. 108-31, repeated below.

Replacing the variables with their respective numerical values and performing the calculation, we obtain:

Item e

Using eq. 108-28, we can calculate the rotational losses of the machine, or

Item f

Using eq. 108-30 and after some algebraic work, we can calculate the losses in the iron of the machine, or