Problem 103-4    Source:  Problem prepared by the website author.

Considering the engine from the previous problem, determine:

a) The power developed in the motor shaft.

b) Armature winding and field losses.

c) Whether the law of conservation of energy holds.

Solution of the Problem 103-4   

Item a

The shunt configuration of a DC motor is characterized by the circuit shown in Figure 103-04.1.

The mechanical power developed in the motor shaft is given by eq. 103-17, reproduced below.

Taking into account the data obtained in the previous problem, we have:

Item b

For the calculation of losses in the field and armature windings we will use the power equation, or:

Item c

To verify the Law of Conservation of Energy we must calculate the sum of the power generated in the motor shaft with the losses and obtain the value of the power supplied by the supply line, calculated in the previous problem. Thus, we have:

Substituting the variables for their numerical values ​​and performing the calculation, we obtain:

Value exactly equal to the one found in the previous problem, proving that the law of conservation of energy is valid.