Final answer:
The displacement of the currents in a resistance split-phase motor is typically between 30 and 90 degrees, essential for motor startup. Motor cores are laminated with insulated iron sheets to reduce eddy currents and resistive heating. Examples include a motor coil drawing 120 Amps with 0.400 Ohms resistance and a back emf leading to lower current and power dissipation under normal operating conditions.
Step-by-step explanation:
The displacement of the currents (phasors) in a resistance split-phase motor is usually between 30 and 90 degrees. This type of motor relies on a resistance to create a phase shift between the starting winding and the main winding currents, which is essential for motor startup. In resistance split-phase motors, eddy currents are minimized by constructing the core out of thin, electrically insulated sheets of iron. This construction helps in maintaining the magnetic properties while reducing resistive heating considerably. For instance, when motor coils with a resistance of 0.400 Ohms are powered by a 48.0 V emf, they draw a current of 120 Amps. Such coils dissipate a significant amount of energy as heat (5.76 kW), which can damage the motor if sustained. However, under normal operating conditions, where the back emf is factored in, the total voltage across the coils drops, leading to lower current draw and power dissipation. This is exemplified by a back emf of 40.0 V, resulting in a total voltage of 8.0 V across the coils and thus a current draw of 20 Amps.