The field winding should be designed for a voltageThe field winding should be designed for a voltage from 15-20% less than the exciter voltage.

The statement that “The field winding should be designed for a voltage from 15-20% less than the exciter voltage” pertains to the electrical engineering principles involved in designing the magnetic field system of electric machines, such as generators or alternators. The rationale behind this is to ensure that the field winding is not subjected to an excessive voltage that could potentially cause insulation failure or other types of damage.

In electrical machines, the field winding is responsible for generating a magnetic field necessary for the operation of the machine. This is typically achieved by passing a direct current (DC) through the field winding. The exciter voltage refers to the voltage used to drive this current into the field winding.

By designing the field winding to operate at a voltage that is 15-20% less than the exciter voltage, a margin of safety is included to accommodate for potential overvoltages or fluctuations in the system. This not only protects the field winding but also ensures the longevity and reliability of the electric machine as a whole.

This principle is especially relevant in the context of machines where the excitation system is separate from the main power circuit, such as in large generators used in power stations. In such systems, the exciter is often a smaller generator that provides the required DC current for the field winding of the main generator. Adjusting the exciter voltage to maintain it slightly higher than the designed operating voltage of the field winding allows for precise control over the magnetic field strength, and thereby the output characteristics of the