Origin of 118V Rating

In the early days of alternating current (AC) power, the standard frequency in the United States was 60 cycles per second (cps). However, the voltage levels used to power loads varied significantly, with some systems operating at 100V, 110V, or other values.To standardize the voltage, the National Electric Code (NEC) established 115V as the nominal voltage for lighting and small appliance circuits in 1911. This voltage was chosen because it was a compromise between the higher voltage systems used for power transmission (220V) and the lower voltage systems used for lighting (100V).However, some loads, such as motors, required higher voltages to operate efficiently. To accommodate these loads, the NEC allowed for special 118V circuits. These circuits provided a slightly higher voltage than the standard 115V circuitos, reducing voltage drop and improving performance.

Relationship to 230V

The voltage levels used in the power grid are interconnected. When the frequency was changed from 60 cps to 60 Hz in the 1950s, the nominal voltage was also increased slightly to 240V to maintain the same power output.Prior to the frequency change, 230V was indeed the nominal voltage for power transmission. This voltage was still used in some industrial and commercial applications after the frequency change, and it is still commonly used in Europe today.

Conclusion

The 118V rating for certain loads was established to provide a higher voltage for efficient operation of motors and other devices. This rating was based on the standard 60 cps frequency and the nominal 115V voltage used for lighting and small appliance circuits. With the adoption of 60 Hz frequency, the nominal voltage was increased to 240V, but the 118V rating for certain loads remained in use. Flag for review