For phase converters serving variable loads, what is the minimum ampacity for the single-phase supply conductors?

In the context of phase converters used for variable loads, the requirement to size the supply conductors correctly is essential for ensuring safe and efficient operation. The correct response of 125% of the full-load amperes reflects the National Electrical Code (NEC) guidelines, which recommend that conductors feeding a phase converter should be sized to handle more than just the base load.

By sizing the conductors to 125%, it accommodates potential inrush currents and assures that the conductors can handle short-term overloads that can occur during the startup of motors or under fluctuating loads. This consideration is critical since the load characteristics may change and could lead to higher current demands than those measured during normal operation.

This requirement helps mitigate risks such as overheating of the conductors and ensures compliance with safety standards, which ultimately protects both the electrical installation and the equipment being powered. Proper sizing based on rolling up to 125% rather than lower percentages helps in maintaining longevity and reliability in electrical systems serving variable loads.