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Depending on the type of insulating material, common maximum allowable temperatures at the surface of the conductor are 60, 75, and 90 °C, often with an ambient air temperature of 30 °C. In the United States , 105 °C is allowed with ambient of 40 °C, for larger power cables, especially those operating at more than 2 kV.
The service factor is typically in the 1.15-1.4 range, with the figure being lower for higher-power motors. For every hour of operation at the service-factor-adjusted power rating, a motor loses two to three hours of life at nominal power, i.e. its service life is reduced to less than half for continued operation at this level.
The maximum load is the one that draws the greatest current, i.e. the lowest specified load resistance (never short circuit); is the voltage at minimum load. The minimum load is the one that draws the least current, i.e. the highest specified load resistance (possibly open circuit for some types of linear supplies, usually limited by pass ...
An electrical load is an electrical component or portion of a circuit that consumes (active) electric power, [1] [2] such as electrical appliances and lights inside the home. The term may also refer to the power consumed by a circuit.
This determines the peak momentary output power for a given load resistance. [1] [2] Current: The amp's output devices (transistors or tubes) have a current limit, above which they are damaged. This determines the minimum load resistance that the amp can drive at its maximum voltage. [3]
The most common three-phase system will have three hot legs, 208 V to each other and 120 V each to the neutral. An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral ...
The equation in section 310-15(C) of the National Electrical Code, called the Neher–McGrath equation (NM), may be used to estimate the effective ampacity of a cable: [3] = (+) (+), In the equation, T c {\textstyle T_{c}} is normally the limiting conductor temperature derived from the insulation or tensile strength limitations.
If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the current-carrying capacity. In practice, it is impossible to ensure the load does split evenly, so regulations require a thicker wire, of at least 2/3 the current capacity of the fuse or circuit breaker.