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J. H. Neher and M. H. McGrath were two electrical engineers who wrote a paper in 1957 about how to calculate the capacity of current (ampacity) of cables. [1] The paper described two-dimensional highly symmetric simplified calculations which have formed the basis for many cable application guidelines and regulations.
For example, the United States National Electrical Code, Table 310.15(B)(16), specifies that up to three 8 AWG copper wires having a common insulating material (THWN) in a raceway, cable, or direct burial has an ampacity of 50 A when the ambient air is 30 °C, the conductor surface temperature allowed to be 75 °C. A single insulated conductor ...
Ohm's Law chapter from Lessons In Electric Circuits Vol 1 DC book and series. John C. Shedd and Mayo D. Hershey, "The History of Ohm's Law" , Popular Science , December 1913, pp. 599–614, Bonnier Corporation ISSN 0161-7370 , gives the history of Ohm's investigations, prior work, Ohm's false equation in the first paper, illustration of Ohm's ...
(E.g. 1 mm diameter wire is ~18 AWG, 2 mm diameter wire is ~12 AWG, and 4 mm diameter wire is ~6 AWG). This quadruples the cross-sectional area and conductance. A decrease of ten gauge numbers (E.g. from 12 AWG to 2 AWG) multiplies the area and weight by approximately 10, and reduces the electrical resistance (and increases the conductance ) by ...
They are based on "steady-state (equilibrium) ampacity" calculations. Emergency ratings are based on transient equations and models: they provide permissible overload ratings for a short and adjustable time (typically 5 to 30 minutes). Forecasting methods have been developed to determine intraday and day-ahead ampacity forecasts.
The power losses in the wire are a product of the square of the current ( I ) and the resistance (R) of the wire, described by the formula: P w = I 2 R . {\displaystyle P_{\rm {w}}=I^{2}R\,.} This means that when transmitting a fixed power on a given wire, if the current is halved (i.e. the voltage is doubled), the power loss due to the wire's ...
Ney Contact Manual - Electrical Contacts for Low Energy Uses (reprint of 1st ed.). Deringer-Ney, originally JM Ney Co. ASIN B0006CB8BC. [permanent dead link ] (NB. Free download after registration.) Slade, Paul G. (February 12, 2014) [1999]. Electrical Contacts: Principles and Applications. Electrical engineering and electronics. Vol. 105 (2 ...
Also called chordal or DC resistance This corresponds to the usual definition of resistance; the voltage divided by the current R s t a t i c = V I. {\displaystyle R_{\mathrm {static} }={V \over I}.} It is the slope of the line (chord) from the origin through the point on the curve. Static resistance determines the power dissipation in an electrical component. Points on the current–voltage ...