Additionally, the grouping of cables causes heat buildup since cables are in close contact, and there is oftentimes poor heat dissipation. In reality, there are several derating factors that increase the temperature experienced by cables.įor example, the thermal conditions of cables buried in the ground will differ from cables laid in, say, a duct or the air.
WIRE SIZE CALCULATOR FULL
Keep in mind that the full load current calculated in the previous section is for an ideal situation(ambient temperat ure).
By substituting these parameters into the equation, the full load current the cable needs would be approximately 234 A. So consider a scenario where there is the need to calculate the cable full load current for a 125 kW motor (Low Tension motor), which has an efficiency of 93% and is operated at 415 V and power factor of 0.8. This article will consider both single- and three-phase circuits, and the full load current for such circuits can be calculated as follows: Single-phase full load current formula The first step to take when specifying cable size is to calculate the full load current that the cable needs to cater for. Keep in mind that LT motors generally require more current than HT motors, so the wires are always thicker in LT motors than in HT motors. In contrast, Low Tension (or Low Voltage) motors usually supply below 440 V and have a rating of less than 150 kW. High Tension (also called High Voltage) motors usually supply above 1.1 kV and have a rating that is more than 150 kW. Motors typically fall under two categories: The article will also include some key electric motor wire sizing calculations and tables. This article presents four important factors that engineers must consider when specifying a cable wire size for their application. In contrast, undersized cables typically burn during operation, causing risk to human life, the motor, and infrastructure. For example, an oversized cable incurs unnecessary costsand power losses. Wrongly specifying cable sizes causes several undesirable effects.
Instead, they want to also select the right cable size for the motor and the application. It demands a ton of iterative steps, calculations, and design considerations to arrive at a system that works as expected.īut just because the motors have been specified, it doesn’t mean engineers should just take the plunge with installing and commissioning these motors. Engineers who have successfully sized and specified electric motors to meet their application requirements will agree that the design process is quite involved.
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