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Correctly sizing a VFD Cable for your drive and motor is really not difficult if you know where to look. By knowing what sections of the National Electrical Code (NEC) to ref- erence, you can correctly size cable conductor size for your system. Just follow these five simple steps to size cables for low voltage drive systems with operating voltages not greater than 575 volts. STEP ONE: Determine the minimum temperature rating of your equipment. Temperature ratings are important to know when derating the cable for the application as higher temperature ratings allow cables to handle more current. The NEC tables for ca- ble ampacity for low voltage cables have columns for 60°C, 75°C and 90°C. The column you use will be based on the minimum temperature rating of your drive terminals, your motor terminals, and your VFD Cable. Most drive terminals are rated for 75°C. All Southwire VFD Cables carry a 90°C conduc- tor temperature rating but this is not true of all VFD Cables from other manufactures. Motor terminal temperature ratings can vary from 60°C to 90°C. Each of these temperature ratings needs to be verified with the manufacturer’s datasheets or user manuals. If other equipment is being used that is in the cable’s path, like a quick disconnect, collect that devices temperature raring too. Once you have all the temperature ratings, record the minimum value.

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Southwire® Industrial Power Cable products do not have a defined shelf life. These products are composed of hard goods (metal, polymer, etc., ...) that are designed for many years of service once installed. As long as the products are not damaged during storage/handling and they are stored in a facility that protects against exposure to weather (sunlight and precipitation), there should be no degradation to the electrical and mechanical performance of the products and no reduction in service life. When storing cable the following precautions should be considered

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DC Hi-Pot Testing is used for proof testing shielded cables (5kV to 46kV) in the field. The test can be done at various times such as acceptance of new cable installation, maintenance testing to track insulation degradation and as a pre and post test for splicing existing cables to new ones. The test will expose gross imperfections that are caused by improper handling, installation techniques or termination workmanship. A DC Hi-Pot test is not capable of locating the point of failure, rather it gives you an assessment of the whole system.

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Strand-fll sometimes called moisture-block is a tar like substance that is applied between each lay-er of a concentric stranded copper or aluminum phase conductor. During the stranding process and at slightly elevated temperatures this tar like substance becomes fuid enough to be forced through a pump and applied geometrically in such a manner that the interstitial space between every strand is flled with the tar. The tar is then allowed to cool whereas it becomes stable and remains in place.

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A dual rated cable is a cable that lists two different voltage ratings on its jacket. For instance, a cable with 115 mils insulation thickness may have a jacket with a print legend that lists both 5kV and 8kV voltages at 133% and 100% insulation levels respectively on it. Therefore, this cable may be used on both 5kV and 8kV systems.

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The objective of this procedure is to provide a means of repairing jacket gouges, tears or indents in low and medium voltage cables. The purpose of the jacket is to protect the underlying elec- trical components from physical and environmental damage. The jacket is not part of the cable’s electrical system and therefore serves no dielectric purpose. Repairs should only be performed by qualifed personal.

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Southwire is a company with a keen environmental awareness. We seek to leave the lightest footprint possible on the environment in the course of manufacturing and delivering our products to market. To that end Southwire Company has innovated a product that accomplishes one of our environmental objectives – A medium and 600 volt Ethylene Propylene Rubber (EPR) insulation that contains no lead.

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Background Southwire’s Medium Voltage Switchgear and Substation Cable is a non-shielded, insulated, finely stranded cable that has no voltage rating. The cable has no UL listing and is not recognized by the National Electrical Code (NEC). The cable’s primarily use is for installation in medium voltage switchgear, motor controllers, and substations. In regard to use inside enclosures and equipment, even though this cable itself is not UL listed, a UL approval can be obtained on the complete assembly by having the system tested and approved.

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Overview While it is acceptable to terminate the phase conductors of a VFD cable as you would any other industrial power cable, special attention needs to be paid to the termination of the cable shield. The shield is an important part of the VFD cable but if it is not terminated properly, most of the benefits that this shield provides are negated. If you don’t properly terminate a VFD cable’s shield you may as well have not spent the extra money on VFD cable to begin with! Proper shield termination allows the shield to become a low impedance path for high frequency common mode current to flow from the motor back to the inverter. Without this controlled path, these currents can travel through motor bearings and building infrastructure and cause problems with other sensitive equipment like PLCs, control, and communication systems located throughout your facility. There are three main types of shield found in VFD cables and Southwire makes VFD cables with each of these shield types. The shield types are: copper braid shield with aluminum foil (Copper Braid); A helically applied copper tape (Copper Tape); and a continuously corrugated welded aluminum used in MC cables (Aluminum Welded Armor). This application note will detail how to terminate each of these shield types.

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