| Mineral-insulated Copper-clad Cable |
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Information AboutMineral-insulated Copper-clad Cable |
| CATEGORIES ABOUT MINERAL-INSULATED COPPER-CLAD CABLE | |
| power cables | |
| passive fire protection | |
| electrical wiring | |
| electric heating | |
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Mineral Insulated Copper Clad cable, often abbreviated to MICC (alternatively '''Mineral Insulated Metal Sheathed''' or '''MIMS''') and colloquially known as '''pyro''', is a type of Electrical Cable . It is characterised by using Magnesium Oxide , an Inorganic Mineral , to provide electrical Insulation . It consists of a Copper Tube , circular in Cross Section , packed with magnesium oxide ( Magnesia ), in which solid copper current-carrying cores are embedded. The number of cores may be from one to seven or more although the most common configurations are two-core (for Single Phase power circuits) and three- and four-core (for control and Three Phase power circuits). In most applications the copper cladding is connected to Earth . This serves as the circuit protective conductor, provides screening against Electromagnetic Radiation and earths any tool that inadvertantly penetrates the cable (which should ensure a Short Circuit and therefore rapid disconnection when the live conductors are hit). Where electromagnetic interference is a particular concern, cables with conductors in a Twisted Configuration are available. There may be an overall PVC coating which is usually white, red or orange. This is used for Aesthetic or circuit identification reasons - red and orange are frequently used to distinguish Fire Alarm circuits. It may also be required for safety reasons where a raised voltage on the copper cladding under fault conditions might be particularly dangerous e.g. in Swimming Pool s, and in some situations for Corrosion protection of the copper. MICC cable has a number of significant advantages:
It is better able to radiate heat and operate at higher temperatures as compared to PVC-insulated cable, and therefore a smaller conductor cross-sectional area (CSA) is required for a given current carrying capacity. For example, a 1.5 mm² MICC cable is comparable with a 2.5 mm² PVC-insulated cable in terms of current carrying capacity. This means that the overall Diameter of the cable is smaller as compared to other cable types. It is commonly used in applications where these properties are particularly desirable, such as:
Due to Oxidation , the copper cladding darkens with age and MICC is therefore often used in Historic buildings such as Castle s where it blends in with stonework. MICC is not suitable for use where it will be subject to Vibration or flexing, e.g. for direct connection to heavy or movable machinery, as this will quickly crack the cladding and cores, leading to failure. Installation of MICC requires a certain amount of skill. Care must be taken not to flex or bend it more than necessary as this will cause cracks in the cladding and cores. Minimum Bend Radii must be observed and the cable must be supported at regular intervals. The magnesium oxide insulation is Hygroscopic and MICC cable must therefore be kept away from sources of Moisture , including wet Cement and Plaster , until it has been properly terminated. Termination involves carefully stripping back the copper cladding and attaching a compression gland to provide a sound electrical and mechanical connection. An Epoxy Resin is then used to provide a watertight seal. If this termination process is not carried out properly then the magnesium oxide will over time absorb Atmospheric Moisture and lose its insulating properties. Installation of MICC is therefore a skill-intensive, and therefore costly task. In recent years it has been superseded in many applications with PTFE , Silicone or other proprietary Polymer -insulated cables which provide similar properties in terms of fire resistance and do not require any particular skill to install. MICC is however still used in applications which are particularly demanding in terms of performance or aesthetics. TYPICALLY AVAILABLE SPECIFICATIONS
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