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Single Phase Transformers Isolation transformers should be used on all systems which require grounding of the load. Rex single phase distribution transformers are ideal for supplying auxiliary lighting circuits from 600 V and lower supplies, and electric heating equipment. Three Phase Transformers Designed for indoor installation in hotels, schools, factories and industrial and commercial buildings where a reliable power source is required for lighting and other low voltage equipment and machinery. Three Phase Auto Transformers Auto transformers are an economical and compact means of connecting electrical equipment to a power supply of a different voltage. Part of the winding is common to both primary and secondary circuits so there is no isolation between the two. This may not be acceptable on some power systems which do not have a grounded neutral on the secondary side of the main power transformer. Typical applications include loads of industrial machinery, electric heating, air conditioners, etc. Encapsulated Transformers Standard dry type ventilated transformers are cooled by circulating the surrounding air through its windings. For trouble free operation and long life expectancy this ventilating air must be reasonably free of dust, moisture or other damaging corrosive fumes. For this reason, standard Dry Type ventilated transformers are normally installed in suitable, indoor locations where they are protected from damaging elements. Some specifications require installation of transformers in hazardous surroundings where the above mentioned conditions can not be met. Resin encapsulated transformers are designed for such surroundings.
Energy Efficient Transformers As energy prices rise it is desirable to reduce the operating costs of electrical systems. Transformers manufactured with temperature rises of 80° C or 115° C are designed with lower than normal conductor and total losses which results in greater life expectancy, lower operating costs and significant overload capabilities. The losses of a transformer are a very small percentage of the total power which flows through it. However all transformers have losses which appear in the form of heat. The total losses are the sum of the core loss and the load loss. Core loss: losses that are mainly caused by the resistance of the iron core to the magnetic flux magnetizing it. These losses can be reduced by lowering the flux density, using higher grade steel and careful assembly procedures. Load loss: losses that are caused primarily by the resistance of the winding conductors to the current which flows through them. These losses can be reduced by lowering the resistance of the windings and by lowering the temperature rise of the transformer. Rex energy efficient transformers are designed with reduced core losses and reduced operating temperatures (Temp. rise). Each transformer operating at a temperature rise of 115° C. or 80° C. will have approximately 20% and 35% lower losses respectively compared with conventional 150° C. rise units. An additional benefit of Rex energy efficient trans- formers is enhanced overload capability. Transformers rated at 115° C. or 80° C. temperature rises can be operated at as a 150° C. unit and yield an overload capability of 15% or 30% without reducing the life expectancy or service reliability.
Electrostatically Shielded Transformers Electrostatically (faraday) shielded transformers are designed to protect sensitive electrical and electronic devices and systems from high frequency voltages (electrical noise) or transients that occur due to switching and loading on distribution lines. Electrical noise and transients are classified two
ways. K-Factor Rated Transformers A K-factor rating applied to a transformer is an index of the transformers ability to supply harmonic content in its load current while operating within its temperature limits. For dry type transformers a "K-factor" calculation is made to determine the amount of harmonic content present in a power system. K-rated transformers are sized to handle 100% of the fundamental 60 Hz load plus the non-linear load specified. The neutral of the transformer is sized at 200% of the current rating of the phase connections. Drive Isolation Transformers Rex Manufacturing drive isolation transformers are specifically designed to meet the requirements of AC and DC variable speed drives or rectifier outputs. Rex DIT transformers are manufactured and rated to match standard motor horsepower and voltage ratings. |
