Energypac introduced its indigenously developed Instrument Transformers in 1995. Since then Energypac is the only manufacturer of instrument transformers in Bangladesh. Energypac manufactures outdoor/indoor, oil cooled/cast resin Current Transformers (CT) ranging from 11 kV to 230 kV. Our modern manufacturing plant is equipped with full range of testing equipment, plant and machinery to manufacture these transformers. We have supplied hundreds of these transformers to different customers in home and abroad which are working satisfactorily under different service conditions at sites. Our Instrument Transformers are manufactured in accordance with latest IEC/ANSI Standards.

Current Transformers (CT): Direct measurement of current in high voltage system is not possible because of insulation problem of measuring instruments. It is also not possible to use current flowing through the system directly for protection purpose due to its high value and high insulation problem.

Basic functions of current transformers are:

Energypac manufactures current transformers (CT) in bout Live Tank and Dead Tank design types. CT can be designed for Single or Multi ratio. The ratio selection can be achieved by providing two or four sections or primary for series/parallel connection, the current ratio shall be in proportion of 1:2:4. The advantage of this type of ratio is that output from each secondary remains constant for any selected ratio.

High permeability CRGO silicon steel is used as core material. Toroidal cores from continuous strips are made at our works and annealed in controlled atmosphere to achieve best quality secondary cores. Secondary winding is done automatically and distributed equally on the periphery of the core to minimize leakage reactance. Primary winding is of braided electrolytic copper conductors with double cotton covering. Varnished fiber glass sleeve is provided as an additional insulation on this conductor. High quality crepe insulating paper is used to build up main insulation of the CT. brown/white glazed porcelain bushing with different shade profiles to suit different pollution conditions are used. These bushings are hollow cylindrical type conforming to bushings IEC 815/15 5621. Top tank (which also acts as oil expansion chamber) of the CT having current less than 1200 Amperes are made of MS sheet. Stainless sheet tanks are used for CTs with primary current of 1200A and above.

Epoxy resin cast CT is manufactured in compliance with IEC, ANSI, VDE, BS standards and as per customer's specification. The windings are provided over high quality cold rolled grain oriented steel which is annealed. The material has got low loss and high permeability. LT winding is designed as multi-layer winding. LT winding is wound on the core with additional insulation between adjacent layers. HT winding is designed in such a way that the mechanical stresses due to thermal dilation, in case of short circuit currents are not transmitted to the main insulation of the transformer. The conductors used for windings are made of electrical grade electrolytic copper. Conductors used for secondary windings are insulated with high quality, synthetic resin based insulation varnish. Insulation of these transformers is epoxy-resin compound of superior dielectric and mechanical properties.

Potential Transformers (PT): Direct measurement of voltage in high voltage system is not possible because of insulation problem of measuring instruments. It is also not possible to use direct voltage for the system protection purpose due to its high value and high insulation problem of protective relays. Therefore, Voltage Transformers or Potential Transformers (PT) are used to step-down the high system voltage to low standard value accurately in proportion to their ratio.

Basic functions of potential transformers are:

Single phase electromagnetic PT is manufactured in two types:

Three phase PTs are of star/start connected or star/open delta connected (Residual Voltage Transformer) type.

Energypac ensure quality test facility as to IEC-76, VDE 0537, ANSI C 57.12 and BS 171 and every transformer are dispatched from the factory after being tested properly and passing quality requirements.

Potential Transformer consists of

Copper enameled wire is used for winding. Primary is wound with multilayer and graded insulation. Secondary is separately wound and inserted in the primary winding as per the requirement. Winding and tapping of PT is done in dust-free atmosphere. CRGO silicon steel is used for building up electromagnetic core. Shell type construction is used to minimize leakage reactance. Bottom tank and oil expansion chamber are made of MS sheet. Brown/white glazed porcelain bushing with different shed profiles to suit different pollution condition is used. These bushings are hollow cylindrical type conforming to IEC 815/IS 5621. High quality electrical grade Kraft paper and crepe paper is used for insulating primary and secondary of PT.

Epoxy resin cast PT is manufactured in compliance with IEC, ANSI, VDE, BS standards and as per customer's specification. Cores used in PT are of high quality cold rolled grain oriented steel which is annealed. HT and LT windings are designed as multi layer windings. The low voltage winding is wound on insulated bobbin. Conductors used for windings are made of electrical grade electrolytic copper. The conductors are insulated with high quality, synthetic resin based, insulating varnish. The whole encapsulation forms hermetically reeled system with primary and secondary terminals. PTs are available at single, double and three phase versions and they are of indoor and outdoor types.