Electrical • Power Distribution • Transformers • Instrument Transformers

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  • ABB

    ABB manufactures a wide selection of instrument transformers, meant to accomplish three goals: to transform currents from high values to lower ones that are easier for relays and instruments to handle, to insulate metering circuits, and to provide possibilities of standardizing the instruments and relays to a few rated currents and voltages. The selection includes current transformers that are gas-insulated, oil-insulated, and magneto-optic, as well as single-phase voltage transformers for connecting phase and ground in networks with insulated or direct grounded neutral points. Still others are current/voltage transformers for voltages above 110 kV and coupling capacitors for power line carrier applications.

  • Amran Inc

    Amran Instrument Transformers offers a variety of instrument transformers, from current transformers to potential transformers. All of these products are made from grain-oriented silicon steel cores that have high accuracy and low loss. Cores are then annealed to relieve stress on the molecular structure and to ensure grain orientation in magnetic direction, and finally, insulated by tape, plastic caps, coating, etc.  CTs come in miniature, low voltage, and medium voltage selections with accuracy up to 0.1%, high linearity, and typical secondary current of 1 or 5A. PTs are offered in low and medium voltages up to 25kV, with thermal ratings up to 750 VA for single-phase metering class units.

  • Electro Industries/GaugeTech

    Electro Industries stocks a complete range of solid core and split core instrument transformers, as well as voltage transformers, for metering and protective relaying applications. Solid core CTs are designed for 50 to 400Hz frequencies and 600VAC insulation levels, accuracy from 1% to 3%, and burdens from 1.5 to 100. Split core CTs have the same frequency and insulation level ratings; they also offer a standard lead length of 36", burdens from 1 to 25, and 1% to 3% accuracy.

  • GE Digital Energy

    GE Digital Energy features a wide selection of instrument transformers. Several types of current transformers are available, such as the 600/720V indoor, 600V indoor/outdoor electrical utility style, 600V bushing type, and medium voltage IEEE/IEC indoor and outdoor CTs. Next are voltage transformers, which come in 600/720V models, some of which have thermal ratings (between 40 and 750VA) for use in low voltage switchgears, switchboards, panelboards, and electrical utilities for metering and instrumentation. Lastly, 5kV to 34.5kV class control power transformers are sold in single-phase or 3-phase indoor designs for use in medium voltage switchgears.

  • Hammond Manufacturing

    Hammond Manufacturing produces several types of instrument transformers, including the CT, EX, HX, VT, and PT Series. The CT Series features indoor, toroidal current transformers supplied with 24" insulated secondary leads and terminated with crimped ring connectors; these units are suitable for use with bare primary conductor circuits up to 600V, and offer current ratios from 50:5 up to 1,200:5. The EX, HX, and VT Series are grouped together, and are used with 150V full scale AC voltmeters to measure the voltage of 240, 480, and 600VAC systems. Each unit offers 1.2% accuracy and 50/60Hz operation. Finally, PT Series potential-small chassis mount transformers are used to measure the voltage of 120VAC systems with 5V full-scale AC voltmeters, with highly accurate windings (1%).

  • Arteche

    Arteche instrument transformers are made for both outdoor and indoor service. The former include oil-paper insulated, gas-insulated, inductive voltage, capacitative voltage, and many other types of transformers. By contrast, indoor transformers are divided by low and medium voltages; these include toroidal types for primary nominal currents up to 10A, rectangular window types up to 3A, and auxiliary transformers up to 200A, as well as window- and support-type units that provide 3.6kV to 24kV insulation voltage. Other related products include support resin-cast insulators, signal insulators, and wall bushings for insulation levels up to 36kV.

  • Flex-Core

    A variety of instrument transformers are available through Flex-Core. Among them are an array of current transformers like flexible split-core current transformers in 4" to 18" diameters, which features accuracy from 1% to 4%; relay and metering class transformers in four different models; and several series of 5KV and 15KV primary current transformers. Potential transformers are also available, including an assortment of 600V low voltage units, 3-phase open delta transformers, 5KV PTs (single- and 3-phase), and 15KV PTs.

  • Instrument Meter Specialties Inc

    A variety of instrument transformers are distributed by Instrument Meter Specialties. Among them are six current transformers for metering with 1 or 5 A AC secondary: 1.13" window Model 2, 1.25" Model 58, 1.56" Model 5, 2.06" Model 56, 2.5" Model 7, and 3" Model 76. Other current transformers for metering and relaying can be purchased, as well,such as the 2.5" window Model 7A and 3.25" Model 8. Taken as a whole, these products range from ratios of 50:5 to 6,000:5 and insulation classes up to 600V; furthermore, there are bus bar type CTs with ratios up to 3,000:5.

  • ITEC

    ITEC offers instrument transformers for a broad set of applications, including high voltage, oil-filled current transformers and quad sets of CTs for 765kV applications. Two featured products are the DDC-938 and SRW-911 rugged-molded, outdoor, dry-type CTs meant to slip over bushings in power transformers, circuit breakers, and potheads. Available in ratios ranging from 400:5 to 5,000:5, these CTs are also available as relay CTs with single-, dual-, or multi-ratio winding types for a full winding relay accuracy up to C800. The company also sells the RML 8.7kV class molded outdoor window CT for 1,000:5 through 12,000:5 ratios, and a variety of oil-filled voltage transformers, CT-VT metering units, and power potential units.

  • Ritz Instrument Transformers

    Ritz Instrument Transformers manufactures low and medium voltage transformers in addition to many related products. Low voltage units, which go up to 1.2kV, include CTs for measuring and protective purposes (e.g. wound current CT, auxiliary current CT, summation current CT, etc.), for measuring purposes alone (e.g. 3-phase CT, laboratory CT and voltage transformers), and for damping inductance devices against ferroresonance. Medium voltage instrument transformers include single- and double-pole VTs and indoor- and outdoor-application CTs. Lastly, Ritz produces power transformers with glass fiber-reinforced vacuum technology for ratings up to 20MVA and 36kV voltage class in power distribution, traction supply systems, rectifier drives, and myriad other applications.

  • Trench Group

    Trench carries two types of instrument transformers. The first are IOSK oil-insulated current transformers, available in voltage ratings from 72.5kV to 550kV. These units support primary currents up to 5,000 A, and meet all IEC and IEEE/ANSI metering and protection classes; special core class ratings TPS, TPX, TPY, and TPZ are also available. Moreover, the company distributes SF6 CTs in a voltage range from 72.5kV up to 800kV. Designed in accordance with main international standards for design, test, and construction, these products are explosion-proof due to an SF6 gas insulation system and rupture disk.


    Areva carries a wide selection of instrument transformers from low to high voltage designs. Low voltage products (up to 600V) include outdoor slip-over current transformers, internal bushing CTs, split core CTs, and generator CTs. Medium voltage units (15kV to 69kV) feature outdoor wound- and bar-type CTs, outdoor and indoor voltage transformers, indoor CTs, and more. High voltage transformers (69kV to 765kV) include coupling capacitor VTs, standard CTs and VTs, combined metering units, and breaker capacitors. Also available are SF-6-filled CTs and VTs for very high thermal and mechanical current ratings, in excess of 80kA/second depending on design.

  • Agile Magnetics (div of Regional Manufacturing Specialists)

    Agile Magnetics manufactures a variety of custom transformers including a full line of instrument transformers designed and built to change the line voltage to meet the needs the customer has for control voltages. Instrument transformers designed and manufactured by Agile Magnetics are built to UL / CUL / VDE and CE, with UL and CUL markings when required. Agile Magnetics is an ISO 9001 compliant manufacturer.

  • Square D

    For measurement and control of generation, transmission, and distribution equipment, Schneider Electric features many types of instrument transformers in different voltage classes, including low- and medium-voltage current and voltage transformers. Common characteristics include molded thermo-plastic cases, low energy loss grain-oriented silicon steel, and permanent polarity marks molded into the case, with window sizes from 1.13" to 8.13". Standards met include ANSI C57.13 and CSA C13, as well as UL and cUL recognition per Classification XODW2, File No. E100570.