Current Transformer

A current transformer is defined as "as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." This highlights the accuracy requirement of the current transformer but also important is the isolating function, which means no matter what the system voltage the secondary circuit need be insulated only for a low voltage.

The current transformer works on the principle of variable flux. In the "ideal" current transformer, secondary current would be exactly equal (when multiplied by the turns ratio) and opposite to the primary current. But, as in the voltage transformer, some of the primary current or the primary ampere-turns is utilized for magnetizing the core, thus leaving less than the actual primary ampere turns to be "transformed" into the secondary ampere-turns. This naturally introduces an error in the transformation. The error is classified into two-the current or ratio error and the phase error.

Current Transformers


  • The Current transformers are Tape wound / Abs Enclouser / Cast resin potted .
  • High quality C.R.G.O. silicon steel is used in the transformer.
  • High quality insulating paper is used to build up main insulation.
  • Smaller, Lighter and more accurate.
  • Turns Ratio and phase angle, with in guaranteed limits of standards.
  • Reliable, rugged and cost effective.
  • Customers specified design.
  • Standard CT Manufacturing Up to class 0.1


  • To step down line current to a value which is suitable for standard measuring instrument, relays etc.
  • To sense abnormalities in current and give current signals to protective relays to isolate the defective system. 3.3KV, Metering (0.5 to 3.0) Protection (5P- 10P)
  • Continuous thermal current (Ith): 1.2 times rated current.
  • Short time Pri. Current: Min 30 times rated primary current.
  • ISF: Less than 5.
  • Temp. Rise: Less than 30˚C.
  • Insulation Level: 0.66KV / 3KV
  • Class of Insulation: E OR B
  • Rated Burden: 2.5VA to 30VA& More
  • Type

    A) Measuring type.

    B) Protection type.

    C) Special Protection type. (PS Class)

    D) Combination of any of above with two or three cores.

  • Operating Voltage

    3.3kV, Maximum

  • Operating temperature

    -10°C to 50°C

  • Conforms to

    IS - 2705.

  • 3.3kV,

    Up to 2500 Amps.

  • Secondary Current

    5A & 1A (Others on Request)

  • Short time thermal current & its duration

    Up to 40kA for 1 second (Others on request)

  • Rated burden

    5, 10, 15, 20, 30VA (Others on request)

  • Frequency


  • Accuracy class

    Class 0.5,1 / protective 5P - 10P

  • Core

    Single as well as multi core CT available as per requirement


  • 3 CT Block for Trivector meters.
  • Accurate measuring for Metering / WATT / VAR.
  • Current Sensing, recording, monitoring and control.
  • Control panels & Drives.
  • Standard CT used as measuring standard for comparison.
  • Winding Temperature Indicator (WTI) for Power Transformers.

Information Requied With Inquiry:

  • Ratio.
  • Burden.
  • Accuracy class.
  • ID / Dimension
  • Bar / Wound Type.
  • Short time current rating if any.
  • Mounting Specifications.
  • Instrument Safety Factor (ISF)


  • Customer Specification accepted
  • Due to continue up gradation, above specifications are subject to change.
  • The Data presented is general information and should not be considered as a limited OR guaranteed.
  • 1 Amp. Secondary is also standard.
  • Customer specified designs include other secondary current, burden, accuracy and Size.
  • Wide range available for wound / Bar Primary and many type of windings possible.