Current Transformer

A current transformer is a static device which generate an alternating current in its secondary coil which is proportional to the alternating current in its primary coil. A current transformer (CT) is used where the current is too high to measure directly, or the voltage in the primary circuit is too high, so the galvanic isolation between primary and secondary is important for safety or technical reasons.

Applications of Current Transformer

  • Metering (electrical energy meters)
  • AC Voltage measurements
  • Sensing Overload Current
  • Ground fault detection
  • Household electrical equipment
  • Industrial apparatuses
  • Electrical testing equipment and relay protection
  • Commercial metering
  • Current sensing, recording, monitoring & control
  • Control panels (VCB ,AMF,APFC ,MCC ,PCC & Relay Panels) and Drives
  • Standard CT for laboratory purposes
  • Earth fault protection/Differential protection/Bus-bar protection Systems
  • Bushing type, oil-immersed CT in power transformer

Features of ZMCT103C Micro Precision Current Transformers

  • low price
  • small size ( 18.3mm x17 mm) and lightweight
  • Easy PCB mounting
  • Good consistency
  • widely acclaimed

Types of current transformer depend on Cunstruction

Ring type: Ring type current Transformer is constructed of an iron toroid, which forms the magnetic core of the current transformer, and secondary turns are wound with copper wire. The doughnut fits over the primary conductor, which constitutes one primary turn. Ring type current transformer do not contain a primary winding. Instead, the power line that carries the alternating current flowing in the circuit is threaded through a window or hole in the Ring type CT. Centre hole can be supplied ‘stepped’ to enable secure mounting on busbars.

Wound type: This has a wound primary of four or more turns. These are more accurate for primary currents less than around 500A.

Split core type: Can open the core and place around the conductor. Good for existing conductor which you cannot break to thread a conventional C.T. onto.

Bushing type: This is typically used for monitoring current in high-voltage conductors. It is integrated into insulator bushing to achieve the high voltage insulation required between primary and core.

Types of current transformer depend on Cunstruction


There are two type of current transformer.

  • Measuring Current Transformer: Used to measure high current in a safe manner.generally class 0.1,0.2,1.0.
  • Protection current transformer: used to protect the circuit through protective relays.generally having class 5P10,10P10,5P20…etc.

Measuring current transformers are constructed to feed on other low voltage apparatus such as measuring instruments,relaysrwatt-hour meters (kW meter) and these type of current eransformers are maInly used 0.5 and 1 class to transfer the current from highest rated current to ra ted secondary current.

Pratection current transformers are constructed to feed the protectian relay.These type of current tra n sfa rmers are mainly used 5 P.(Customer supplIed when required.)