Current Transformers

Current transformers (CT) are devices that are used to transform the current from a high current into a lower current so that the power can then be measured and controlled. The transformers consist of a core, a primary and a secondary winding. When an alternating current flows through the primary winding, a magnetic flux is created which then induces an alternating current in the secondary winding. This alternating current is proportional to the current in its primary. Current transformers are also known as a "step-down transformers". Once the current has been reduced it can be safely monitored and measured using an ammeter.


Current transformers can perform circuit control and perform roles for safety protection and current limiting.


Current transformers are found in:


  • Generating stations,

  • Electrical substations

  • Commercial electric power distribution.

Types of Current Transformers


Toroidal Current Transformer - These transformers are shaped like a doughnut they do not contain a primary winding. Instead, the line that carries the current flowing in the network is threaded through a window or hole in the toroidal transformer. Toroidal transformers offer high efficiency with minimal excess noise and little excess leakage inductance.


Wound Current Transformer - The transformers primary winding is physically connected in series with the conductor that carries the measured current flowing in the circuit. The magnitude of the secondary current is dependent on the turns ratio of the transformer.


Bar-type Current Transformer – This type of current transformer uses the actual cable or bus-bar of the main circuit as the primary winding, which is equivalent to a single turn. They are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device.


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Description Price Current Ratio Inner Diameter Transformer Type Overall Height Overall Width Overall Depth Input Current Output Current Minimum Temperature Maximum Temperature Dimensions For Use With Mounting Type Series
RS Stock No. 124-3897
BrandRS PRO
€3.55
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units
- - - - - - 50A - -40°C +85°C 19 x 11.5 x 21.5 mm - PCB Mount -
RS Stock No. 173-0236
BrandRS PRO
€1.588
Each (In a Box of 351)
units
- - - - - - 15A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0181
BrandRS PRO
€2.939
Each (In a Box of 351)
units
- - - - - - 1 → 10A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3882
BrandRS PRO
€3.58
Each
units
- - - - - - 1 → 10A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3879
BrandRS PRO
€1.19
Each
units
- - - - - - 15A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3901
BrandRS PRO
€1.51
Each
units
- - - - - - 15A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0041
BrandRS PRO
€0.973
Each (In a Box of 351)
units
- - - - - - 15A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 171-8778
BrandRS PRO
€12.71
Each
units
500:5 30 x 10mm Clip Fit 70mm 50mm 31mm 500A 5 A -5°C +55°C 50 x 31 x 70 mm - Surface Mount -
RS Stock No. 171-8814
BrandRS PRO
€32.14
Each
units
1250:5 80 x 12mm Clip Fit 126mm 104mm 45mm 1.25kA 5 A -5°C +55°C 104 x 45 x 126 mm - Surface Mount -
RS Stock No. 171-8779
BrandRS PRO
€13.87
Each
units
600:5 30 x 10mm Clip Fit 70mm 50mm 31mm 600A 5 A -5°C +55°C 50 x 31 x 70 mm - Surface Mount -
RS Stock No. 171-8835
BrandRS PRO
€60.03
Each
units
1250:5 38 x 128mm Base Mounted 170mm 99mm 45mm 1.25kA 5 A -5°C +55°C 99 x 45 x 170 mm - Surface Mount -
RS Stock No. 171-8817
BrandRS PRO
€37.97
Each
units
2000:5 80 x 12mm Clip Fit 126mm 104mm 45mm 2kA 5 A -5°C +55°C 104 x 45 x 126 mm - Surface Mount -
RS Stock No. 171-8851
BrandRS PRO
€45.28
Each
units
400:5 33 x 23mm Base Mounted 106mm 93mm 40mm 400A 5 A +20°C +70°C 93 x 40 x 106 mm - Surface Mount -
RS Stock No. 171-8831
BrandRS PRO
€29.21
Each
units
300:5 45mm Base Mounted 102.5mm 141mm 38mm 300A 5 A - - 141 x 38 x 102.5 mm MCCB Surface Mount -
RS Stock No. 171-8815
BrandRS PRO
€33.59
Each
units
1500:5 80 x 12mm Clip Fit 126mm 104mm 45mm 1.5kA 5 A -5°C +55°C 104 x 45 x 126 mm - Surface Mount -
RS Stock No. 171-8824
BrandRS PRO
€24.83
Each
units
100:5 35mm Base Mounted 87.5mm 105mm 38mm 100A 5 A - - 105 x 38 x 87.5 mm MCCB Surface Mount -
RS Stock No. 171-8788
BrandRS PRO
€13.73
Each
units
250:5 40 x 11mm Clip Fit 78mm 62mm 40mm 250A 5 A -5°C +55°C 62 x 40 x 78 mm - Surface Mount -
RS Stock No. 173-0216
BrandRS PRO
€3.104
Each (In a Box of 351)
units
- - - - - - 7.5A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0198
BrandRS PRO
€3.797
Each (In a Box of 176)
units
- - - - - - 30 → 75A - -55°C +130°C 30.2 x 14.3 x 30.2 mm - PCB Mount -
RS Stock No. 171-8844
BrandRS PRO
€75.96
Each
units
2000:5 101 x 56mm Clip Fit 170mm 130mm 60mm 2kA 5 A -5°C +55°C 130 x 60 x 170 mm - Surface Mount -
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