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 Bore Size Transformer Type Overall Height Sensor Technology Overall Width Supply Voltage Input Current Overall Depth Output Current Minimum Temperature Maximum Temperature Dimensions For Use With
RS Stock No. 173-0217
BrandRS PRO
$7.675
Each (In a Box of 114)
units
200:1 - - - - - - 200A - - -55°C +130°C 38.1 x 15.9 x 38.1 mm -
RS Stock No. 124-3901
BrandRS PRO
$2.87
Each
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15:1 - - - - - - 15A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm -
RS Stock No. 173-0184
BrandRS PRO
$8.207
Each (In a Box of 98)
units
50:1 - - - - - - 50A - - -40°C +120°C 32 x 20.5 x 35 mm -
RS Stock No. 124-3883
BrandRS PRO
$10.30
Each
units
50:1 - - - - - - 50A - - -40°C +120°C 32 x 20.5 x 35 mm -
RS Stock No. 124-3893
BrandRS PRO
$8.44
Each
units
200:1 - - - - - - 200A - - -55°C +130°C 38.1 x 15.9 x 38.1 mm -
RS Stock No. 171-8841
BrandRS PRO
$98.89
Each
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1250:5 101 x 56mm Clip Fit 170mm - 130mm - 1250A 60mm 5 A -5°C +55°C 130 x 60 x 170 mm -
RS Stock No. 171-8750
BrandRS PRO
$21.54
Each
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50:5 21 x 10mm Clip Fit 65mm - 45mm - 50A 40mm 5 A -5°C +55°C 45 x 40 x 65 mm -
RS Stock No. 171-8835
BrandRS PRO
$98.89
Each
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1250:5 38 x 128mm Base Mounted 170mm - 99mm - 1250A 45mm 5 A -5°C +55°C 99 x 45 x 170 mm -
RS Stock No. 171-8792
BrandRS PRO
$23.58
Each
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500:5 40 x 11mm Clip Fit 78mm - 62mm - 500A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm -
RS Stock No. 171-8842
BrandRS PRO
$116.05
Each
units
1500:5 101 x 56mm Clip Fit 170mm - 130mm - 1500A 60mm 5 A -5°C +55°C 130 x 60 x 170 mm -
RS Stock No. 171-8820
BrandRS PRO
$58.72
Each
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1600:5 100 x 30mm Clip Fit 155mm - 140mm - 1600A 45mm 5 A -5°C +55°C 140 x 45 x 155 mm -
RS Stock No. 173-0215
BrandRS PRO
$3.035
Each (In a Box of 351)
units
5:1 - - - - - - 5A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm -
RS Stock No. 171-8793
BrandRS PRO
$33.92
Each
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400:1 40 x 11mm - 78mm - 62mm - - 40mm - - - 62 x 40 x 78 mm -
RS Stock No. 171-8804
BrandRS PRO
$46.92
Each
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1000:5 41 x 41mm Clip Fit 98mm - 74mm - 1000A 45mm 5 A -5°C +55°C 74 x 45 x 98 mm -
RS Stock No. 171-8757
BrandRS PRO
$28.87
Each
units
- - - - - - - - - - - - - -
RS Stock No. 171-8775
BrandRS PRO
$18.52
Each
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300:5 30 x 10mm Clip Fit 70mm - 50mm - 300A 31mm 5 A -5°C +55°C 50 x 31 x 70 mm -
RS Stock No. 171-8788
BrandRS PRO
$23.69
Each
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250:5 40 x 11mm Clip Fit 78mm - 62mm - 250A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm -
RS Stock No. 171-8816
BrandRS PRO
$68.86
Each
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1600:5 80 x 12mm Clip Fit 126mm - 104mm - 1600A 45mm 5 A -5°C +55°C 104 x 45 x 126 mm -
RS Stock No. 171-8829
BrandRS PRO
$40.90
Each
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250:5 35mm Base Mounted 87.5mm - 105mm - 250A 38mm 5 A - - 105 x 38 x 87.5 mm MCCB
RS Stock No. 171-8791
BrandRS PRO
$23.58
Each
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400:5 40 x 11mm Clip Fit 78mm - 62mm - 400A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm -