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. 751-1642
Mfr. Part No.93490 P1
$42.52
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units
- - - - - - 800A - -20°C +70°C 102 (Dia.) x 20 mm - Stand Alone -
RS Stock No. 537-4491
Mfr. Part No.AC-1010
$6.484
Each (In a Pack of 5)
units
- - - - - - 10A - -40°C +120°C 23.8 x 23.8 x 11.12 mm - PCB Mount -
RS Stock No. 832-9851
Mfr. Part No.L01-8002
BrandAlttec
$25.11
Each
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100:1 21.5mm Clip Fit 65mm 45mm 30mm - - - +40°C 65 x 45 x 67 mm - - -
RS Stock No. 250-0142
Mfr. Part No.TRA12UN100
BrandCarel
$19.10
Each
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- - - 47mm 58mm 33mm - - - - - 12/24Vac controllers Surface Mount -
RS Stock No. 715-7077
Mfr. Part No.56T100C
$2.73
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- - - - - - 10A - -40°C +85°C 16.79 x 8.89 x 20.19 mm - Through Hole -
RS Stock No. 124-3893
BrandRS PRO
$10.55
Each
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- - - - - - 75 → 200A - -55°C +130°C 38.1 x 15.9 x 38.1 mm - PCB Mount -
RS Stock No. 533-0637
Mfr. Part No.CTSCM40-100/5
BrandHOBUT
$94.13
Each
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100:5 - Clip Fit 104.5mm 116mm 35.5mm - - -30°C +80°C - - - -
RS Stock No. 399-7244
Mfr. Part No.ASM-010
$8.48
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- - - - - - 10A - -40°C +120°C 20.4 x 17.2 x 9.53 mm - PCB Mount -
RS Stock No. 819-9779
Mfr. Part No.90AS
BrandEfergy
$24.45
Each
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- 12mm Split Core - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders - -
RS Stock No. 173-0217
BrandRS PRO
$9.681
Each (In a Box of 114)
units
- - - - - - 75 → 200A - -55°C +130°C 38.1 x 15.9 x 38.1 mm - PCB Mount -
RS Stock No. 173-0041
BrandRS PRO
$2.091
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. 124-3879
BrandRS PRO
$2.52
Each
units
- - - - - - 15A - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 106-8537
Mfr. Part No.56T100C
$2.662
Each (In a Tube of 25)
units
- - - - - - 10A - -40°C +85°C 16.79 x 8.89 x 20.19 mm - Through Hole -
RS Stock No. 886-2099
Mfr. Part No.XW01-045081S000000
$35.85
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5:5 - Base Mounted - - - - - - - 62 x 40 x 78 mm - Surface Mount Omega XMER
RS Stock No. 537-4485
Mfr. Part No.AC-1005
$6.268
Each (In a Pack of 5)
units
- - - - - - 5A - -40°C +120°C 23.8 x 23.8 x 11.12 mm - PCB Mount -
RS Stock No. 715-7061
Mfr. Part No.56100C
$2.73
Each
units
- - - - - - 10A - -40°C +85°C 16.79 x 8.89 x 20.19 mm - Through Hole -
RS Stock No. 914-5301
Mfr. Part No.CTSCMWH500/0.333V
BrandHOBUT
$75.20
Each
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- 35mm Split Core - - - 500A 333 mV -15°C +50°C 51.2 x 51.2 x 83.5 mm Multi Function Meter Cable -
RS Stock No. 173-0070
Mfr. Part No.AX-0500
$5.174
Each (In a Box of 250)
units
- - - - - - 5A - -40°C +120°C 12.7 x 17 x 9.53 mm - Through Hole -
RS Stock No. 745-7995
Mfr. Part No.TRA2400001
BrandCarel
$22.87
Each
units
- - - - - - - - -10°C +50°C - 12/24Vac controllers Surface Mount -
RS Stock No. 351-910
Mfr. Part No.MI100
$104.64
Each
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- - - 67.5mm 95mm 20mm 10 → 100A - -20°C +60°C - - - -
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