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. 886-2109
Mfr. Part No.XW01-065081S000000
SGD29.24
Each
units
10:5 - Base Mounted - - - - - - - 62 x 40 x 78 mm - Surface Mount Omega XMER
RS Stock No. 331-468
Mfr. Part No.CT132M120/5-2.5/1
BrandHOBUT
SGD23.43
Each
units
120:5 21mm DIN Rail Mounted 65mm 45mm 30mm - - -30°C +85°C - - - -
RS Stock No. 331-430
Mfr. Part No.CT132M150/5-2.5/1
BrandHOBUT
SGD24.21
Each
units
150:5 21mm DIN Rail Mounted 65mm 45mm 30mm - - -30°C +85°C - - - -
RS Stock No. 533-0643
Mfr. Part No.CTSCM40-200/5
BrandHOBUT
SGD80.92
Each
units
200:5 - Clip Fit 104.5mm 116mm 35.5mm - - -30°C +80°C - - - -
RS Stock No. 913-9731
Mfr. Part No.METSECT5CC005
SGD76.15
Each
units
50:5 21mm Toroidal Ring - - - - - -25°C +60°C 65 x 44 x 30 mm - DIN Rail -
RS Stock No. 397-9117
Mfr. Part No.BZCT035
SGD55.73
Each
units
- 35mm - 74mm 64mm 40mm - - -20°C +60°C - Broyce Type A Earth Leakage Relays Surface Mount BZCT
RS Stock No. 399-7244
Mfr. Part No.ASM-010
SGD7.18
Each
units
- - - - - - 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
SGD18.52
Each
units
- 12mm Split Core - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders - -
RS Stock No. 106-8534
Mfr. Part No.56050C
SGD2.38
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. 331-597
Mfr. Part No.CT132M40/5-1/3
BrandHOBUT
SGD21.60
Each
units
40:5 21mm DIN Rail Mounted 65mm 45mm 30mm - - -30°C +85°C - - - -
RS Stock No. 331-474
Mfr. Part No.CT132M50/5-1/1
BrandHOBUT
SGD21.60
Each
units
50:5 21mm DIN Rail Mounted 65mm 45mm 30mm - - -30°C +85°C - - - -
RS Stock No. 715-7068
Mfr. Part No.56050C
SGD2.44
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
SGD62.24
Each
units
- 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. 914-5294
Mfr. Part No.CTSCMWH60/0.333V
BrandHOBUT
SGD33.30
Each
units
- 10mm Split Core - - - 60A 333 mV -15°C +50°C 28.7 x 26.4 x 41.7 mm Multi Function Meter Cable -
RS Stock No. 832-9857
Mfr. Part No.L01-8001
BrandAlttec
SGD20.20
Each
units
50:5 21.5mm Clip Fit 65mm 45mm 30mm - - - +40°C 65 x 45 x 67 mm - - -
RS Stock No. 441-4920
Mfr. Part No.BZCT120
SGD168.07
Each
units
- 120mm - 170mm 155mm 40mm - - -20°C +60°C - Broyce Type A Earth Leakage Relays Surface Mount BZCT
RS Stock No. 715-7071
Mfr. Part No.56T200C
SGD2.44
Each
units
- - - - - - 10A - -40°C +85°C 16.79 x 8.89 x 20.19 mm - Through Hole -
RS Stock No. 106-8535
Mfr. Part No.56T200C
SGD2.38
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. 881-7910
Mfr. Part No.CTPROXT100
BrandABB
SGD32.44
Each
units
- 18mm - - - - - - -5°C +50°C 45 x 96 x 69 mm - BusBar, DIN Rail CT PRO XT
RS Stock No. 775-2701
Mfr. Part No.CTSCMICRO19-100/5-T-S
BrandHOBUT
SGD76.77
Each
units
- - - 78mm 58mm 49mm - - -30°C 55°C - - - -
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