Current Transformers

Current transformers or (CT’s) are instruments that are used to transform the current from a high current into a lower current so that the power can then be used for measuring and controlling. The transformers consist of a core, a primary and a secondary winding.RS Components offer an extensive range of highly accurate CT’s in various transformer types, current ratings, CT ratio supply voltages and mounting types to suit every application. Supplied by industry-leading brands including Siemens, Murata Power Solutions LEM and of course RS PRO.

How does a current transformer work?

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.

Types of current transformer

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.

Where would I use a current transformer?

CT's are used in a wide range of industrial and commercial measurement applications. Some of the most common are:Generating stationsElectrical substationsCommercial electric power distributionElectrical panels


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Description Price Current Ratio Bore Size Transformer Type Sensor Technology Supply Voltage Input Current Output Current Overall Height Minimum Temperature Overall Width Maximum Temperature Overall Depth Dimensions For Use With
RS Stock No. 510-9152
Mfr. Part No.7KT1201
BrandSiemens
£166.02
Each
Units
- 13mm Straight Through - - - - - - - - - - -
RS Stock No. 772-1212
Mfr. Part No.5SV8700-0KK
BrandSiemens
£87.13
Each
Units
- 20mm Toroidal Ring - - - - 34mm -10°C - +50°C - - -
RS Stock No. 772-1221
Mfr. Part No.5SV8702-0KK
BrandSiemens
£106.56
Each
Units
- 35mm Toroidal Ring - - - - 79mm -10°C 100mm +50°C 58.8mm - -
RS Stock No. 123-9539
Mfr. Part No.7KT1200
BrandSiemens
£178.97
Each
Units
60:5 13mm Straight Through - - 60A 5 A - - - - - 105 x 71 x 90 mm -
RS Stock No. 123-9540
Mfr. Part No.7KT1202
BrandSiemens
£167.20
Each
Units
150:5 13mm Straight Through - - 150A 5 A - - - - - 105 x 71 x 90 mm -
RS Stock No. 123-9532
Mfr. Part No.4NC5328-2CE20
BrandSiemens
£70.96
Each
Units
750:5 36mm Window - - 750A 5 A - -10°C - 55°C - 82.5 x 80 x 98 mm Measuring Devices
RS Stock No. 123-9519
Mfr. Part No.4NC5223-0CE20
BrandSiemens
£59.22
Each
Units
250:1 28mm Window - - 250A 1 A - -10°C - 55°C - 80 x 64 x 85.5 mm Measuring Devices
RS Stock No. 123-9505
Mfr. Part No.4NC5113-0BC20
BrandSiemens
£76.90
Each
Units
60:1 17.5mm Window - - 60A 1 A - -10°C - 55°C - 74.5 x 48 x 80 mm Measuring Devices
RS Stock No. 123-9523
Mfr. Part No.4NC5225-0CE20
BrandSiemens
£66.84
Each
Units
400:1 28mm Window - - 400A 1 A - -10°C - 55°C - 80 x 64 x 85.5 mm Measuring Devices
RS Stock No. 123-9507
Mfr. Part No.4NC5115-0BC20
BrandSiemens
£68.12
Each
Units
75:1 17.5mm Window - - 75A 1 A - -10°C - 55°C - 74.5 x 48 x 80 mm Measuring Devices
RS Stock No. 175-6215
Mfr. Part No.4NC5438-2DL21
BrandSiemens
£98.22
Each
Units
2000:5 - Window - - 2000A 5 A 84.1mm -30°C 112mm +55°C 127.5mm 112 x 127.5 x 84.1 mm Sentron Power Monitoring Devices
RS Stock No. 175-6149
Mfr. Part No.4NC5122-2FC21
BrandSiemens
£50.14
Each
Units
200:5 - Window - - 200A 5 A 65.6mm -30°C 60mm +55°C 75.3mm 60 x 75.3 x 65.6 mm Sentron Power Monitoring Devices
RS Stock No. 175-6216
Mfr. Part No.4NC5440-0CJ21
BrandSiemens
£106.39
Each
Units
2500:1 - Window - - 2500A 1 A 84.1mm -30°C 112mm +55°C 127.5mm 112 x 127.5 x 84.1 mm Sentron Power Monitoring Devices
RS Stock No. 175-6150
Mfr. Part No.4NC5123-0CE21
BrandSiemens
£47.20
Each
Units
250:1 - Window - - 250A 1 A 65.6mm -30°C 60mm +55°C 75.3mm 60 x 75.3 x 65.6 mm Sentron Power Monitoring Devices
RS Stock No. 175-6122
Mfr. Part No.3UL2302-1A
BrandSiemens
£110.02
Each
Units
40:1 - Toroidal Ring - - 40A 85 A 64mm -25°C 70mm +60°C 75.5mm 70 x 75.5 x 64 mm Fault Current Monitoring
RS Stock No. 175-6137
Mfr. Part No.4NC5117-0DA21
BrandSiemens
£50.14
Each
Units
200:1 20mm Window - - 200A 1 A 65.6mm -30°C 60mm +55°C 75.3mm 60 x 75.3 x 65.6 mm Sentron Power Monitoring Devices
RS Stock No. 175-6193
Mfr. Part No.4NC5330-2DE21
BrandSiemens
£50.14
Each
Units
750:5 - Window - - 750A 5 A 84.1mm -30°C 82.5mm +55°C 98mm 82.5 x 98 x 84.1 mm Sentron Power Monitoring Devices
RS Stock No. 175-6217
Mfr. Part No.4NC5440-2CJ21
BrandSiemens
£94.80
Each
Units
2500:5 - Window - - 2500A 5 A 84.1mm -30°C 112mm +55°C 127.5mm 112 x 127.5 x 84.1 mm Sentron Power Monitoring Devices
RS Stock No. 175-6151
Mfr. Part No.4NC5123-0DE21
BrandSiemens
£50.14
Each
Units
250:1 - Window - - 250A 1 A 65.6mm -30°C 60mm +55°C 75.3mm 60 x 75.3 x 65.6 mm Sentron Power Monitoring Devices
RS Stock No. 175-6123
Mfr. Part No.3UL2303-1A
BrandSiemens
£117.98
Each
Units
40:1 - Toroidal Ring - - 40A 150 A 64mm -25°C 92mm +60°C 98mm 92 x 98 x 64 mm Fault Current Monitoring