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. 715-7970
Mfr. Part No.2308027
£178.90
Each
Units
100:1 32mm - - 20 → 30 V dc 100A 4 → 20 mA 70mm -40°C 90mm +65°C 33.8mm - -
RS Stock No. 820-0431
Mfr. Part No.2904921
£275.09
Each
Units
4000:1 8.3mm - - 24 V dc 4000A 0 → 1 A 70.4mm -30°C 22.5mm +80°C 85mm - -
RS Stock No. 820-0435
Mfr. Part No.2904922
£275.59
Each
Units
4000:1 8.3mm - - 24 V dc 4000A 0 → 1 A 70.4mm -30°C 22.5mm +80°C 85mm - -
RS Stock No. 302-6077
Mfr. Part No.2814359
£102.62
Each
Units
5:1 - - - - 5A 0 → 20 mA 99mm -25°C 22.5mm +60°C 114.5mm - -
RS Stock No. 337-2746
Mfr. Part No.2814728
£200.90
Each
Units
55:1 - - - 20 → 30 V dc 55A 0 → 20 mA 99mm -20°C 22.5mm +60°C 114.5mm - -
RS Stock No. 820-0444
Mfr. Part No.2904923
£276.05
Each
Units
4000:1 8.3mm - - 24 V dc 4000A 0 → 1 A 70.4mm -30°C 22.5mm +80°C 85mm - -
RS Stock No. 801-6283
Mfr. Part No.2308043
£187.01
Each
Units
300:1 32mm - - 24 V dc 300A 4 → 20 mA 33.8mm -40°C 90mm +65°C 85mm - -
RS Stock No. 715-7989
Mfr. Part No.2308030
£178.90
Each
Units
200:1 32mm - - 20 → 30 V dc 200A 4 → 20 mA 70mm -40°C 90mm +65°C 33.8mm - -
RS Stock No. 801-6312
Mfr. Part No.2810612
£120.14
Each
Units
5:1 - - - 24 V dc 5A 0 → 20 mA 104mm -20°C 22.5mm +65°C 114.5mm - -
RS Stock No. 337-2752
Mfr. Part No.2814744
£222.11
Each
Units
55:1 - - - 20 → 30 V dc 55A 0 → 20 mA 99mm -20°C 22.5mm +60°C 114.5mm - -
RS Stock No. 337-2718
Mfr. Part No.2814715
£200.90
Each
Units
11:1 - - - 20 → 30 V dc 11A 0 → 20 mA 99mm -20°C 22.5mm +60°C 114.5mm - -
RS Stock No. 337-2724
Mfr. Part No.2814731
£222.11
Each
Units
- - - - 20 → 30 V dc - - - - - - - - -
RS Stock No. 801-6255
Mfr. Part No.2813457
£142.44
Each
Units
100:1 18.5mm - - 20 → 30 V dc 100A - 85mm -20°C 55mm +60°C 70.5mm - -
RS Stock No. 801-6296
Mfr. Part No.2810625
£139.77
Each
Units
5:1 - - - 19.2 → 253 V ac/dc 5A 0 → 20 mA 104mm -20°C 22.5mm +65°C 114.5mm - -
RS Stock No. 175-0492
Mfr. Part No.2906236
£308.79
Each
Units
4000:1 - DIN Rail Mounted - - 4000A 0 → 10 mA, 0 → 20 mA, 0 → 21 mA, 2 → 10 mA, 4 → 20 mA 110.5mm -40 °C, -30°C 120.5mm +70 °C, +80°C 6.2mm 6.2 x 120.5 x 110.5 mm Retrofitting
New
RS Stock No. 207-4842
Mfr. Part No.1058044
£443.57
Each
Units
- - DIN Rail Mounted - - 1.5 kA, 1 kA, 2 kA, 4 kA, 100 A, 250 A, 400 A, 630 A, - 1 A 85mm - 22.5mm - - - -
RS Stock No. 175-0493
Mfr. Part No.2906234
£308.79
Each
Units
4000:1 - DIN Rail Mounted - - 4000A 0 → 10 mA, 0 → 20 mA, 0 → 21 mA, 2 → 10 mA, 4 → 20 mA 110.5mm -40 °C, -30°C 120.5mm +70 °C, +80°C 6.2mm 6.2 x 120.5 x 110.5 mm Retrofitting
RS Stock No. 174-3478
Mfr. Part No.2910326
£285.66
Each
Units
4000:1 - DIN Rail Mounted - - 4000A 1 A 70.4mm -30 °C, -20°C 22.5mm +70 °C, +80°C 85mm 22.5 x 85 x 70.4 mm Retrofitting
RS Stock No. 174-3479
Mfr. Part No.2910325
£264.83
Each
Units
4000:1 - DIN Rail Mounted - - 4000A 1 A 70.4mm -30 °C, -20°C 22.5mm +70 °C, +80°C 85mm 22.5 x 85 x 70.4 mm Retrofitting
RS Stock No. 175-0490
Mfr. Part No.2907888
£4.28
Each
Units
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