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. 522-030
Mfr. Part No.AT 5 B420L
BrandLEM
SGD118.99
Each
units
5:1 16mm - - 20 → 30 V dc 5A 4 → 20 mA 67mm -20°C 44.5mm +60°C 36.5mm - -
RS Stock No. 886-2109
Mfr. Part No.XW01-065081S000000
SGD29.67
Each
units
10:5 - Base Mounted - - - - - - - - - 62 x 40 x 78 mm -
RS Stock No. 331-468
Mfr. Part No.CT132M120/5-2.5/1
BrandHOBUT
SGD23.78
Each
units
120:5 21mm DIN Rail Mounted - - 120A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 286-361
Mfr. Part No.LV 25-P
BrandLEM
SGD110.09
Each
units
14:1 - - Closed Loop 12 → 15 V 14A 25 mA 16.45mm 0°C 26mm +70°C 29.2mm - -
RS Stock No. 331-430
Mfr. Part No.CT132M150/5-2.5/1
BrandHOBUT
SGD24.57
Each
units
150:5 21mm DIN Rail Mounted - - 150A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 533-0643
Mfr. Part No.CTSCM40-200/5
BrandHOBUT
SGD85.85
Each
units
200:5 - Clip Fit - - - - 104.5mm -30°C 116mm +80°C 35.5mm - -
RS Stock No. 913-9731
Mfr. Part No.METSECT5CC005
SGD79.32
Each
units
50:5 21mm Toroidal Ring - - - - - -25°C - +60°C - 65 x 44 x 30 mm -
RS Stock No. 521-992
Mfr. Part No.LF 205-S/SP3
BrandLEM
SGD105.37
Each
units
200:1 15.5mm - Closed Loop 12 → 15 V 200A 100 mArms 51.63mm -40°C 61mm +85°C 26.19mm - -
RS Stock No. 198-807
Mfr. Part No.AT 10 B10
BrandLEM
SGD82.18
Each
units
10:1 16mm - - - 10A - 67mm -20°C 44.5mm +60°C 36.5mm - -
RS Stock No. 397-9117
Mfr. Part No.BZCT035
SGD58.26
Each
units
- 35mm - - - - - 74mm -20°C 64mm +60°C 40mm - Broyce Type A Earth Leakage Relays
RS Stock No. 189-5477
Mfr. Part No.CSNE151
BrandHoneywell
SGD55.19
Each
units
36:1 - - Closed Loop 15 V 36A 25 mA 28mm 0°C 28mm +70°C 16.8mm - -
RS Stock No. 399-7244
Mfr. Part No.ASM-010
SGD7.37
Each
units
10:1 - - - - 10A - - -40°C - +120°C - 20.4 x 17.2 x 9.53 mm -
RS Stock No. 819-9779
Mfr. Part No.90AS
BrandEfergy
SGD19.35
Each
units
- 12mm Split Core - - - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders
RS Stock No. 106-8534
Mfr. Part No.56050C
SGD2.457
Each (In a Tube of 25)
units
10:1 - - - - 10A - - -40°C - +85°C - 16.79 x 8.89 x 20.19 mm -
RS Stock No. 715-7068
Mfr. Part No.56050C
SGD2.52
Each
units
10:1 - - - - 10A - - -40°C - +85°C - 16.79 x 8.89 x 20.19 mm -
RS Stock No. 331-474
Mfr. Part No.CT132M50/5-1/1
BrandHOBUT
SGD21.93
Each
units
50:5 21mm DIN Rail Mounted - - 50A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 331-597
Mfr. Part No.CT132M40/5-1/3
BrandHOBUT
SGD21.93
Each
units
40:5 21mm DIN Rail Mounted - - 40A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 286-311
Mfr. Part No.LA 25-NP
BrandLEM
SGD52.10
Each
units
36:1 - - Closed Loop 15 V 36A 25 mArms 16.45mm -40°C 26mm +85°C 29.2mm - -
RS Stock No. 497-378
Mfr. Part No.AT 50 B10
BrandLEM
SGD131.43
Each
units
50:1 16mm - - - 50A - 67mm -20°C 44.5mm +60°C 36.5mm - -
RS Stock No. 914-5294
Mfr. Part No.CTSCMWH60/0.333V
BrandHOBUT
SGD33.80
Each
units
60:1 10mm Split Core - - 60A 333 mV - -15°C - +50°C - 28.7 x 26.4 x 41.7 mm Multi Function Meter