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. 331-597
Mfr. Part No.CT132M40/5-1/3
BrandHOBUT
€12.88
Each
units
40:5 21mm DIN Rail Mounted - - 40A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 331-474
Mfr. Part No.CT132M50/5-1/1
BrandHOBUT
€12.88
Each
units
50:5 21mm DIN Rail Mounted - - 50A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 775-2714
Mfr. Part No.CTSCMICRO19-200/5-T-S
BrandHOBUT
€45.76
Each
units
200:5 - Split Core - - - - 78mm -30°C 58mm +55°C 49mm - -
RS Stock No. 499-5564
Mfr. Part No.AP 50 B420L
BrandLEM
€134.67
Each
units
50:1 18mm - - 12 → 24 V dc 50A 4 → 20 mA 69mm -20°C 67mm +60°C 55mm - -
RS Stock No. 819-9779
Mfr. Part No.90AS
BrandEfergy
€11.25
Each
units
- 12mm Split Core - - - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders
RS Stock No. 914-5290
Mfr. Part No.CTSCMWH30/0.333V
BrandHOBUT
€19.85
Each
units
- 10mm Split Core - - 30A 333 mV - -15°C - +50°C - 28.7 x 26.4 x 41.7 mm Multi Function Meter
RS Stock No. 499-5586
Mfr. Part No.AP 200 B420L
BrandLEM
€134.67
Each
units
200:1 18mm - - 12 → 24 V dc 200A 4 → 20 mA 69mm -20°C 67mm +60°C 55mm - -
RS Stock No. 351-106
Mfr. Part No.MI20
€38.51
Each
units
20:1 - - - - 20A - 45mm -20°C 52mm +60°C 16mm - -
RS Stock No. 775-2701
Mfr. Part No.CTSCMICRO19-100/5-T-S
BrandHOBUT
€45.76
Each
units
- - - - - - - 78mm -30°C 58mm 55°C 49mm - -
RS Stock No. 914-5313
Mfr. Part No.CT132TRAN20A-5/10V
BrandHOBUT
€33.76
Each
units
20:1 21mm - - 15 → 30 V 20A - 65mm -15°C 45mm +50°C 30mm - -
RS Stock No. 286-311
Mfr. Part No.LA 25-NP
BrandLEM
€22.87
Each
units
36:1 - - Closed Loop 15 V 36A 25 mArms 16.45mm -40°C 26mm +85°C 29.2mm - -
RS Stock No. 914-5307
Mfr. Part No.CTSCMWH250/0.333V
BrandHOBUT
€26.37
Each
units
- 24mm Split Core - - 250A 333 mV - -15°C - +50°C - 43.5 x 38.6 x 69.6 mm Multi Function Meter
RS Stock No. 446-0620
Mfr. Part No.DK 200 B420
BrandLEM
€389.81
Each
units
200:1 21.7mm - Open Loop 20 → 50 V dc 200A 4 → 20 mA 68.6mm -20°C 89.7mm +50°C 30.2mm - -
RS Stock No. 287-3125
Mfr. Part No.CT151M25/5-2.5/3
BrandHOBUT
€16.17
Each
units
25:5 14mm Straight Through - - - - 75mm -20°C 54.5mm +70°C 68mm - -
RS Stock No. 446-0614
Mfr. Part No.DK 100 B420
BrandLEM
€398.48
Each
units
100:1 21.7mm - Open Loop 20 → 50 V dc 100A 4 → 20 mA 68.6mm -20°C 89.7mm +50°C 30.2mm - -
RS Stock No. 287-3131
Mfr. Part No.CT151M40/5-2.5/3
BrandHOBUT
€15.39
Each
units
40:5 14mm Straight Through - - - - 75mm -20°C 54.5mm +70°C 68mm - -
RS Stock No. 497-182
Mfr. Part No.HASS 50-S
BrandLEM
€17.21
Each
units
150:1 20.4 x 10.4mm - Open Loop 5 V 150A - 30mm -40°C 40mm +85°C 30mm - -
RS Stock No. 533-0621
Mfr. Part No.CTSCEN200<1000/5
BrandHOBUT
€75.65
Each
units
200:5, 400:5, 600:5, 800:5, 1000:5 - Clip Fit - - - - 125mm -30°C 132mm +80°C 38mm - -
RS Stock No. 914-5310
Mfr. Part No.CT132TRAN10A-5/10V
BrandHOBUT
€33.76
Each
units
10:1 21mm - - 15 → 30 V 10A - 65mm -15°C 45mm +50°C 30mm - -
RS Stock No. 772-1221
Mfr. Part No.5SV8702-0KK
BrandSiemens
€138.53
Each
units
- 35mm Toroidal Ring - - - - 79mm -10°C 100mm +50°C 58.8mm - -