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. 819-9779
Mfr. Part No.90AS
BrandEfergy
$23.14
Each
units
- 12mm Split Core - - - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders
RS Stock No. 301-9473
Mfr. Part No.LTS 25NP
BrandLEM
$29.38
Each
units
80:1 3.2mm - Closed Loop 5 V 80A - 24mm -40°C 22.2mm +85°C 10mm - -
RS Stock No. 819-9798
Mfr. Part No.140AS
BrandEfergy
$26.03
Each
units
- 19mm - - - - - - - - - - - Oscilloscopes
RS Stock No. 497-209
Mfr. Part No.AT 50 B420L
BrandLEM
$200.07
Each
units
50:1 16mm - - 20 → 30 V dc 50A 4 → 20 mA 67mm -20°C 44.5mm +60°C 36.5mm - -
RS Stock No. 399-7339
Mfr. Part No.AS-104
$5.97
Each
units
15:1 - - - - 15A - - -40°C - +120°C - 17.2 x 20.4 x 9.53 mm -
RS Stock No. 775-2701
Mfr. Part No.CTSCMICRO19-100/5-T-S
BrandHOBUT
$101.01
Each
units
- - - - - - - 78mm -30°C 58mm 55°C 49mm - -
RS Stock No. 173-0066
Mfr. Part No.AZ-0500
$8.296
Each (In a Box of 84)
units
25:1 - - - - 25A - - -40°C - +85°C - 19.0 x 11.5 x 21.5 mm -
RS Stock No. 775-4909
Mfr. Part No.AZ-0500
$10.61
Each
units
500:1 - - - - 25A - - -40°C - +85°C - 19.0 x 11.5 x 21.5 mm -
RS Stock No. 820-0431
Mfr. Part No.2904921
$558.77
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. 532-9205
Mfr. Part No.HTFS 200-P
BrandLEM
$44.14
Each
units
300:1 22mm - Open Loop 5 V 300A - 46mm -40°C 40mm +105°C 17mm - -
RS Stock No. 533-0621
Mfr. Part No.CTSCEN200<1000/5
BrandHOBUT
$141.35
Each
units
200:5, 400:5, 600:5, 800:5, 1000:5 - Clip Fit - - - - 125mm -30°C 132mm +80°C 38mm - -
RS Stock No. 399-7244
Mfr. Part No.ASM-010
$7.93
Each
units
10:1 - - - - 10A - - -40°C - +120°C - 20.4 x 17.2 x 9.53 mm -
RS Stock No. 537-4485
Mfr. Part No.AC-1005
$6.194
Each (In a Pack of 5)
units
5:1 - - - - 5A - - -40°C - +120°C - 23.8 x 23.8 x 11.12 mm -
RS Stock No. 302-6077
Mfr. Part No.2814359
$292.50
Each
units
5:1 - - - - 5A 0 → 20 mA 99mm -25°C 22.5mm +60°C 114.5mm - -
RS Stock No. 668-4067
Mfr. Part No.CT105F250/5-2.5/1
BrandHOBUT
$76.51
Each
units
250:5 21mm Base Mounted - - - - 79mm -30°C 105mm +80°C 53mm - -
RS Stock No. 331-339
Mfr. Part No.CT132M100/5-2.5/1
BrandHOBUT
$35.79
Each
units
100:5 21mm DIN Rail Mounted - - 100A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 914-5290
Mfr. Part No.CTSCMWH30/0.333V
BrandHOBUT
$37.95
Each
units
30:1 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. 537-4520
Mfr. Part No.AC-1020
$6.194
Each (In a Pack of 5)
units
20:1 - - - - 20A - - -40°C - +120°C - 23.8 x 23.8 x 11.12 mm -
RS Stock No. 397-9123
Mfr. Part No.BZCT070
$134.45
Each
units
- 70mm - - - - - 117mm -20°C 105mm +60°C 40mm - Broyce Type A Earth Leakage Relays
RS Stock No. 331-597
Mfr. Part No.CT132M40/5-1/3
BrandHOBUT
$24.63
Each
units
40:5 21mm DIN Rail Mounted - - 40A 5 A 65mm -30°C 45mm +85°C 30mm - -