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. 418-3604
Mfr. Part No.CTSCEN100<400/5
BrandHOBUT
MYR432.64
Each
units
100:5, 200:5, 300:5, 400:5 - Clip Fit - - - - 113mm -30°C 127mm +80°C 40mm - -
RS Stock No. 286-361
Mfr. Part No.LV 25-P
BrandLEM
MYR313.27
Each
units
14:1 - - Closed Loop 12 → 15 V 14A 25 mA 16.45mm 0°C 26mm +70°C 29.2mm - -
RS Stock No. 914-5310
Mfr. Part No.CT132TRAN10A-5/10V
BrandHOBUT
MYR156.23
Each
units
10:1 21mm - - 15 → 30 V 10A - 65mm -15°C 45mm +50°C 30mm - -
RS Stock No. 914-5288
Mfr. Part No.CT132TRAN100A-4/20MA
BrandHOBUT
MYR187.89
Each
units
100:1 21mm - - 15 → 30 V 100A 4 → 20 mA 65mm -15°C 45mm +50°C 30mm - -
RS Stock No. 537-4485
Mfr. Part No.AC-1005
MYR19.386
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. 819-9779
Mfr. Part No.90AS
BrandEfergy
MYR64.80
Each
units
- 12mm Split Core - - - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders
RS Stock No. 497-221
Mfr. Part No.LA 25-P
BrandLEM
MYR319.64
Each
units
55:1 - - Closed Loop 12 → 15 V 55A 25 mArms 27.2mm -25°C 36.5mm +85°C 14.45mm - -
RS Stock No. 914-5313
Mfr. Part No.CT132TRAN20A-5/10V
BrandHOBUT
MYR155.01
Each
units
20:1 21mm - - 15 → 30 V 20A - 65mm -15°C 45mm +50°C 30mm - -
RS Stock No. 181-2129
Mfr. Part No.CSLA2CD
BrandHoneywell
MYR104.25
Each
units
- 10.9mm - Open Loop 6 → 12 V dc - - - - - - - - -
RS Stock No. 321-6286
Mfr. Part No.LAH25-NP
BrandLEM
MYR94.19
Each
units
25:1 - - Closed Loop 12 → 15 V 25A 25 mArms 21mm -25°C 33.3mm +85°C 14.93mm - -
RS Stock No. 121-8179
Mfr. Part No.CSLA2DK
BrandHoneywell
MYR210.51
Each
units
20:1 - - - 6 → 12 V dc 20A Maximum of 400 A 44.5mm -25°C 35.6mm +85°C 14.2mm - -
RS Stock No. 499-5536
Mfr. Part No.AP 50 B10
BrandLEM
MYR521.57
Each
units
50:1 18mm - Closed Loop 24 V dc 50A - 69mm -20°C 67mm +60°C 55mm - -
RS Stock No. 321-6315
Mfr. Part No.LTS 15NP
BrandLEM
MYR76.66
Each
units
48:1 3.2mm - Closed Loop 5 V 48A - 24mm -40°C 22.2mm +85°C 10mm - -
RS Stock No. 169-7656
Mfr. Part No.CSLA2DK
BrandHoneywell
MYR182.79
Each (In a Box of 50)
units
- - - - 6 → 12 V dc - Maximum of 400 A 44.5mm -25°C 35.6mm +85°C 14.2mm - -
RS Stock No. 914-5294
Mfr. Part No.CTSCMWH60/0.333V
BrandHOBUT
MYR116.56
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
RS Stock No. 914-5301
Mfr. Part No.CTSCMWH500/0.333V
BrandHOBUT
MYR218.60
Each
units
500:1 35mm Split Core - - 500A 333 mV - -15°C - +50°C - 51.2 x 51.2 x 83.5 mm Multi Function Meter
RS Stock No. 527-8466
Mfr. Part No.DHR 100 C420
BrandLEM
MYR892.14
Each
units
100:1 32mm - Open Loop 20 → 50 V dc 100A 4 → 20 mA 70mm -40°C 90mm +70°C 25mm - -
RS Stock No. 123-6725
Mfr. Part No.XN45-315051S000000
MYR165.02
Each
units
400:5 31mm Base Mounted - - 400A 5 A - - - - - 141 x 38 x 102.5 mm MCCB
RS Stock No. 301-9495
Mfr. Part No.HAS 100S
BrandLEM
MYR118.08
Each
units
300:1 20.4 x 10.4mm - Open Loop 15 V 300A - 30mm -10°C 40mm +80°C 30mm - -
RS Stock No. 397-9117
Mfr. Part No.BZCT035
MYR195.04
Each
units
- 35mm - - - - - 74mm -20°C 64mm +60°C 40mm - Broyce Type A Earth Leakage Relays