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. 919-4700
Mfr. Part No.LF 510-S
BrandLEM
HK$623.57
Each
units
800:1 - - Closed Loop ±14.25 → ±25.2 V 800A ±0.16 A 70mm -40°C 89mm +85°C 40.6mm - -
RS Stock No. 331-339
Mfr. Part No.CT132M100/5-2.5/1
BrandHOBUT
HK$138.47
Each
units
100:5 21mm DIN Rail Mounted - - 100A 5 A 65mm -30°C 45mm +85°C 30mm - -
RS Stock No. 668-4067
Mfr. Part No.CT105F250/5-2.5/1
BrandHOBUT
HK$409.12
Each
units
250:5 21mm Base Mounted - - - - 79mm -30°C 105mm +80°C 53mm - -
RS Stock No. 913-9734
Mfr. Part No.METSECT5CC013
HK$611.64
Each
units
125:5 21mm Toroidal Ring - - - - - -25°C - +60°C - 65 x 44 x 30 mm -
RS Stock No. 286-361
Mfr. Part No.LV 25-P
BrandLEM
HK$656.34
Each
units
14:1 - - Closed Loop 12 → 15 V 14A 25 mA 16.45mm 0°C 26mm +70°C 29.2mm - -
RS Stock No. 537-4485
Mfr. Part No.AC-1005
HK$32.856
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. 499-5378
Mfr. Part No.LTSR 25-NP
BrandLEM
HK$179.42
Each
units
80:1 3.2mm - Closed Loop 5 V 80A - 24mm -40°C 22.2mm +85°C 10mm - -
RS Stock No. 533-0621
Mfr. Part No.CTSCEN200<1000/5
BrandHOBUT
HK$770.98
Each
units
200:5, 400:5, 600:5, 800:5, 1000:5 - Clip Fit - - - - 125mm -30°C 132mm +80°C 38mm - -
RS Stock No. 775-4934
Mfr. Part No.ACX-1050
HK$44.41
Each
units
50:1 - - - - 50A - - -40°C - +85°C - 23.8 x 23.8 x 11.12 mm -
RS Stock No. 173-0064
Mfr. Part No.ACX-1050
HK$38.62
Each (In a Box of 240)
units
50:1 - - - - 50A - - -40°C - +85°C - 23.8 x 23.8 x 11.12 mm -
RS Stock No. 819-9779
Mfr. Part No.90AS
BrandEfergy
HK$111.94
Each
units
- 12mm Split Core - - - - - - - - - - Data Loggers/DAS, Digital or Analog Meters, DMMs, Recorders
RS Stock No. 793-4613
Mfr. Part No.DVL 1000
BrandLEM
HK$1,939.64
Each
units
- - - - ±15 → 24 V - 50 mA 48.3mm -40°C 63mm +85°C 100mm - -
RS Stock No. 446-0614
Mfr. Part No.DK 100 B420
BrandLEM
HK$4,333.57
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. 435-8735
Mfr. Part No.HX 20-P/SP2
BrandLEM
HK$105.76
Each
units
60:1 1.6mm - Open Loop 12 → 15 V 60A - 20.5mm -25°C 19mm +85°C 15.4mm - -
RS Stock No. 532-9211
Mfr. Part No.HTFS 200-P/SP2
BrandLEM
HK$222.64
Each
units
300:1 22mm - Open Loop 5 V 300A - 46.3mm -40°C 40mm +105°C 17mm - -
RS Stock No. 331-519
Mfr. Part No.CT143M100/5-2.5/1-001
BrandHOBUT
HK$146.35
Each
units
100:5 24mm DIN Rail Mounted - - 100A 5 A 70mm -30°C 49mm +85°C 45mm - -
RS Stock No. 451-1368
Mfr. Part No.LF 305S
BrandLEM
HK$575.31
Each
units
300:1 20.1mm - Closed Loop 12 → 20 V 300A 150 mArms 56.5mm -40°C 60mm +85°C 26.6mm - -
RS Stock No. 180-7357
Mfr. Part No.LA 55-P
BrandLEM
HK$239.96
Each
units
70:1 - - Closed Loop 12 → 15 V 70A 50 mArms 27.6mm -40°C 36.6mm +85°C 14.45mm - -
RS Stock No. 302-6077
Mfr. Part No.2814359
HK$2,530.94
Each
units
5:1 - - - - 5A 0 → 20 mA 99mm -25°C 22.5mm +60°C 114.5mm - -
RS Stock No. 668-4055
Mfr. Part No.CT105F150/5-2.5/1
BrandHOBUT
HK$377.62
Each
units
150:5 21mm Base Mounted - - - - 79mm -30°C 105mm +80°C 53mm - -