current transformer - precise measurement, diverse approaches
Our current transformers enable the precise, safe measurement and monitoring of currents in low-voltage systems – from the plug-on to the split-core version, for measuring and protection purposes.
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Low-voltage current transformers for precise measurement and protection
Our current transformers cover primary rated currents from 1 bis 8000 A and secondary rated currents from 1 or 5 A. They are suitable for a wide range of applications in power distribution, for measurement and protection purposes. Thanks to precise manufacturing and high accuracy classes, they are ideal for industrial applications and energy suppliers.
Technical features at a glance
- Measurement of mains currents in the low-voltage range
- Primary rated current: 1 bis 8000 A
- Secondary rated current: 1 A or 5 A
- Accuracy classes: 0.2s, 0.2, 0.5s, 0.5, 1, 3
- Versions for measurement or protection available
- Touch protection included in scope of delivery (secondary side)
- Mounting on 35 mm DIN rail (DIN 50022) possible
- Optional: current transformers approved for billing purposes
- Wide range of accessories available
Safety notice
When operating with an open secondary circuit, dangerous voltages can occur. Especially with protection current transformers, voltages of several kilovolts are possible. Operation with an open secondary circuit is therefore strictly prohibited.
Definitions and important terms
- Rated transformation ratio: Ratio of primary to secondary rated current (e.g. 200/5)
- Standardised primary rated currents: 5 A bis 5000 A (decadically graduated)
- Secondary rated currents: 1 A or 5 A
- Rated frequency: Standard: 50–60 Hz (other frequencies on request)
- Rated voltage: Insulation rating according to standard (e.g. 1 kV)
- Rated burden and power: Relevant for error limits (1–45 VA)
- Accuracy classes: 0.1 bis 3 – from precision to coarse measurement
- Thermal rated load capacity: Ith = 60 × In
Versions and standards
Our current transformers are manufactured according to the following standards: IEC 185, VDE 0414, DIN 42600. The housing is made of impact-resistant, flame-retardant plastic (Makrolon, black). Secondary terminals are nickel-plated and equipped with combination screws. Ultrasonic-welded design for maximum safety.
Application
Current transformers transform mains currents to standardised secondary values for safe and accurate measurement. They also provide protection against overcurrents and galvanically isolate the measuring circuit from the mains.
Special advantages of our current transformers
- Robust and durable design
- High measurement accuracy
- Large connection terminals for easy installation
- Touch protection according to VBG 4
- Transformer mounting included
- Many models and designs available
- Billing-capable transformers on request
Standards and recommendations
- IEC 185 (1975)
- VDE 0414, parts 1–3
- DIN 42600
- VDE 1000
- Insulation class: E
Special versions
Individual solutions are available on request. If you cannot find a specific model, please contact us. Special current transformers approved for billing purposes are also available.
Frequently asked questions
It mainly depends on three factors: the primary current to be measured, the existing conductor shape (busbar, round conductor or existing cable) and the intended use (measurement or protection). For a quick preselection, describe your system to us via our contact form or call us – we will recommend the suitable type to you.
The design depends on the existing conductor shape: plug-on current transformers (ASK) are suitable for copper busbars and round conductors, wound-type current transformers (WSK) for conductors routed through the transformer window, and split-core current transformers (KBR/KBU) for subsequent installation around an existing cable. In addition, the transformation ratio, burden (rated power) and accuracy class must match the application.
The accuracy class (e.g. 0.2s, 0.5 or 1) indicates the maximum permissible deviation of the measured secondary quantity from the actual value under rated conditions. Lower values mean higher precision. For billing measurements, finer classes are generally specified than for pure monitoring or protection applications.
Yes, current transformers are frequently used for self-consumption measurement and monitoring in PV systems, for example in conjunction with energy meters or monitoring systems. Which transformer is suitable for the respective inverter and meter system depends on the primary current and the connection requirements – please contact us if you have any questions.
Measuring current transformers are designed for precise measurement in the rated current range and deliberately enter saturation at very high currents in order to protect connected measuring instruments from overload. Protection current transformers, on the other hand, are designed to operate as linearly as possible even at high short-circuit currents, so that connected protection relays trip correctly and in good time.
current transformer correctly mount
- Before mounting, ensure that the system is de-energized, provided that the mounting instructions of the respective product require this.
- Select the transformer suitable for the conductor shape (busbar, round conductor or cable) and the required transformation ratio.
- Mount the current transformer according to the intended fastening (foot or rail mounting) and ensure a secure fit.
- Connect the secondary circuit to a suitable measuring device or protection relay – the secondary circuit must never remain open during operation.
- Before disconnecting measuring devices in the secondary circuit, always first set a short-circuit bridge to avoid operating the secondary circuit open.
- Attach the insulating protective cap and secondary sealing caps, if available, for touch-safe operation.