Discrete Current Transformers in Power Measurement Systems

1. Why is it difficult to measure current in existing electrical systems?

Installing electricity meters on an existing electrical network is no easy task. Distribution boxes may already be connected to cables, space may be limited, and disconnecting lines increases installation time.

Removable current transformers offer a practical solution, as they can be removed without interrupting the electrical circuit and installed alongside existing wiring. This feature makes this design particularly suitable for modernizing energy measurement and monitoring systems.

The HEYI KCT series incorporates a clip-on fixing system that allows installation even in confined spaces and use near cables without the need to disconnect existing circuits.

2. In what areas can discrete current transformers be used in measurement systems?

2.1 Current measurement system

The current transformer used in electricity meters converts the primary current into a lower amplitude signal that the meter can measure.

Based on the KCT model, HEYI offers various output signal options, including milliamp signals and a 0.333 V output voltage. This series is designed for current, power, and energy monitoring applications.

This makes the KCT product range ideal for device manufacturers developing external energy meters, energy monitoring devices, and measurement systems associated with current transformers.

2.2 Submeter Installation Project

If users want to measure the energy consumption of each line, customer, device, or electrical load, they typically need current transformers to perform customer-level measurement.

This modular design is very useful in this type of project, as it allows measurement functions to be integrated into an existing system without the need to completely rewire the system.

Typical application areas include:

• commercial building
• Factory
• Distribution box
• Equipment for heating, ventilation and air conditioning (HVAC) systems.
• Engine
• Lighting circuit
• Automated systems

KCT’s product catalog lists compatible measurement applications, including motors, lighting, compressors, HVAC systems, and automation systems.

3. Why is an output voltage of 333 mV important for modern measuring instruments?

3.1 Low voltage signal at the device interface

In electronic measuring instruments, the type of output signal of the current transformer is an important selection parameter.

The 333mV plug-in current transformer provides a low-voltage secondary signal and can be connected to compatible energy monitoring devices.

Currently, HEYI offers 0.333 V options for different KCT sizes. For example, the KCT-16 supports a current of 100 to 200 A at 0.333 V, while the KCT-24 supports a current of 100 to 400 A at 0.333 V.

The KCT-36 is also available in a 300-600 A/0.333 V version, allowing meter manufacturers to use the same discrete core concept to meet the requirements of higher power applications.

3.2 Different output parameters according to different device designs

Not all electricity meters use the same current transformer input.

Therefore, the following factors should be considered when choosing a current sensor:

• Nominal current
• Secondary exit
• Meter input signal requirements
• Cable size
• Computed tomography window size
• installation location

The KCT series includes versions with secondary output for low currents and voltage output, giving device developers more options when adapting current transformers to measurement platforms.

4. How do electricity meter manufacturers select the appropriate KCT model?

4.1 Selection based on current scope

The KCT series includes a wide variety of main current sizes and ranges.

For low-power applications, the KCT-6 and KCT-10 models offer a compact solution. For higher loads, the range includes the KCT-16, KCT-24, and KCT-36 models.

The KCT-50 model further expands the range of configurations to 600 A, 800 A and 1000 A.

This allows meter manufacturers to use current transformers of different sizes for branch circuits, feed lines and high current monitoring, while maintaining a similar product concept.

4.2 Take into account the installation space and the cable cross-section.

Electrical cabinets are rarely exactly identical.

Some applications require the installation of small current transformers around a single conductor, while others require larger openings to accommodate thicker cables.

The KCT series is available in various frame and window sizes. The catalog also includes large interior windows of different dimensions, compatible with a wide range of existing systems.

Therefore, when developing measuring instruments for device manufacturers, the choice of current transformers should be based on electrical parameters and mechanical installation requirements.

5. Is the KCT series suitable for your energy measurement or monitoring project?

The performance of a discrete current transformer depends not only on its turns ratio. The installation method, output signal, current range, and mechanical dimensions also influence its ability to be successfully integrated into the overall system.

The HEYI KCT series offers a variety of discrete core sizes, current ranges, and output voltage options suitable for energy measurement and monitoring applications.

If you develop electricity meters, energy consumption measurement devices, or energy monitoring systems, you can send us your information:

Instrument input signal + current measurement range + cable diameter + required accuracy + annual consumption

We can help you choose the most suitable KCT configuration.

Compay：HEYI Electrical Co., Ltd.
Brand: HEYI/ASCT
Contact: Bethy
E-mail: heyi@heyiele.com             
Tel: 86-13968747975

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