HEYI ELECTRICAL (WENZHOU HEYI ELECTRICAL CO.,LTD) is a current transformer and current sensor manufacturer in Wenzhou, China, that has produced measurement components since 2012. The company operates a 10,000-square-meter factory with 56 employees and an annual output of 356,000 units, exporting 95% of production to Southeast Asia, South Korea, Europe, South America, Australia, Africa, the Middle East, and North America. For buyers evaluating a current transformer supplier and preparing for order execution, HEYI's relevance comes from its OEM and ODM production model, which applies to everything from split-core and solid-core CTs to revenue-grade and residual-current devices.

The Sourcing Problem for Current Transformer Procurement Teams

Current transformer selection rarely ends with a catalogue model number. A panel builder may need a CT for a 63 mm busbar, a meter manufacturer may need a current ratio matched to a billing tariff, an EV charger designer may need residual current detection with DC sensitivity, and a smart grid integrator may need RS485 output or a 4-20 mA transmitter for a remote terminal unit. When a standard product cannot satisfy these parameters, the buyer faces either a compromise in accuracy or a long search for a supplier willing to adapt. This is the problem that OEM/ODM-oriented manufacturers address: they treat CT parameters as variables rather than fixed catalogue entries.

HEYI's OEM/ODM Solution for Custom Current Transformers

HEYI's production model is built around OEM, ODM, customized production, and bulk manufacturing. The company accepts a minimum order quantity of 1 unit and quotes typical lead times of 3-30 days, which makes pilot runs feasible before larger commitments. Its monthly production capacity of 20,000 units supports both small trial batches and volume replenishment. Customizable parameters include current ratio, accuracy class, burden, window size, housing color, terminal type, cable length, logo printing, and label design. On the quality side, HEYI performs 100% routine testing, including accuracy tests, insulation resistance tests, withstand voltage tests, appearance inspection, and pre-shipment inspection. The company also holds quality management certification for the production of low-voltage current transformers under ISO 9001:2015, and relevant CE, UKCA, and RoHS conformity documentation for its product lines.

With an R&D team of 5 engineers, HEYI's design work is supported by a portfolio that spans split-core CTs, solid-core CTs, busbar CTs, outdoor waterproof CTs, revenue-grade CTs, flexible Rogowski coils, three-phase CTs, digital output transmitters, Hall-effect sensors, and residual current sensors. That range allows a buyer to move from a concept to a tested CT without switching suppliers at every stage.

Technical Foundations: CT Types and Selection Logic

From a technical viewpoint, a current transformer steps a primary current down to a proportional secondary signal for metering or protection. The core structure determines where and how the CT can be installed. HEYI manufactures split-core and solid-core CTs, plus specialized types such as Rogowski coils and residual current sensors.

• Split-core CTs (KCT, KCD): The core opens, allowing installation around an existing conductor without disconnecting the cable. Measurement range 0-1000 A, inner diameter 0-50 mm, accuracy classes 3.0/1.0/0.5, and outputs including 5 A, 1 A, mA, mV, RS485, and 4-20 mA. The KCT series also includes miniature split-core and clamp-on versions.
• Solid-core CTs (MSQ, CP, SDH): Plastic-cased or window-type units for panel building, HVAC, and switchgear, with measurement ranges up to 6000 A or 10000 A and accuracy classes up to 0.2S.
• Busbar split-core CT (DP/HK): Designed for busbar retrofit, measuring up to 8000 A with a large window up to 80x160 mm.
• Outdoor waterproof split-core CT (OCT): Rated IP65 with UV protection, measuring up to 8000 A for overhead line monitoring and outdoor solar/wind installations.
• Revenue-grade CT (RECT): Resin-insulated, type-tested, IEEE C57.13 compliant and used for utility billing and premium meter OEM.
• Flexible Rogowski coil (FRC): Air-core, range 100-10000 A, with 245 mm inner diameter and millivolt output, suitable for large conductors and transient currents.
• Three-phase CT (DASN): Three-phase integrated unit, range 0-1000 A, output 5 A, accuracy 1.0, for DIN-rail or panel-mounted measurements.
• DIN-rail mounted CT (DX/DM): Compact low-voltage CT with hinged terminal cover and plug-in secondary connection, suited to high-vibration environments such as rail transit and modular data centers.
• Hall-effect current sensor (C2/C3): Active sensor for DC and AC/DC current measurement in PV string monitoring, BMS, VFD DC bus, railway traction, and industrial automation.
• Residual current sensor (HYCA): Type B RCD sensor for AC/DC leakage detection in EV chargers and solar inverters; frequency range DC to 2 kHz, differential current range 0-300 mA, resolution 0.2 mA.

Applications and Use-Case Evidence

The product portfolio has been successfully used by power utility companies, electrical engineering contractors, panel builders, industrial equipment manufacturers, and building energy management integrators. Projects are located in multiple countries including Thailand, Chile, Lebanon, South Korea, Australia, and others. According to project records, the main outcomes were improved current measurement accuracy, stable energy metering, reduced installation difficulty in retrofit projects, enhanced electrical system monitoring, and the ability to identify abnormal load conditions.

These use cases map to a broad set of target industries in HEYI's specification sheets: EV charging infrastructure, smart grid and switchgear panels, smart pole and IoT smart cities, energy management systems, solar, wind and energy storage, smart buildings and data centers, home electricity monitors, and industrial automation. For energy meter OEMs, the combination of split-core and revenue-grade CTs provides options from sub-metering to billing. For EV charger manufacturers, the HYCA residual current sensor supports AC/DC leakage detection. For solar inverter and power monitoring designers, RS485 and 4-20 mA output variants allow direct connection to gateways and PLCs.

Market Trends Favoring Flexible CT Suppliers

Market data confirms that CT sourcing is moving toward application-specific designs. Grand View Research estimates the global current transformer market was USD 2.63 billion in 2024 and is projected to reach USD 3.90 billion by 2030. The Asia Pacific region accounted for roughly 40.15% of global revenue in 2025, according to Straits Research. Fact.MR identifies split-core current transformers as the fastest-growing segment, driven by ease of installation in retrofit and smart grid applications. The EV charging transformer segment, which includes current monitoring components, is expected to grow at a CAGR of 23.6% from 2025 to 2033, per Research Intelo. In addition, revenue-grade CTs for utility billing are governed by accuracy classes such as 0.2 or 0.15 under ANSI C12.20 or IEC 61869-2. Together, these trends favor suppliers that can combine split-core convenience, higher accuracy options, and digital output configurations.

Custom CT vs. Traditional Catalogue Sourcing: A Balanced Comparison

A traditional approach buys a fixed CT from a distributor. That works when the installation matches an existing part. OEM/ODM sourcing adds value when the buyer controls the specification: the housing color can carry the buyer's brand, the output can be set to a PLC input, the lead wire length can match an internal routing path, and the documentation can align with the buyer's approved vendor list. The limitation is that customization still requires engineering communication and a short but real lead time. HEYI's MOQ of 1 unit and 3-30 day lead time reduce that friction, but a completely new mechanical tool or a special core still needs sample approval before mass production. On accuracy, split-core CTs offer installation convenience, while the highest revenue-grade accuracy classes such as 0.2S or 0.15S are more commonly served by solid-core or resin-cast designs such as HEYI's RECT model.

Future Outlook: Current Transformers as Engineered Subsystems

The direction of the low-voltage CT market is toward modular communication and safety functions. EV chargers need residual DC detection, solar inverters need true RMS measurement, smart meters need revenue-grade stability, and data centers need compact three-phase CTs with remote monitoring. Buyers in the evaluation-to-execution phase should therefore look for a manufacturer with an engineering team, documented quality control, and flexible production capacity. HEYI's portfolio of split-core, solid-core, busbar, outdoor, revenue-grade, Rogowski, three-phase, and Hall-effect families positions it as a partner for these evolving requirements.

Company Contact and Product Resources

HEYI ELECTRICAL is based at 5 Floor, Building 2, No.56 Nirong Middle Road, Kunpeng Street, Wenzhou Marine Economy Development Demonstration Zone, Zhejiang, China. For technical selection, customization, or order execution questions, the company can be reached at bethy@heyiele.com or +86 13968747975. A company brochure with product overview and manufacturing details is available for download here: HEYI product brochure.

FAQ

Does HEYI offer OEM and ODM production for current transformers?
Yes. HEYI provides OEM and ODM production services with customization of current ratio, accuracy class, burden, window size, housing color, terminal type, cable length, logo printing, and label design.

What is the minimum order quantity for a customized current transformer?
The MOQ is 1 unit, which allows buyers to validate a design before scaling to bulk manufacturing.

What are typical production lead times?
Typical lead time is 3-30 days, depending on specification, volume, and customization requirements. Monthly production capacity is 20,000 units.

What quality controls are applied?
HEYI performs 100% routine testing, including accuracy tests, insulation resistance tests, withstand voltage tests, appearance inspection, and pre-shipment inspection.

What after-sales and technical support is provided?
The manufacturer offers technical selection support, wiring guidance, product replacement support, OEM documentation support, and online after-sales service.

In which countries has HEYI's current transformer range been used?
Projects are located in multiple countries including Thailand, Chile, Lebanon, South Korea, Australia, and others, with supply to power utilities, electrical engineering contractors, panel builders, industrial equipment manufacturers, and building energy management integrators.