Struggling to pass IEC/VDE residual current certifications for new inverters, dragging product launch timelines on and on?

Frequent unplanned shutdowns caused by false residual current detection in power stations lead to severe power generation losses and constant customer complaints?

Mass buzzing issues break out in batches with open-loop solutions, resulting in high rework costs and damaged brand reputation?

Wondering how to resolve the four major pain points of PV inverters?

Solve Four Major Pain Points of PV Inverters: Compliance Barriers, Buzzing Noise, False Trips & High Costs

Amid the deep advancement of the dual carbon strategy, the PV industry is experiencing explosive growth. As the core safety protection barrier for PV inverters, residual current detection is not only a mandatory compliance red line under international standards but also a long-standing industry challenge. High-performance closed-loop solutions come with steep costs, while low-cost open-loop solutions deliver compromised performance—an impasse that has long prevented manufacturers from balancing compliance, reliability and cost reduction.

As a leading domestic supplier of electricity sensing and control solutions, Magtron has newly launched the low-cost closed-loop fluxgate residual current sensors MRSB01S/NP and MRSB01S/2P06. Custom-engineered for RCMU/GFCI applications in PV inverters, these products leverage self-developed core technologies to break industry bottlenecks, delivering top-tier closed-loop performance at affordable open-loop pricing and fully addressing all residual current detection pain points across PV inverter scenarios.

Key Highlights of This Article

· A full breakdown of international compliance red lines and core operating condition challenges for PV inverter residual current detection

· Complete comparison of advantages and disadvantages of 3 mainstream detection solutions to help you avoid selection pitfalls

· In-depth analysis of Magtron’ core technological breakthroughs for the MRSB series, enabling dual improvements in performance and cost

· Full-scenario selection guide and sample application channel

I. Residual Current Detection: Non-Negotiable Compliance Red Line & Operational Necessity

The reliability of residual current detection directly determines market access eligibility, operational safety and full-lifecycle revenue of PV inverters, making it both a baseline compliance requirement and a core product competitive advantage.

(1) Mandatory Compliance Under International Standards — Non-Compliance Equals Barred Market Access

Stringent, explicit mandatory regulations governing residual current protection for PV inverters have been enforced across major global markets, serving as the first threshold for product commercialization.

· European standard VDE 0100-530 clearly stipulates: If electrical equipment on the load side is capable of generating pure DC residual currents, a Type B residual current device (RCD) must be installed, capable of detecting all residual current types including power-frequency AC, pulsating DC, smooth DC and non-power-frequency AC. Improper product selection will directly block market entry into core overseas markets such as the EU, and may even trigger product recalls and liability risks for compliance violations.

VDE 0100-530: General conditions for the selection and installation of residual current devices (RCDs) “If components of electrical equipment that are being installed as fixtures at the load side of a residual current device (RCD) could generate pure DC residual currents, then the residual current protective device (RCD) must be of Type B”

· International standard IEC 62109-2 specifies two core mandatory test requirements for PV inverters:

1. Continuous residual current test: The inverter must reliably trip upon sustained residual current. The test current shall rise to 300mA within 30 seconds, with five measured trip values all ≤300mA (for inverters ≤30kW).

2. Sudden residual current test: On the basis of capacitive residual current, the inverter shall cut off power protection within the specified time for abrupt resistive residual currents of 30mA/60mA/150mA, with compliance required for both positive and negative polarities. Products failing these tests cannot complete certification and enter the market.

(2) Extreme Challenges of Real-World Operating Conditions Impose Strict Requirements on Sensor Performance

With the wide adoption of high-speed switching devices such as SiC MOSFETs in PV inverters, system switching frequencies keep rising, creating far more complex field operating conditions than laboratory environments and imposing multiple stringent demands on sensor performance.

1. PV systems generate complex mixed residual currents including power-frequency AC, DC and high-frequency harmonic components, which cannot be fully and accurately detected by conventional sensors.

2. Capacitive residual current follows the core formula I = C × dU/dt, where residual current magnitude is proportional to system parasitic capacitance and voltage slew rate. Both parameters are growing exponentially:

o SiC devices deliver ultra-fast voltage transients: Traditional IGBTs achieve a dU/dt of only 2–5kV/μs, while SiC devices reach 10–20kV/μs, generating massive high-frequency harmonic components above 10kHz.

o Parasitic capacitance rises significantly in commercial & industrial energy storage systems: Superimposed parasitic capacitance from battery packs, PCS converters and long-distance cables, combined with circuit conduction in transformerless topologies, creates steady-state capacitive residual currents exceeding 1A, posing severe challenges to conventional solutions.

Sharply increased system voltage slew rates exacerbate high-frequency capacitive residual current issues. Sensors with insufficient bandwidth, slow response or high zero drift are prone to false shutdowns, missed trips or failure to trigger protection. Consequences range from frequent inverter outages causing revenue loss to catastrophic safety hazards including electric shock and equipment burnout, resulting in costly claims and ruined brand reputation.

Given these strict compliance mandates and complex operating condition challenges, can the industry’s mainstream detection solutions deliver fully satisfactory performance? We analyze each option in detail below.

II. Plight of Mainstream Industry Solutions: The Unbridgeable Gap Between High Performance & Low Cost

Three mainstream fluxgate technology solutions are currently used for PV inverter residual current detection, all trapped by the industry-wide bottleneck of “high performance = high cost”, unable to simultaneously satisfy compliance, reliability and cost-reduction targets.

1. Open-Loop Fluxgate Solution

The dominant low-cost solution for small-power inverters, open-loop fluxgates detect residual current signals via magnetic core saturation, a mature, widely adopted technology with strong cost competitiveness.

· Core Advantages: Cost-effective, capable of DC residual current detection, meets basic Type B compliance requirements, suitable for mass production and cost reduction.

· Core Drawbacks: Limited signal bandwidth due to working principles, weak detection performance under high-frequency capacitive residual current scenarios; excitation frequencies fall within the human audible range, leading to widespread buzzing noise risks if production and structural control are inadequate.

2. Traditional Closed-Loop Fluxgate Solution

The standard configuration for medium-to-high power and premium inverters, traditional closed-loop fluxgates operate on the zero-flux principle, offsetting measured magnetic fields via feedback windings to maintain the magnetic core within its optimal linear operating range, delivering superior performance.

· Core Advantages: High precision, low zero drift, wide bandwidth, fast response, stable performance across full temperature ranges, fully compatible with Type B detection for all residual current types, effortlessly meets all IEC, VDE and other international standards, strong anti-interference and reliable operation.

· Core Drawbacks: Prohibitive overall costs limiting widespread adoption; reliance on imported core ICs with uncontrollable lead times; expensive permalloy magnetic cores driving up material costs; traditional packaging structures further increase assembly costs, making them incompatible with cost-reduction targets for budget inverters.

Comparative Summary of Mainstream Technical Solutions

In summary, mainstream industry solutions cannot resolve the core trade-off between high performance and low cost: open-loop options hit cost targets but compromise performance, while traditional closed-loop products deliver premium performance at unaffordable price points, creating major concerns for most manufacturers.

Magtron’s newly launched MRSB series low-cost closed-loop fluxgate residual current sensors are engineered to resolve this core industry pain point.

III. Magtron’ Game-Changer: MRSB Series Low-Cost Closed-Loop Fluxgate Residual Current Sensors

Custom-designed for RCMU/GFCI residual current detection in PV inverters, the MRSB01S/NP and MRSB01S/2P06 series operate on the classic closed-loop fluxgate zero-flux principle. Three core technological innovations—self-developed ICs, optimized magnetic core structures and ultra-streamlined packaging—enable top-tier closed-loop performance at open-loop price levels, fully covering residual current detection needs for residential, commercial & industrial, and string PV inverters across all application scenarios.

1. Innovative Magnetic Core Structure & Material Optimization: Remedying Performance Shortcomings & Eliminating Industry Pain Points

As the core sensing unit of fluxgate sensors, magnetic cores directly determine detection precision, bandwidth, response speed and long-term reliability, and represent a primary driver of high costs for traditional closed-loop solutions.

· Industry Pain Point: Conventional closed-loop products adopt costly permalloy magnetic cores that inflate material expenses; open-loop solutions use iron-based cores with subpar performance, and improper process control creates widespread magnetic ring buzzing noise.

· Magtron’ Solution: The MRSB series abandons traditional material and structural constraints, replacing expensive permalloy cores in conventional closed-loop products with new low-loss magnetic materials to drastically cut raw material costs at the source. Deep magnetic circuit topology optimization delivers superior excitation characteristics, stable magnetic permeability and enhanced anti-interference performance compared to permalloy alternatives.

· Key Performance Breakthroughs:

o Full measurement range up to 1700mA, fully covering all residual current detection ranges required for PV inverters.

o 10kHz bandwidth, perfectly suited for detecting high-frequency capacitive residual currents generated by SiC devices, enabling precise capture of full-spectrum residual current signals.

o Typical full-temperature precision of 1%, zero drift as low as 8mV, no accumulated temperature drift during long-term operation with sustained consistent detection accuracy.

o Ultra-fast response time down to 20μS, rapidly capturing abrupt residual current signals to satisfy ultra-fast power cut protection requirements under IEC standards, completely eliminating missed or failed protection trips.

o Excitation frequency raised to 300–400kHz, well above the human audible range of 20Hz–20kHz, fundamentally resolving the ubiquitous buzzing noise issue plaguing open-loop solutions and greatly improving equipment operating experience and long-term reliability.

2. Self-Developed SoC ICs: Breaking Import Monopolies for Fully Self-Sufficient Supply Chains

ICs act as the “core brain” of closed-loop fluxgate sensors, defining upper performance limits, cost baselines and supply chain stability.

· Industry Pain Point: Traditional closed-loop fluxgate solutions are heavily reliant on imported ICs, incurring high procurement costs and unpredictable lead times that create critical chip shortage risks disrupting inverter manufacturers’ mass production and delivery schedules.

· Magtron’ Solution: The MRSB series integrates fully self-developed proprietary ICs with performance matching benchmark imported alternatives, integrating full functions including excitation drive, synchronous detection, signal amplification and closed-loop feedback to deliver complete control of standard closed-loop fluxgate circuits.

· Core Value Delivered to Customers:

o Full independence from imported ICs, 100% self-sufficient supply chains ensuring stable mass production delivery.

o Sharply reduced core component costs, creating ample room for overall bill-of-materials (BOM) cost reduction.

o Retains standard closed-loop peripheral circuit architecture requiring no PCB redesign, enabling rapid mass production integration and shortened new product launch cycles.

3. Extreme Structural Optimization: End-to-End Cost Reduction for Large-Scale Industry Mass Production

While maintaining electrical performance, insulation withstand voltage and long-term reliability, the MRSB series features ultra-streamlined product structure design to cut end-to-end costs and boost application flexibility for customers.

Core Parameter Comparison of MRSB Series vs. Conventional Solutions

Four Core Value Propositions of MRSB Series for Inverter Manufacturers

1. Worry-Free Compliance: Full-temperature high precision, wide bandwidth and fast response fully support Type B detection for all residual current types, enabling effortless passing of global mainstream standards including IEC62109-2 and VDE 0100-530, drastically shortening new product certification cycles and accelerating market launch.

2. Extreme Cost Reduction: Delivers top-tier closed-loop performance at open-loop pricing, slashing overall equipment BOM costs; standardized circuit design enables rapid mass production integration, cutting R&D investment and lead times.

3. Reliable Operation & Zero Customer Complaints: Fundamentally eliminates buzzing noise, stable full-temperature performance with no accumulated zero drift over long-term operation, eradicating false trips and missed protection events to drastically reduce customer complaints and rework costs while strengthening brand reputation.

4. Secure Supply Chains: Full in-house R&D and production of core ICs and magnetic cores eliminate import dependencies, guaranteeing stable, controllable lead times and completely mitigating chip shortage risks to support large-scale mass production delivery.

Conclusion

As the PV industry shifts fully from subsidy-driven growth to parity-driven development, every incremental cost optimization and reliability improvement directly shapes product market competitiveness.

A leading domestic enterprise with over a decade of deep expertise in fluxgate sensing technology, Magtron possesses full end-to-end independent capabilities spanning IC design, magnetic core R&D, sensor mass production and customized solution development. With cumulative sensor shipments exceeding ten million units and a global customer base of dozens of top new energy manufacturers, we are one of the few domestic enterprises with fully self-sufficient closed-loop fluxgate sensing technology.

The newly launched MRSB series residual current sensors leverage closed-loop fluxgate technical expertise, integrated innovations via self-developed ICs and optimized magnetic core structures to permanently break the industry bottleneck of “high performance comes with high cost”. We deliver a localized alternative for inverter manufacturers that balances performance, cost, reliability and supply chain security.

Amid the rising penetration of SiC devices, selecting a residual current sensor capable of precise high-frequency detection, accurate DC measurement, robust environmental tolerance and strict cost control will be the decisive competitive edge in the next round of product competition.