Solar energy systems are playing an increasingly critical role in meeting the world’s energy needs. At the heart of these systems are solar inverters, the key components that convert the direct current (DC) produced by solar panels into the alternating current (AC) we use in homes, businesses, and the grid. Inverters directly affect overall system efficiency, safety, and longevity. However, like other electronic devices, solar inverters can fail over time for various reasons. These failures may stem from environmental factors (extreme temperature, humidity, dust), electrical stress (voltage fluctuations, lightning), manufacturing defects, or natural component aging. When an inverter fails, energy production stops or degrades, causing significant economic losses. For this reason, fast and accurate diagnosis and professional repair are crucial.
This comprehensive guide examines the most common faulty parts in solar inverters, the root causes behind these faults, and why professional repair processes are indispensable. Our goal is to help anyone searching with keywords such as “IGBT Board fault,” “inverter display board repair,” “DC SPD error,” “capacitor failure,” or “solar inverter power supply repair” access reliable, in-depth information. By explaining each component’s function, fault symptoms, likely causes, and expert repair approaches, we will guide you in keeping your solar energy system running smoothly. This guide aims to be valuable for both technically inclined professionals and end users experiencing issues in their systems.
1. Power Electronics Circuits: The Inverter’s Muscle and Conversion Center
The core function of solar inverters is to convert the DC coming from solar panels into AC used on the grid and in our homes. This critical conversion is performed by power electronics circuits that demand high power and precision. Because these circuits operate under continuous high current and voltage, they contain the most stressed—and therefore most frequently failing—components in the inverter. Overheating, sudden voltage fluctuations, and natural component aging are the main reasons for failures on these boards. Power electronics can be considered the inverter’s heart and muscle; any malfunction here directly impacts the entire system’s performance and reliability. Therefore, proper operation of these components is vital to the inverter’s overall health.
In this section we’ll cover the key elements that perform DC/AC conversion, store energy, step up voltage, and filter signals. Each operates at high power levels and is exposed to thermal and electrical stress. When they fail, they can completely halt production, reduce efficiency, or damage other components. Early detection and professional repair of these board failures are critical for long-life, efficient operation. Our expert teams diagnose faults down to component level in these complex power circuits and provide cost-effective, lasting solutions.
IGBT Board / IGBT Module Faults and Repair
The IGBT (Insulated Gate Bipolar Transistor) board or module is one of the most vital parts of a solar inverter—the switching element in DC-to-AC conversion. It converts DC from panels into AC at grid frequency (typically 50 or 60 Hz) while also switching at high frequencies (in the kHz range). These rapid on/off cycles subject IGBTs to intense thermal and electrical stress. Inadequate cooling (fan failure, dust buildup), overloading (operating above rated power), grid-side voltage spikes (surges, harmonics), or external events like lightning can cause IGBTs to burn, short, or even physically explode. Such failures shut the inverter down, stop production, trip protection fuses, or cause serious system damage. IGBT failures are typically among the costliest and most complex and require expert intervention.
A faulty IGBT Board usually stops the inverter entirely and causes significant production losses. During repair, technicians not only replace the failed IGBTs but also investigate root causes: gate driver issues, insufficient cooling, control board faults, or malfunctions in overcurrent protection that can lead to repeat IGBT failures. Our specialists replace failed IGBT modules with original or higher-grade equivalents, validate driver circuits, and assess cooling efficiency. This minimizes the risk of recurrence and restores original performance and reliability. IGBT repair isn’t just a part swap—it’s a full restoration of system stability and health.
Electrolytic Capacitor Board / DC Bus Capacitors
Electrolytic capacitors on the DC bus store energy and filter voltage ripple. By smoothing DC ripple from panels, they ensure IGBTs are supplied with a clean and stable voltage—critical for efficient, stable operation. Capacitors have a finite lifetime, which is shortened by high temperature, overvoltage, excessive ripple current, and high-frequency operation. Over time, the electrolyte dries out, capacitance drops, ESR (Equivalent Series Resistance) rises, and devices may swell or vent, losing functionality. This visibly degrades inverter performance and can set the stage for failures in other sensitive components.
A faulty Electrolytic Capacitor Board can cause low efficiency, degraded MPPT performance, output voltage ripple, harmonic distortion, and even damage to other power components. You may see low DC voltage, ripple error, overcurrent, or general fault messages on the display. During repair, not only visibly damaged capacitors but all end-of-life electrolytics should be replaced as a set. In our service we use industrial-grade, high-temperature (105°C), long-life, low-ESR capacitors to deliver lasting fixes—improving long-term stability, efficiency, and reliability.
Boost Board (Step-Up Board)
Some inverters—especially those with low input voltage or wide MPPT ranges—include a Boost Board to raise the panel voltage to the DC bus level. Operating at high switching frequencies and currents stresses diodes, inductors, and switching devices (MOSFET/IGBT), which can overheat and degrade over time. A boost failure directly impacts overall performance and energy yield.
A faulty Boost Board can cause low efficiency, MPPT errors, poor processing of PV power, or complete production loss. Typically, power diodes, MOSFETs, inductors, or control ICs are damaged. Repairs involve identifying failed parts and replacing them with original or equivalent-quality components; cooling and drivers are also checked to prevent recurrence. Our experts precisely diagnose Boost Board issues to restore peak efficiency.
DC Filter Board and AC Filter Board
The DC Filter Board attenuates high-frequency noise and harmonics on the PV DC line, delivering cleaner, more stable DC to the inverter. This protects sensitive power electronics and improves efficiency. The AC Filter Board reduces output harmonics and noise so that a cleaner sine wave is delivered to the grid, ensuring compliance with interconnection standards and minimizing interference with other devices. Both filters use inductors and capacitors. Overcurrent, voltage swings, resonance, and aging can overheat and damage these parts.
A faulty DC Filter Board or AC Filter Board leads to inefficient operation, poor power quality (high THD), damage to other power components, or grid interconnection faults. Repairs involve replacing failed filter components with correct values and quality parts. Proper filter operation is critical for inverter lifespan, grid compliance, and electromagnetic compatibility.
Power Supply Board
The Power Supply Board generates multiple DC rails (often 5V/12V/24V) for control boards, drivers, fans, and other low-power electronics. Typically an SMPS, it must run efficiently and reliably. Grid or DC input transients, overheating, aging, or manufacturing defects can cause failures. Common weak points include the SMPS transformer, control ICs, optocouplers, and output capacitors. Failure here can disable the entire inverter.
A faulty Power Supply Board can prevent startup, kill control boards, blank the display, stop fans, or cause unstable behavior—effectively disabling production. Repair includes diagnosing and replacing SMPS components, control ICs, diodes, and electrolytics. Stable PSU operation underpins the entire system; our component-level repairs bring units back to life while avoiding expensive board swaps.
EMC / EMI Filter Board
The EMC/EMI Filter Board reduces electromagnetic noise emitted by the inverter and protects it from external interference, ensuring compatibility with other electronics and compliance (e.g., CE, FCC). High-frequency switching naturally creates EMI; controlling it is critical for reliable internal operation and coexistence with nearby devices. Surges, lightning, overcurrent, or aging can damage inductors, capacitors, or varistors on this board.
A failed EMC / EMI Filter Board can cause excessive emissions, interference with nearby devices, or susceptibility to external noise, leading to instability or disconnection. Repairs typically involve replacing failed inductors, capacitors, and MOVs to restore compliance and reliability.
Driver Board
The Driver Board converts low-power control signals from the main control board into precisely timed, adequately powered gate signals for IGBTs/MOSFETs. Correct gating is essential for efficiency, output quality, and reliability. Overvoltage, overcurrent, thermal stress, noisy control signals, optocoupler faults, or driver IC failures can damage this board, often leading directly to power device failures.
A faulty Driver Board can mistime or fail to trigger IGBTs, causing overheating, shorts, or no operation—often tied to IGBT failures themselves. Repairs involve replacing driver ICs, optocouplers, supply components, and protection diodes. Stable driver operation is vital for a reliable power stage.
Relay Board
The Relay Board houses electromechanical relays that manage the inverter’s grid connection. Relays close when voltage and frequency are within limits and open rapidly during anomalies, providing anti-islanding protection. Frequent switching, high current, arcing, mechanical wear, or coil failures can cause contacts to weld, stick, or fail.
A faulty Relay Board can prevent grid connection (grid fault), cause chattering, or—dangerously—maintain connection during outages (islanding). Repairs replace relays with high-quality, suitably rated industrial parts and verify control/protection circuits to ensure safe, standards-compliant operation.
2. Protection and Safety Circuits: The Inverter’s Armor
Solar inverters don’t just convert energy; they also protect themselves, the PV array, and the grid from electrical anomalies using advanced safety circuits. These protections intervene during overvoltage, overcurrent, short circuits, earth leakage, and lightning events to shield expensive components—preserving your investment and ensuring safety. Any failure here leaves the system exposed to serious damage.
In this section we cover components that harden the inverter against electrical threats and provide a safe operating envelope. Protection parts often sacrifice themselves during surges or faults—that’s their job. Timely, correct replacement is essential to keep the system defended. Our experts identify issues and keep your system aligned with top safety standards.
SPD – DC Surge Protection Board
The DC SPD board is the first and most important line of defense against surges coming from the PV array—especially lightning-induced or grid-related overvoltage events. MOVs or GDTs remain passive during normal operation and conduct within milliseconds during surges, clamping energy and shunting it safely to earth. The SPD may rupture while protecting sensitive, expensive parts (IGBTs, control boards)—a sign it did its job.
A faulty DC SPD Board often triggers “SPD Fault,” “Isolation Error,” or “Varistor Fault.” The inverter may enter protection and halt production. With a failed SPD, the system is unprotected against future surges—risking severe damage. Repairs typically involve replacing the blown module or the entire board with the correct type/rating (Type 1/Type 2). We diagnose DC SPD faults accurately to keep your system continuously protected.
SPD – AC Surge Protection Board
Similarly, the AC SPD protects the inverter’s AC side against grid surges and lightning-induced overvoltages. Switching of large industrial loads, transformer faults, or nearby strikes can inject dangerous transients into the AC line, threatening the inverter and downstream equipment.
A faulty AC SPD Board can cause AC-side issues, grid faults, or damage other AC components. Like DC SPDs, failed AC SPDs must be replaced promptly. We correctly identify and replace both DC and AC SPD modules to ensure full-path surge protection.
Breaker / DC Switch / Isolator
The DC isolator mechanically disconnects PV power from the inverter for safe maintenance, repair, commissioning, or emergencies. Continuous high current can cause internal arcing, melting, or carbonization; loose terminations, low-quality switches, frequent operation, or poor installation can lead to overheating and fire risk.
A faulty Breaker / DC Switch can starve the inverter of energy, reduce performance, or cause terminal overheating and burning odors. Contacts can weld shut—a serious safety risk. Replace immediately with a high-quality, correctly rated device. We diagnose and rectify DC switch issues to keep your system safe and serviceable.
Fuse
Fuses protect circuits from overcurrent. In solar inverters you’ll find them on DC inputs (strings), AC outputs (grid), and internal auxiliaries. During short circuits or overloads, the fuse element melts, opening the circuit to protect costly parts.
A blown Fuse can disable the inverter or a specific path and usually indicates a deeper fault (IGBT short, capacitor failure, cable short). Simply replacing the fuse is not enough—the root cause must be fixed. Use correct types (e.g., gPV for DC). We identify and resolve underlying issues for safe, durable operation.
Varistor / MOV Unit
Varistors (MOVs) form the core of SPD protection, clamping transient overvoltages by dropping resistance above a threshold and absorbing surge energy. MOVs can rupture after doing their job—this is often visible and expected after significant events.
A failed Varistor / MOV Unit leaves the system unprotected against surges. We replace MOVs with correctly rated, high-quality parts to restore surge immunity and extend inverter lifespan.
Earth Leakage Sensor
The Earth Leakage Sensor detects leakage currents to ground—critical for human safety and grounding integrity. Insulation faults, moisture ingress, physical damage, or other electrical issues can create dangerous leakage paths. The sensor triggers shutdown or error codes to protect the system.
A faulty Earth Leakage Sensor can cause false “Isolation Fault/Earth Fault” trips and production loss, or worse, fail to detect real hazards. Repairs include checking the sensor, its wiring, and supply/control circuits and replacing as needed. Proper operation is essential for safety and standards compliance (e.g., IEC 62109-2).
Lightning Arrestor (Surge Arrester)
A Lightning Arrestor protects PV systems against direct or indirect lightning, handling higher energies than standard SPDs and safely shunting currents to earth—vital for large open-field plants.
A failed Lightning Arrestor (often ruptured after a strike) leaves the system vulnerable; it must be replaced and correctly bonded to earth. We identify arrester faults and restore maximum lightning protection.
3. Control and Communication Boards: The Inverter’s Brain and Data Flow
Beyond power conversion, modern inverters include a sophisticated “brain” to manage performance, monitor status, and communicate externally. These low-voltage digital circuits can fail due to software bugs, power disturbances, ESD, or environmental stress—causing misoperation, data loss, loss of remote monitoring, or total shutdown. Reliable control and comms are essential for functionality and manageability.
Here we cover the main control board, measurement/sampling boards, remote communication boards, and the user interface (display). Failures often appear as error codes, display issues, comms dropouts, or bad measurements. Our team repairs these sensitive boards at component level, including firmware reprogramming and recalibration, to keep the inverter technically and operationally sound.
Main Control Board (CPU Board)
The Main Control (CPU) Board is the inverter’s brain, running MPPT algorithms, precisely controlling power stages (IGBTs/MOSFETs), continuously monitoring grid parameters, logging faults, analyzing system status, and handling communications. Microcontroller/processor, RAM/Flash, and peripheral ICs are all critical. Power disturbances, overheating, firmware corruption, ESD, or aging can cause failures that may stop the inverter entirely.
A faulty Main Control Board can prevent startup, cause persistent error codes, block grid connection, or render the unit inoperable. Repairs involve diagnosing and replacing ICs (MCU, memory, comm chips) and reloading firmware/configuration. Our component-level approach often saves the cost of full board replacement.
Sampling Board
The Sampling Board continuously measures key electrical parameters—PV input voltage/current, AC output voltage/current, grid frequency, temperatures—and reports them to the CPU. These data drive MPPT accuracy, grid compliance, protections, and fault detection. Hall sensors or shunts, voltage dividers, ADCs, and signal conditioning reside here. Sensor faults, CT issues, divider errors, calibration drift, or environment can cause malfunction.
A faulty Sampling Board can generate nonsensical errors, unstable operation, low efficiency, or grid faults (e.g., misreading grid voltage causes needless disconnections). Diagnosis requires expertise and precision instruments to isolate the failing channel and recalibrate. We repair at component level and recalibrate to restore accurate, reliable measurements.
Communication Board (RS485 / Wi-Fi / GPRS)
The Communication Board enables remote monitoring and management via RS485, Wi-Fi, Ethernet, or GPRS/4G. It streams production data, sends alarms, and receives remote configuration—crucial for visibility and O&M efficiency. Overheating, firmware issues, network problems, nearby lightning, or simple wear-out can cause failures.
A faulty Communication Board doesn’t usually stop conversion but takes your system offline (“inverter offline,” “communication error,” “no data”), which is operationally painful—especially at scale. Repairs include module/IC replacements, antenna checks, and firmware updates to restore continuous data flow.
ARM Communication Board (Display–CPU Interface)
Some models include a dedicated ARM Communication Board between the CPU and the LCD/Display Board, ensuring correct on-screen data and relaying user inputs back to the CPU. Socket oxidation, line breaks, IC failures, power issues, or ESD can cause faults that disable the local interface.
A faulty ARM Communication Board can blank the screen, show corrupt data, disable keys, or trigger comm errors between display and inverter. Repairs check interconnects, ICs, data lines, and supplies, replacing faulty parts as needed to restore a functional local UI.
Display / LCD Screen Board
The Display Board shows production data, error codes, system status, and other information. It includes the LCD, backlight LEDs, and driver ICs. Outdoor exposure (UV, heat, humidity) and physical stress shorten life; manufacturing defects or connection issues are also common. While a failed display doesn’t stop conversion, it hides status and alarms.
A faulty Display / LCD Screen Board can cause no display, dim/washed text, missing characters, dead backlight, pixel defects, or unresponsive touch. Repairs range from replacing the panel/backlight to changing the entire board, restoring a usable interface.
Keypad / Touch Board
The Keypad/Touch Board lets users navigate menus, change settings, reset faults, and enter commands. Continuous use, mechanical wear, moisture, or dirt can cause sticking keys, lost sensitivity, or failed contacts—especially in outdoor/industrial settings.
A faulty Keypad / Touch Board blocks local control. Repairs replace worn keys/contacts/sensors and verify the interface circuitry so users can reliably operate the inverter again.
RTC (Real Time Clock) Module
The RTC keeps accurate date/time for timestamping energy data, logging events, and running time-based functions (e.g., scheduling). It usually uses a small backup cell (CR2032) to retain time without main power. A dead cell or failed RTC IC breaks timekeeping.
A faulty RTC Module or depleted cell causes wrong timestamps, inconsistent logs, or failed time-based functions. Repairs involve replacing the cell or the RTC IC and validating timekeeping for data integrity and diagnostics quality.
EEPROM / Memory Board
The EEPROM/Memory Board stores configuration, calibration, fault logs, and other persistent data. Flash wear-out (limited write/erase cycles), power disturbances, firmware bugs, or ESD can corrupt memory and destabilize operation.
A faulty EEPROM / Memory Board can force wrong settings, lose logs, hang the boot process, or trigger “Configuration Error/Memory Fault.” Repairs replace memory devices and reload firmware/configuration to restore stable operation.
CAN / Modbus Communication Interface
CAN or Modbus enables integration with EMS, battery storage, other inverters, or SCADA—often via a dedicated board or integrated interface. Transceiver damage, shorts, wiring mistakes, termination errors, or EMI can break communications and disrupt coordination.
A faulty CAN / Modbus Communication Interface stops data exchange and can impair battery charge/discharge control or system coordination (“Communication Error,” “CAN Bus Fault”). Repairs replace transceivers/ICs and verify wiring/termination to restore robust interoperability.
DSP Board (Digital Signal Processor)
The DSP Board in higher-performance inverters generates PWM signals for IGBTs, runs current/voltage control loops in real time, and optimizes dynamic response—improving efficiency, reducing harmonics, and ensuring grid compliance. Firmware corruption, DSP IC failure, overheating, or power issues can take it down.
A faulty DSP Board can produce bad PWM, destabilize the power stage, reduce efficiency, trigger overcurrent/overvoltage errors, or stop operation entirely. Repairs may require replacing the DSP IC and related memory/control parts, reloading firmware, and recalibrating to restore high-quality conversion.
4. Connection and Monitoring Boards: System Integration and Data Collection
Beyond conversion, inverters rely on various connection and monitoring boards to safely collect PV power, deliver it to the grid, and closely observe system performance. These include physical interfaces, current/voltage sensors, and external integration hardware. Overcurrent, loose connections, oxidation, corrosion, or sensor failures degrade functionality and efficiency.
Here we cover input/output terminals, string current monitoring, grounding interfaces, and external comm modules. Failures often appear as power loss, incorrect readings, communication dropouts, or safety alarms. Our technicians precisely diagnose and repair these issues—tightening and refurbishing connections, replacing sensors/terminals—so your system runs safely and at peak efficiency.
DC Combiner Current Board (Positive / Negative)
The DC Combiner Current Board is crucial in systems with multiple PV strings. It safely combines each string’s current into a single inverter input and can also perform String Monitoring by measuring each string’s current individually. This enables tracking of per-string performance and rapid detection of issues (shading, panel failure, connection faults). High currents stress the board’s Hall sensors or shunts, terminals, and protection parts, leading to overheating, sensor failure, loose lugs, or oxidation.
A faulty DC Combiner Current Board can block a string’s power from reaching the inverter, misreport currents, or trigger “String Fault/Low Current” errors—reducing system yield. Repairs include checking and replacing sensors and terminals and inspecting protection diodes and fuses to restore accurate, reliable string monitoring.
Terminal Block / Connector Board
The Terminal/Connector Board provides all electrical interfaces (DC input, AC output, comms, grounding). It includes screw terminals, spring clamps, MC4s, and specialty connectors. Loose or poorly torqued connections, oxidation/corrosion, moisture ingress, overcurrent, or physical damage can cause overheating, arcing, resistance losses, and fire risk—jeopardizing performance and safety.
A faulty Terminal Block / Connector Board causes interruptions, losses from high resistance, “Connection Fault” errors, or safety hazards (e.g., DC arcing). Repairs replace damaged terminals/connectors or the board itself and retorque/clean all lugs to spec for safe, efficient operation.
AC Output Board
The AC Output Board routes converted AC to the grid or loads and houses related protection (AC fuses, AC SPD, relays). Compliance with interconnection standards (e.g., EN 50438, VDE-AR-N 4105) is essential for safety and grid stability. Overcurrent, shorts, grid disturbances, frequency drift, or loose connections can cause failures that directly affect export capability.
A faulty AC Output Board can prevent grid export, trigger “Grid Voltage/Frequency Out of Range,” or repeatedly disconnect. Repairs include replacing faulty connections, fuses, relays, and checking grid-monitoring circuits to restore safe, continuous export.
DC Input Board / PV Terminal
The DC Input Board/PV Terminal is where PV strings connect to the inverter, typically including MC4 inputs, protection diodes, fuses, and sometimes sensors. It must safely deliver high DC voltage/current. Reverse polarity, loose lugs, oxidation, corrosion, overcurrent, lightning, or physical damage can cause failures that halt production or create hazards.
A faulty DC Input Board / PV Terminal can block a string, create losses from high resistance, or trigger “PV Isolation Fault,” “DC Overvoltage,” or “DC Low Voltage.” Loose MC4s can arc and burn, damaging panels and inverter. Repairs replace damaged terminals/connectors/diodes or the board itself and retorque/clean all inputs to spec.
String Monitoring Board
The String Monitoring Board—especially in utility-scale and commercial plants—measures each string’s current and voltage for real-time performance tracking, rapid detection of underperforming strings (shading, panel fault, soiling, connection issues), and timely maintenance. Its precision sensors and comms ICs continuously collect data and report it to the main control or a remote system for analytics and alarms.
