Cable Cross-Sectional Area Calculation and Selection for LED Displays
The core of cable selection for any LED display board, large LED display screen, or modular system is based on the maximum power. Key considerations for LED display manufacturers, suppliers, and installers are:
Power Calculation Basis: The actual power consumption when playing video is ~1/3 of the maximum (white balance). However, cable sizing for the LED screen display must use maximum power for safety.
Special Neutral Wire Requirement: If the LED display screen or modular
LED display panels do not mitigate the 3rd harmonic, the neutral current can exceed twice the phase current. The cable must then be sized for this neutral current, preferring a 4+1 core cable.
Maximum Power Calculation: Calculate by summing the max power of each LED screen panel or 4 digit LED display module, or by estimating based on the total number of switching power supplies in the display screen.
Main Circuit Breaker Leakage Protection Configuration
LED displays are industrial products. LED display factories, importers, and distributors must note that residential-grade leakage protection is unsuitable.
Main Breaker Setting: Total leakage current for an LED display often exceeds 30mA (residential standard). For every 100m², it can be >100mA. Use an adjustable leakage protection breaker (100mA/300mA/500mA) for line safety.
Branch Circuit Protection: For personal safety priority (e.g.,
LED screens for events or an LED screen for a Party), configure 30mA leakage protection on each output.
Key Points for International Power Calculation
LED display suppliers and manufacturers must adapt to local standards:
Common Voltages: Inputs: 3-phase 220V/380V. Outputs: single-phase 110V/220V.
Rule Adaptation: For a 3-phase 220V 5-wire system, the output power is half of an equivalent Chinese 380V system. A 3-phase 220V 3-wire system requires a specialized design.
Comparison of Harmonic Elimination Methods
Switching PSUs in LED panels generate harmonics during AC/DC conversion. The 3rd harmonic significantly impacts the neutral wire.
Harmonic Eliminator: Traditional, bulky, with limited applicability.
PFC Power Supply: Higher cost, variable effectiveness; neutral current may still be high.
DC Power Solution (Preferred): Supplying DC48V directly from the distribution box eliminates harmonics at the source. This is key for power quality, especially for complex flexible LED display modules and high-density screens.
Condensation Treatment for Outdoor Installations
Common in northern outdoor scenarios for large outdoor LED screens or large LED screens for stage. The internal temperature drop after shutdown causes condensation.
Solution: Fans continue for 1 hour post-shutdown to equalize temperature and prevent water droplets, crucial for large LED screens for churches and outdoor installations.
Lightning Protection Measures
Power SPD: Class C, ≥40KA capacity.
Signal SPD: For network, 485, audio lines.
Lightning Rod: Atop the screen structure for direct strike protection.
Selecting D-type Circuit Breakers
LED display panels often use 200W (5V/40A) switching PSUs with high inrush current. D-type breakers (10x threshold) prevent nuisance tripping, making them ideal for distribution box outputs.
Why No Leakage Protection on Main Breaker?
PSU Leakage: A standard 200W PSU has <1mA leakage. PFC types offer wider input (110V-220V) and higher power factor (0.96 vs. 0.6).
Cumulative Effect: A 20KW screen (100 PSUs) can have ~200mA total leakage. A 30mA residential breaker would trip constantly.
Applicable Scenarios for Leakage Protection
Can be used in LED display distribution boxes if:
Main breaker is an adjustable industrial-grade unit (e.g., 100mA-300mA).
Branch circuit power is ≤3.5KW (≤20 PSUs), allowing 30mA protection for personnel safety.
Output Breaker & Wiring Specs
Breaker: For capacitive PSU loads, use D25A or D32A for margin, even if D20A is theoretically sufficient.
Wiring: Use 2.5mm² copper wire (25A capacity), suitable for standard 3.5KW (16A) branches.
Power Distribution Box Classification
Protection Level: IP43 (Indoor), IP55 (Outdoor).
Control Method: Manual, Timer, Multi-card, PLC, 433/LoRa/APP/CLOUD wireless.
Power Specs: 10KW-300KW range. Typically 3 outputs per 10KW, using RVV-3×2.5mm² cable.
New Fire Detection: "Smoldering Protection"
This technology detects thermal particles in the very early smoldering stage (before smoke), providing hours of advance warning—superior to traditional smoke alarms for proactive hazard prevention.
Harmonic Hazards and Countermeasures
Overview of Harmonic Hazards
Neutral current exceeding phase current is a critical hazard in LED display power systems. Lack of neutral overcurrent protection can lead to overheating, fire, and accelerated aging of transformers/cables.
Causes of Excessive Neutral Current
Core Cause: 3rd harmonic from PSUs, causing neutral current ~2x phase current.
Secondary Cause: Unbalanced 3-phase loads during dynamic content playback.
Example: A 200KW large LED screen at full load: Phase current ~300A, Neutral current ~600A. The neutral cable may need to be doubled in size. Screens >100m² should strongly consider a neutral current eliminator.
Main Hazards of Harmonics
Safety Risk: Neutral wire (typically 1/3-1/2 phase size) overheats, risking short circuits and fire.
Energy & Equipment: Wasted energy, transformer protection trips, capacitor damage, lower power factor, higher costs.
Malfunction: Switch failures, reduced stability, shorter component life.
Manifestations of Harmonics
Neutral current ~2x phase current.
Persistent neutral cable heating.
Contactor hum, varying with screen content (loudest on white).
Harmonic Treatment Methods
Install a harmonic elimination module.
Use PFC switching power supplies.
Adopt a DC power supply scheme (DC48V/DC280V).
Increase neutral cable diameter.
Advantages & Trends of DC Power Distribution
As Mini/Micro LED and innovative screens (flexible LED display module, transparent screens) trend towards thinner, higher-density designs, the drawbacks of traditional AC-DC conversion (harmonics, bulky PSUs) are magnified. DC power (mainly DC48V) is becoming mainstream.
Eliminates Harmonics: Neutral current <25% of phase current, optimizing quality.
Enables Special Designs: For transparent, grid, or film screens, external PSUs are eliminated, allowing thinner, more aesthetic LED display boards.
Current Sharing Protection: If one PSU in a redundant group fails, others share the load, ensuring the LED display screen operates uninterrupted. This is a key advantage offered by advanced LED display manufacturers for reliable best LED large screen solutions.
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