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LED display power supply is too large how to deal with
LED displays often experience a situation where the neutral line current is higher than the phase line current. This phenomenon is typically caused by the switching power supply used to power the LED display, which generates a significant amount of third harmonic current.
In a balanced three-phase system, the currents are evenly distributed and have a 120-degree phase difference. As a result, they cancel each other out, and the neutral line current should ideally be zero. However, the switching power supply introduces a third harmonic current that is a zero-sequence current, meaning it has the same phase angle in all three phases. This causes the harmonic currents to add up on the neutral line, increasing its current significantly.
The third harmonic current from a switching power supply can range between 55% and 80% of the total current, leading to unusual conditions such as "phase current being much smaller than neutral current" or "neutral current close to the sum of the phase currents."
To address this issue, a dedicated zero-sequence filter (ZSFGD series) is an effective solution. It is specifically designed to handle the high neutral current caused by LED displays. This technology uses advanced methods to detect and cancel the third harmonic current, reducing the neutral line current effectively. The zero-sequence filter is connected in parallel with the phase lines of the LED display. When the third harmonic current passes through, the filter generates opposing magnetic flux, which cancels out the harmonic and reduces the neutral current.
Using a zero-line overcurrent filter offers several benefits:
1. It can reduce the neutral line current of the LED display by 90% or more.
2. It helps prevent overheating of cables, reduces energy losses, and saves 3% to 8% in electricity costs.
3. It prevents insulation aging on the neutral wire, reducing the risk of electrical fires caused by short circuits.
The ZSFGD type zero-sequence filter has several advantages compared to traditional solutions like neutral current blockers:
1. **Installation**: Neutral current blockers require the main switch to be turned off for installation, while the zero-sequence filter can be installed without interrupting the LED display.
2. **Compliance**: Neutral current blockers may not meet national standards, as they are not allowed to be connected in series on the neutral line. Zero-sequence filters comply with all relevant regulations.
3. **Safety**: Neutral current blockers can carry voltage, posing an electric shock risk. In contrast, zero-sequence filters do not have voltage on the neutral line, making them safer for human contact.
4. **Device Safety**: If a neutral current blocker fails, the LED display loses its neutral connection, potentially damaging the screen. A failed zero-sequence filter will only stop the display from starting, without causing damage.
5. **Short Circuit Safety**: A short circuit in a neutral current blocker increases the impedance of the neutral line, reducing the short-circuit current and potentially causing a fire. A zero-sequence filter allows the circuit breaker to trip safely.
6. **Effectiveness**: Neutral current blockers typically filter less than 60% of the neutral current, while zero-sequence filters can filter over 90%.
By using a zero-sequence filter, you can ensure the safe and efficient operation of your LED display while protecting both the equipment and the electrical system.