First, problems with LED display screens:
1. The light current of the LED display is too large (between 1.6 and 2.4 times of the current phase of the zero-line current);
2. The noise of LED screen cable is large and the zero line heating is serious.
3. LED screen tripping (leakage switch or circuit breaker).
Second, the reason of the high current ratio of LED display is larger than phase line current
Three phase current equilibrium, three phase current vector Angle difference of 120 degrees, three phase can cancel each other, zero line current is zero.
LED display for switch power supply, switching power supply much on the grid (three times of harmonic current) due to 3rd harmonic current, for zero sequence current Jie wave due to 3rd harmonic current, three-phase vector Angle is consistent, so three superposition of harmonic power flow to the zero line.
Usually 3 times of switch power supply harmonic current content is between 55% ~ 80%, the LED display screen appear some strange phenomenon: “the phase line current is smaller than zero line current many/zero line current is close to the sum of the phase line current”
Third, the solution of the high current of zero line
LED display special zero – sequence filter (ZSFGD series) is one of the best practices in the field of the power generation of LED display. It is the best product to solve the excessive line current caused by LED screen.
Zero sequence filter and LED display line in parallel connection, through the zero sequence filter due to 3rd harmonic current, zero sequence filter can produce magnetic flux, after calculation, through testing the device in the opposite direction from the internal to create equal/offset magnetic flux, so as to filter out, due to 3rd harmonic current to eliminate the zero line current
fourth. What are the benefits of the zero-line overcurrent filter
1. Can reduce the current of the LED display line 90% or more;
2. Avoid the scalding of cable wires and reduce losses, and save 3% ~ 8% of the electricity bills as a whole;
3. Avoid the aging of the insulation thread, which causes the electric fire to be short-circuited.
fifth. The characteristics of the zero line overcurrent filter
Taking ZSFGD zero-sequence filter as an example, the following features are compared with traditional solutions (zero-line current interrupters).
1. Installation method: zero-line current interrupter is connected to the zero line, and the installation of the transformer total switch power failure, zero sequence filter and the three-phase four line is installed.
2. National standard: zero-line current interrupters do not meet the national standards, and the rule/zero sequence filter that does not allow any device to connect to any device is in line with all national standards;
3. Personal safety: the zero line current interrupter has the voltage on the zero line, the contact with the zero line has the electric shock hazard/zero sequence filter zero line no voltage, and the person is not in danger of contact with the zero line;
4. Safety of the display device: zero line current interrupter device is damaged, the display is not zero, the electronic components of the display are damaged, the screen is broken, the screen is not electric, and it cannot be started;
5, electrical short circuit safety: zero line blocking device inside the screen short circuit current, due to the zero line impedance becomes larger, the decrease of short-circuit current, the leakage time longer, the superior switch don’t trip surface caused by electrical fire/zero sequence filter in internal short circuit, display superior switch normal protection tripping, there is no danger.
6. Zero line current elimination effect: zero – line current filter rate of zero – line current filter is lower than 60% / zero sequence filter zero – line current filtration rate is higher than 90%.