Knowledge of LED power supply usage
Impact of overload on LED power supply life
When the power of the connected lamp exceeds the maximum output power of the LED power supply, the following phenomena will occur:
1. When the maximum output power of the power supply is exceeded (generally 5%-15%), the power supply will be protected and an abnormal state of intermittent switching will occur. If it is in this state for a long time, the life of the power supply will be shortened or even damaged.
2. When the lamp's power exceeds the power supply's maximum output power, the power supply's internal temperature will rise. The switching power supply is an electronic product. The life of electronic products depends to a large extent on the maximum operating temperature. The higher the temperature, the shorter the life. In addition, the power supply itself also consumes energy, which is specifically manifested as heat.
Therefore, during installation and use, it is necessary to avoid overloading the power supply. It is recommended that the load power be 80% of the power supply output power. Only by reducing the body temperature can the life of the power supply be extended.
Distinguish and confirm the input and output of the LED power supply, and the hazards of reverse wiring
1. The power supply consists of basic components such as input components (wires), body, and output components (wires). During installation, you must know the input and output ends of the power supply to ensure the correctness and safety of the installation.
(Based on our company's products) How to distinguish the input and output positions of the LED power supply:
A. Confirm from the content of the sticker that the side showing the words "INPUT" or "input" indicates the input end, which is connected to the grid (AC) voltage, and the side showing the words "OUTPUT" or "output" indicates the output end, which is connected to the lamp.
B. When the LED power supply uses electronic wires: the input wire is double white, the yellow-green alternating wire is the ground wire, the output wire is brown or red for the "+" wire, and the blue or black for the "-" wire.
C. When the LED power supply uses sheathed wires: the black sheathed wire is the input end, and the yellow-green alternating wire is the ground wire. The white sheathed wire is the output end, the brown output core wire is the "+" wire, and the blue output core wire is the "-" wire.
2. When the input and output ends of the LED power supply are reversed, the components' withstand voltage in the power supply's output circuit is much lower than the mains voltage, causing the components to break down instantly, forming a large short-circuit current. In mild cases, the copper foil and components of the entire output end of the power supply will burst violently. In severe cases, the live wire and the neutral wire of the mains will be short-circuited directly, causing the wires to burn out and even cause a fire.
Three-phase LED power supply neutral line configuration
For switching LED power supplies with a power factor of 0.4-0.6, when multiple power supplies are configured in a balanced manner in a three-phase four-wire system, the current on the neutral line cannot be offset due to the distortion of the input current waveform. Therefore, in general, it is recommended to set the specification of the neutral line to more than 1.5-2 times that of the phase line and configure it in the maximum measured current mode.
Why is it not allowed to install a fuse (air switch) on the neutral line of a three-phase four-wire lighting circuit, while a fuse (air switch) must be installed on a single-phase two-wire lighting circuit?
In a three-phase four-wire 380/220 volt neutral point grounding system, if a fuse is installed on the neutral line, when the fuse blows, if the three-phase load on the line behind the breakpoint is unbalanced, a higher voltage will appear in the phase with less load, causing an accident of burning out the equipment, especially when single-phase grounding occurs, the situation is more serious. Therefore, a fuse cannot be installed on the neutral line.
For the 220 two-wire lighting power supply line used in life, most people who are not familiar with electricity often come into contact with it, and sometimes when repairing and extending the line, the phase line and the neutral line are often connected incorrectly. In addition, for this kind of line, even if the neutral line is broken, it will not cause an accident or burn out the electrical equipment, so a fuse is installed on the neutral line.
How to eliminate the influence of the power supply's floating voltage on the controller?
During operation, the LED power supply's input AC voltage is sensed at the output end, so the output DC voltage of the power supply contains an AC component voltage. This AC voltage is called floating voltage, also called induced voltage. In some LED power supplies, this floating voltage may be as high as more than 100 volts, confusing the controller's chip program or even damaging it.
Inrush current and closing margin
When the LED power supply is started, a short-term inrush current will be formed on the power input line. The instantaneous peak of the inrush current is about 5 times the LED power supply's rated current. When selecting a switch, you need to select the closing current margin. For example, when the circuit's normal current is 10A, the switch's working current should be around 15A-20A to ensure that the switch can close normally.
High current connection method and precautions
In the installation of high current lines, it should be noted that the connection between the power lines must have sufficient mechanical strength, the largest contact area, and ensure good contact. (For example: use high current terminals and fix them with screws)
If the power line has poor contact or insufficient mechanical strength, it will cause arcing (discharge) between the connection terminal and the wire, causing an oxide layer to appear on the terminal and the wire, which in turn exacerbates the arcing situation. Under this vicious reaction, the wire and the terminal will eventually be disconnected.
