Explanation of the power supply knowledge required for LED

1. What is mains electricity? That is, what we commonly refer to as alternating current (AC), AC power consists of three components: voltage, current, and frequency. Its frequency is divided into 50Hz and 60Hz, and the voltage distribution ranges from 100V to 240V. Domestic mains electricity is generally 50Hz and 220V, and the normal waveform of AC power is a sine wave.

2. What is three-phase electricity? A power source with equal amplitude, equal frequency, and a phase difference of 120 ° is called three-phase electricity.

3. The voltage between phases is called phase voltage. The phase voltage in mains power is 308V. In fact, three-phase power not only has 380V, but also 10KV, 35KV, 110KV, 220KV, and 500KV. The voltage between the phase and the centerline is the line voltage, which is 220V.

4. Power factor

This value is usually between 0.5 and 1, and its absolute value cannot be greater than 1. It is the ratio between the actual power (W) and the consumed power (VA). A higher ratio indicates better efficiency, usually greater than 0.8, with the larger the better.

Characteristic parameters of power transformers

(1) Working frequency: 50Hz

(2) Rated power: The output power of a transformer that can operate for a long time without exceeding the specified temperature rise at the specified frequency and voltage.

(3) Rated voltage: refers to the voltage allowed to be applied to the coil of a transformer, which must not exceed the specified value during operation.

(4) Voltage ratio: refers to the ratio of the primary voltage to the secondary voltage of a transformer, with differences between no-load voltage ratio and load voltage ratio.

(5) No load current: When the secondary of a transformer is open circuited, there is still a certain amount of current in the primary, which is called no-load current. The no-load current is composed of magnetizing current (generating magnetic flux) and iron loss current

Composed of iron core loss. For a 50Hz power transformer, the no-load current is essentially equal to the magnetizing current.

(6) No load loss: refers to the power loss measured at the primary level when the secondary of the transformer is open circuit. The main loss is iron core loss, followed by the loss caused by no-load current on the copper resistance of the primary coil

(Copper loss), this part of the loss is very small.

(7) Efficiency: refers to the percentage of the ratio of secondary power P2 to primary power P1. The higher the rated power of a transformer, the higher its efficiency.

(8) Insulation: Refers to the insulation performance between the coils of a transformer and between each coil and the iron core. The insulation resistance is related to the performance of the insulation material used, temperature, and humidity level.