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The power consumption of an electrical appliance is calculated based on its electrical power. To calculate this, multiply the current by voltage.

In actual usage, power calculations divide loads into two categories: resistive load and inductive load.

This article will guide you the details of LED display power consumption, cable size and other related issues.

**Calculating the resistive load****: **P = UI, i.e. power = voltage x Current

**Calculating inductive loads****: **P=UIcosf – that is power = voltage * current * power factor

LED display screen is an inductive power load that is powered by switching power supply. Cosf = 0.75 is the power factor for its switching power supply. Power factors are different for inductive loads. We can use a power factor of 0.8 when calculating the power supply for the LED display switching supply.

The driving voltage of LED display screen is 5V and its driving current is under 20mA. Calculate the maximum power of a screen (based on a 100-square-meter area) as follows:

Imagine the following: the pixel pitch of the outdoor LED display is 10mm; the pitch density is 10,000 pixels/square meter; each point is composed of three LED lights – one red, one green, and one blue – and the scanning is 1/4 scan.

Calculation of LED display Power per Square Meter: P = 10000 (dots).

The total power consumption for the LED display screen is: P=750 (W) * 100 (square meters) =75KW

**The power consumption of the whole**** LED**** screen**

Due to losses in the conversion of electric energy, 10% is added on top of the calculated theoretical value. Auxiliary equipment (air conditioners and fans) and lighting, amplifiers, and other devices also consumes some electricity. Calculate the power consumption of auxiliary equipment for the LED screen based upon the actual amount.

P= 75KW+7.5 KW +5KW =87.5KW

The maximum current of the display is:

I=P/Ucosf=87500(watt)/220*0.8(cosf)=318(A)

Under normal conditions of operation, however, LEDs cannot be light up for long periods. If the power supply capacity of the user is low, then a formula based on a common coefficient can be used. The common coefficient in this case is usually 0.5. The above calculation is rewritten to:

I=P*Public coefficient/Ucosf=(82500 (watt)*0.5+5000 (watt))/220*0.8 (cosf)=168(A)

The total current of this LED display is 168A. Because the instantaneous current when the LED display is started is relatively large, the three-phase 168A switch cannot be used for the main air switch.

It is recommended to use a 318A air-switch, but 400A will suffice. Our fellow engineers are used to calculating the power of large displays by using the number switching power supplies across the LED screen. This method is not standard. Some manufacturers cut the number of switching supplies to save money, but this leads to inaccurate power calculations.

**Average power consumption:**

Power consumption is affected by the type of content that’s being played. When playing advertisements, which are mainly white and rich in colors, the average consumption of power is 50%. However, when simple graphics, such as text or images, are displayed, the majority of the LED screen will be black and the average consumption of power is 10%. Normal advertising statistics show that the average power usage is usually 40% of the maximum.

The general method for calculating the safety of copper wire is:

The maximum safe current carrying capacity of 2.5 millimeter copper cable is 28A.

The maximum safe current carrying capacity of 4 millimeter copper cable is 35A.

The maximum safe current carrying capacity of 6 millimeter copper cable is 48A.

The maximum safe current carrying capacity of 10 millimeter copper cable is 65A.

The maximum safe current carrying capacity of 16 millimeter copper cable is 91A.

The maximum safe current carrying capacity of 25 millimeter copper cable is 120A.

Aluminum wire should have a diameter 1.5-2 times greater than copper wire.

It is safe to use 10A per sq. millimeter if the current in copper wire is less than 28A.

If the copper wire is more than 120A in current, multiply it by 5A per square mm.

You can select the current that the conductor’s cross-sectional area can normally carry based on the number of currents you need to conduct. It can be estimated by using the following experience.

if you remember that copper wires with a diameter of less than 6 square millimeters for indoors are safe if the current per square meter does not exceed 10A. From this perspective, you can choose 1.5 square meters of copper wire or 2.5 square meters of aluminum wire.

The wire current density should be 6A/mm2 within 10 meters. This is the most suitable. The wire current density should be 3A/mm2 for 10-50 meters. 50-200 meters is 2A/mm2. Above 500 meters it should not exceed 1A/mm2.

If it’s not too far, you can use 4 square meters copper wire, or 6 square metres aluminum wire. If the power source is 150 meters away, regardless of whether it’s a high-rise or not, 4 square meters copper wire is required.

The impedance is directly proportional with the length of a wire and inversely related to its diameter. Pay attention to the wire diameter and material of input and output wires when using a power supply. Preventing excessive current from heating the wires, causing accidents.

This table shows the diameter of copper wires at various temperatures and their maximum current.

Cable size/temperature/A | 60 | 75 | 85 | 90 |

2．5 | 20 | 20 | 25 | 25 |

4．0 | 25 | 25 | 30 | 30 |

6．0 | 30 | 35 | 40 | 40 |

8．0 | 40 | 50 | 55 | 55 |

14 | 55 | 65 | 70 | 75 |

22 | 70 | 85 | 95 | 95 |

30 | 85 | 100 | 100 | 110 |

38 | 95 | 115 | 125 | 130 |

50 | 110 | 130 | 145 | 150 |

60 | 125 | 150 | 165 | 170 |

70 | 145 | 175 | 190 | 195 |

80 | 165 | 200 | 215 | 225 |

100 | 195 | 230 | 250 | 260 |

The diameter of the wire is calculated using this formula: Copper wire S= IL/ 54.4*U

Aluminum wire: S= IL / 34*U`

In the formula, I is the maximum current that can pass through the wire.

The length of the wire is measured in M.

U `—- Allowable power supply drops (V)

S —-Cross sectional area of conductor (MM2):

The U voltage can be chosen based on a range of equipment, such as detectors, used throughout the entire system. Also the voltage rating for the power supply used to power the whole system.

The maximum current safe to be charged by three-phase power is three times that of the previous calculation. Therefore, the 25-square meter four-wire, three-phase cable (4+1), which is the national standard and can be used. A cumulative discount calculation will be required if the cable wiring is longer than a specified length, is located in an environment with high temperatures, or is concealed.

Otherwise, it could affect normal usage and cause the cable heating up. Circuit breakers without graded power supplies should also be replaced every 5 years. Frequent switching of current and voltage will result in electric shocks and premature aging. This leads to poor contact between the circuit breakers. Electrical fires can occur if the above items are not taken serious.