# Power consumption and cable calculation of the hot

2022-07-22
• Detail

Dry goods: power consumption and cable calculation of LED display screen

this paper has specially sorted out the knowledge about the power consumption of display screen and the cross-sectional area of cable

about the power consumption of the display screen and the cross-sectional area of the cable, this article has specially sorted out the knowledge in this regard. We calculate the power consumption of electrical products based on their electric power, that is, how much "work" the appliance does per hour, and this work is obtained by multiplying the current by the voltage

however, in practical use, power calculation generally includes two types of loads, one is resistive load, and the other is inductive load

calculation formula for resistive load: p=ui, i.e. power = voltage × Calculation formula of current

for inductive load: p=uicos ф， I.e. power = voltage × electric current × Power factor he is more willing to seek the expansion of the range under stable conditions

and our LED display screen is used through switching power supply voltage transformation, which belongs to inductive load. Power factor cos of switching power supply load ф= 0.75。 The material has elasticity and wear resistance with different inductance. The load power factor is different. We can calculate the power factor cos when the LED display is powered by the switching power supply ф Take 0.8

5v is selected as the driving voltage of LED display screen, and the driving current is less than 20mA, then the maximum power calculation method of the screen body is as follows (based on 100 square meters):

1. The specification of outdoor LED display screen is: the point spacing is 10mm, the point density is 10000 points/square meter, and each point (pixel) is composed of three LED lights, one red, one green and one blue. The scanning method is 1/4 scanning

2. Power calculation of display screen per square meter: p= 10000 (points) x 3 (PCS) x 5 (V) x 0.02 (a) x 1/4 (scanning) =750 (W)

3. Power consumption of the whole display screen: p= 750 (W) X100 (M2) =75kw

4. Power consumption of the whole screen:

because of the product loss of mutual conversion of electric energy, the general power is increased by 10% on the basis of the theoretical calculation value. Auxiliary equipment (air conditioner, fan, lighting, power amplifier, etc.) between panels also generate certain power consumption. The power consumption of auxiliary equipment of this panel is calculated according to the actual amount (we calculate the following formula as 5kW temporarily)

p= 75kw+7.5 kW +5kw =87.5kw

therefore, the total power of the display screen is 87500 watts, and the maximum current is:

i=p/ucos ф= 87500 (W) ÷ 220*0.8 (COS ф）= 318 (a)

however, under normal working conditions, the LED of the display screen cannot be lit for a long time at the same time, so a common coefficient formula can be used when the user's power capacity is small, and the common coefficient is generally 0.5. Therefore, the above calculation should be rewritten as:

i=p* common coefficient/ucos ф= (82500 (W) *0.5+5000 (W)) ÷ 220*0.8 (COS ф）= 168 (a)

that is, the total current value of this screen is 168a. Because the LED shows that the instantaneous current is relatively large when starting, the three-phase 168a switch can not be used for the air switch of the main switch. Instead, the 318a air switch should be used, and 400A can be used. Many of our engineers in the same trade habitually calculate the total power of large screen directly by the number of switching power supplies on the whole screen. This method is not standard. Some manufacturers reduce the number of switching power supplies in order to reduce costs, which eventually leads to power calculation errors

5. Average power consumption:

power consumption varies due to different playback contents. For example, advertising videos are rich in color, mostly white, and the average power consumption is 50% of the maximum power consumption; When playing simple graphics such as text, most of the screen is black, and the average power consumption is 10% of the maximum power consumption. According to the statistics of normal advertisements, the average power consumption is generally 40% of the maximum power consumption

the general copper wire safety calculation method is:

2.5 mm2 copper power line safety current carrying capacity - 28a

4 mm2 copper power line safety current carrying capacity － 35A

6 mm2 copper power line safety current carrying capacity － 48A

10 mm2 copper power line safety current carrying capacity - 65A

safety current carrying capacity of 16 mm2 copper power line － 91A

25 mm2 copper power line safety current carrying capacity － 120a

in case of aluminum wire, the wire diameter shall be 1 Times

if the current of copper wire is less than 28a, take 10A per square millimeter to ensure safety

if the copper wire current is greater than 120a, take 5A per square millimeter

the current that can normally pass through the cross-sectional area of the conductor can be selected according to the total current it needs to conduct. Generally, it can be determined according to the following doggerel:

ten lower five, one hundred upper two, two five three five four, seventy-nine five times and a half, and the copper wire is upgraded

let me explain to you that for aluminum wires with an area of less than 10 square meters, multiply the number of square millimeters by 5. For copper wires, it is necessary to raise the gear. For example, for copper wires with an area of 2.5 square meters, it is calculated as 4 square meters The cross-sectional area of more than 100 is multiplied by 2, that of less than 25 square meters is multiplied by 4, that of more than 35 square meters is multiplied by 3, and that of 70 and 95 square meters is multiplied by 2.5. These words should be easy to remember.

note: they can only be used as estimates, not very accurate. In addition, if you remember the copper wire with less than 6 mm2 of wires indoors, it is safe that the current per square meter does not exceed 10A. From this point of view, you can choose 1.5 m2 of copper wire or 2.5 m2 of aluminum wire

10m, conductor current density 6a/mm2 is appropriate, m, 3a/mm2, m, 2a/mm2, and less than 1a/mm2 above 500m. From this point of view, if it is not very far away, you can choose 4 square copper wire or 6 square aluminum wire. If the power supply is really 150 meters away (not to mention whether it is a high-rise building), it must use 4 square meters of copper wire

the impedance of the conductor is directly proportional to its length and inversely proportional to its diameter. Please pay special attention to the wire and diameter of input and output wires when using the power supply. To prevent accidents caused by overheat of conductor due to excessive current

the following table shows the wire diameter and the maximum current that the copper wire can withstand under different temperatures

wire diameter (approximate value) (mm2) copper wire temperature (Celsius) current (a) 2...

wire diameter is generally calculated according to the following formula: copper wire: s= IL/54.4*u`

aluminum wire: s= IL/34*u`

where: I - maximum current passing through the wire (a)

l - length of the wire (m)

u` - allowable power drop (V)

s - sectional area of the wire (mm2) Description:

1 The u'voltage drop can be selected by comprehensively considering the power supply voltage rating distributed to the system by the equipment (such as detectors) used in the whole system

2. The calculated sectional area is upward

estimation of ampacity of insulated conductor the multiple relationship between ampacity of aluminum core insulated conductor and section conductor section (mm2) 11.52.95120

ampacity is the multiple of section 9876543.532.5

ampacity (a) 9142332486090100123150210238300

estimation formula: multiply two points five by nine, and go up minus one. Thirty five times three and a half, two groups minus five. The conditions are changed and converted, and the high-temperature copper is upgraded. Through the pipe root, it has full functions and expandability. It has a high number of 234 and 876 fold full load flow. Note: (1) the formula in this section does not directly point out the current carrying capacity (safety current) of various insulated wires (rubber and plastic insulated wires), but is expressed by "multiplying the section by a certain multiple", which is obtained through mental calculation. It can be seen from table 53 that the multiple decreases with the increase of the section. "Multiply 2.5 times 9, and decrease 1 to go in sequence" refers to aluminum core insulated wires with various sections of 2.5mm 'and below, and their current carrying capacity is about 9 times the number of sections. For example, the current carrying capacity of 2.5mm 'conductor is 2.5 × 9＝22．5(a)。 The multiple relationship between the ampacity and the number of cross sections of conductors from 4mm 'and above is arranged upward along the line number, and the multiple is reduced by L, i.e. 4 × 8、6 × 7、10 × 6、16 × 5、25 × 4。 "Thirty five times three and a half, two groups minus one and a half", which means that the current carrying capacity of 35mm conductor is 3.5 times of the number of sections, that is, 35 × 3．5＝122．5(a)。 For conductors of 50mm 'and above, the multiple relationship between the ampacity and the number of sections becomes a group of two wire numbers, and the multiple is reduced by 0.5 in turn. That is, the current carrying capacity of 50 and 70mm 'conductors is 3 times the number of sections; The carrying capacity of 95 and 120mm "conductors is 2.5 times of their sectional area, and so on. "Conditions are changed and converted, and high temperature copper is upgraded at 10% discount". The above formula is determined by the aluminum core insulated wire and exposed laying at the ambient temperature of 25 ℃. If the aluminum core insulated wire is exposed in the area where the ambient temperature is higher than 25 ℃ for a long time, the conductor ampacity can be calculated according to the above formula, and then 10% discount can be given; When copper core insulated wire is used instead of aluminum wire, its current carrying capacity is slightly larger than that of aluminum wire of the same specification. The current carrying capacity of one wire number larger than that of aluminum wire can be calculated according to the above formula. For example, the current carrying capacity of 16mm 'copper wire can be calculated as 25mm2 aluminum wire

according to the previous calculation of 318a of the total current of the 100 square meter display screen, the maximum safe current of the three-phase electricity with load is 3 times of the above, so the national standard 25 square three-phase five wire (4+1) cable can be used normally. If the cable wiring exceeds a certain length, or in high temperature environment, or concealed laying, the accumulated discount calculation is required. Otherwise, the normal use will be affected and the cable will be heated. In addition, it is recommended to replace the air switch that is not installed and powered on by stages every five years, because frequent switching and current lead to electric shock aging, resulting in poor contact of the air switch. If the above two items are not strict or the steel ball of the buffer valve is in contact with the inlet with dirt or the gap is too large, take them seriously, and serious cases will lead to electric fire

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