How to convert the ratio of the power of the electrical appliance to the cross sectional area of the

Three principles for choosing a wire:

1) Select the cross-section of the wire (safe ampacity) according to the heating conditions for the short distance and small load, and control the current with the heating conditions of the wire, the smaller the cross-sectional area, the better the heat dissipation, and the greater the current passing through the unit area.

2) Long-distance and medium-load on the basis of safe ampacities, according to the voltage loss conditions to select the wire cross-section, long-distance and medium-load is not enough to not heat, but also to consider the voltage loss, to ensure that the voltage to the load point in the qualified range, electrical equipment can work normally.

3) On the basis of the qualified safe current carrying capacity and voltage drop, the large load is selected according to the economic current density, that is, the power loss should also be considered, and the power loss and capital investment should be in the most reasonable range.

What is the safe ampacity of the conductor?

In order to ensure the continuous operation of the wire for a long time, the allowable current density is called the safe ampacity.

The general regulations are: copper wire selection 5 8a mm2; Aluminum wire selection 3 5a mm2.

The safe current carrying capacity should also be determined according to the ultimate temperature, cooling conditions, laying conditions and other comprehensive factors of the core use environment of the wire.

Under normal circumstances, the distance is short, the cross-sectional area is small, the heat dissipation is good, the temperature is low, etc., the conductivity of the wire is stronger, and the upper limit of the safe current carrying capacity is selected;

Long distance, large cross-sectional area, poor heat dissipation, high temperature, poor natural environment, etc., the conductivity of the wire is weaker, and the lower limit of safe current carrying is selected;

For example, the conductivity of bare wires is stronger than insulated wires, overhead wires are stronger than cables, cables buried in the ground are stronger than cables laid on the ground, and so on.

For example, a 15kw three-phase motor selector cable.

The rated current of the three-phase motor is i=p

If it is a close distance (within a few tens of meters), the copper cable is 6 square millimeters, and the aluminum cable is 10 square millimeters.

If it is a medium distance (within a few hundred meters), the copper cable is 10 square millimeters and the aluminum cable is 16 square millimeters.

If it is a long distance (close to kilometers), the copper cable is 16 square millimeters, and the aluminum cable is 25 square millimeters.

The rated current of 90kw i=p ampere.

If it is in close proximity (within a few tens of meters), the copper cable is 50 square millimeters and the aluminum cable is 90 square millimeters.

If it is a long distance (a few hundred meters), the copper cable is 90 square millimeters, and the aluminum cable is 150 square millimeters.

If it is between close distance and long distance, the copper cable is 70 square millimeters and the aluminum cable is 120 square millimeters.

Look at the rated current of the appliance to know how big the wire is.

12,000 kilowatts with how much cable. Three-phase electricity. If it is a dark wire laying, it should be lowered by a grade, such as the dark wire laying of 6 square copper core wires, and the specifications of the power supply line should be determined according to the electrical power of the 4 square copper core wires.

Current i = power p voltage v, the power factor of different inductive loads is different, when calculating household appliances, the power factor cos can be taken. If all appliances plus the total power is 15000 watts, the maximum current is i=p ucos =15000 220*.

Under normal circumstances, it is impossible to use electrical appliances at home at the same time, so add a common factor, and the common coefficient is average. So, the above calculation should be rewritten as i=p*number ucos =15000* that is, the total current value of this family is 42A.

Safe ampacity.

Generally, the safe ampacity of copper conductor is determined according to the allowable maximum temperature of the core, cooling conditions and laying conditions. Generally, the safe current carrying capacity of copper wire is 5 8a mm, and the safe current carrying capacity of aluminum wire is 3 5a mm.

Key points》The safe ampacity of the general copper wire is 5 8a mm, and the safe current carrying capacity of the aluminum wire is 3 5a mm. Such as: the recommended value of the safe ampacities of mm bvv copper wires, and the recommended value of the safe ampacities of 4mm bvv copper wires 4 8A mm = 32A.

The following is the electrical power of the copper core wire of the open wire laying method, if it is a dark wire laying, it should be reduced by a grade, such as 6 square copper core wire dark wire laying, should be determined according to the electrical power of 4 square copper core wire to determine the size of the power cord.

12,000 kilowatts with how much cable. Three-phase electricity.

How many kilowatts can a three-phase four-wire cable 95 square copper wire carry.

The cross-sectional area and power of the wire are compared as follows.

The square plastic copper wire can accommodate 2200W, the square plastic copper wire can accommodate 3500W, the 4 square plastic copper wire can accommodate 5200W, the 6 square plastic copper wire can accommodate 8800W, and the 10 square plastic copper wire can hold 14000W.

Wire load current value:

1 square square, square, 4 square, the wire load current value (partial) specified in the national standard, the allowable long-term load current of the square copper core wire is: 6A---8A

The allowable long-term load current of the square copper core wire is: 8A---15A, the allowable long-term load current of the square copper core wire is: 16A---25A, and the allowable long-term load current of the 4 square copper core wire is:

The allowable long-term load current of 25A---32A, 6 square copper core wire is: 32A---40A.

Wire Square: Know the square of the wire, find the radius of the wire: the number of wires squared (the unit is square millimeters). For example, the square of the wire radius of the square wire is: , and the square gets the millimeter, which is the square wire radius.

The size of the cable is also nominal in terms of squares, and the multi-strand wire is the sum of the cross-sectional area of each Zhouchang wire.

The formula for calculating the cross-sectional area of the cable: the square number of strands of the wire diameter (in millimeters), such as the square of the wire of 48 strands (the diameter of the wire in millimeters per share): square. <>

Three-phase load: p= 3*u*i*cos

p: load power.

u: power supply voltage.

i: Load current.

COS: Power factor (resistive load COS = 1, inductive load COS 1, motor COS

When the power supply and load are constant, calculate the load current i according to the above formula, and then check the "500 volt copper core insulated wire long-term continuous load allowable current carrying capacity meter" in the electrician's manual, and select the appropriate cable diameter according to the line laying form and the working environment temperature of the line, and finally according to: r l s

r: line resistance.

Resistivity of the circuit material (if copper core wire is used, resistivity:

l: the total length of the line.

s: line cross-sectional area.

Calculate the line resistance, and then calculate the voltage drop during the period; Verify that the requirements of the specification are met, and if not, adjust them.

This will allow you to determine the size of the cable.

In this example: 5 horsepower air conditioners with indoor and outdoor fans, the power consumption is about 4kw each, and the total power of 11 units is 44kw

i=p/=√3*u*cosφ=44000/

Then check the "500 volt copper core insulated wire long-term continuous load allowable ampacity meter" in the electrician's manual, and select the appropriate cable diameter according to the line laying form and the working environment temperature of the line

When the form of line laying is open and the working environment temperature is 35 degrees, 16 square millimeters copper core wire (BV, BVV) can be used; If the steel pipe wiring is used, the three-phase four-wire meter needs to use 35 square millimeters of copper core wire. Please pay attention to the laying form when selecting the model.

Finally, according to the total length of the incoming line, the total voltage drop at the end of the incoming line should be calculated to verify whether the skin meets the requirements of the specification.

Summary. 380V, the total power of 36kw should be used how much wire diameter should be used If it is to calculate the current passed by the three-phase motor, calculate the wire diameter. It should be counted as such.

Current = Power Power Factor * Efficiency Current = 36000W Generally, the approximate algorithm is about 1KW rated current of about 2A 1 square copper wire can pass about 5A current. Appear.

380V, the total power of 36kw should be used how much wire diameter should be used If it is to calculate the current passed by the three-phase motor, calculate the wire diameter. This should be counted as a celery. Current = Power Power Factor * Efficiency Electric Head Standby Current = 36000W Generally, the approximate algorithm is 1KW of the slag and the current is about 2A, and 1 square copper wire can pass through the current of about 5A.

Appear. How to judge the quality of a three-phase motor.

The multimeter hits the voltage gear, and the gear is higher than 380V. The red pen voltage bird line jack, the black watch pen common end jack. Measure whether the voltage of the root line of the three Qi Feng is 380V.