This is the motor control algorithm found in the vast sea of ​​books, the author is a master of motor control, like motor control engineers can be familiar with the mouth, the design efficiency is really high.
Knowing the transformer capacity, find the rated current on each voltage level side 诀a :
The capacity is divided by the voltage value, and the quotient is multiplied by six by ten.
Description: Applicable to any voltage level.
In daily work, some electricians only involve the calculation of the rated current of a transformer of one or two voltage levels. By simplifying the above enthalpy, it is possible to derive the threshold for calculating the rated current of each voltage level side:
The capacity factor is multiplied.
Known transformer capacity, the current value of the first and second protection fuses (commonly known as fuses).
Mouth b:
With a high-voltage fuse-link, the capacity voltage is compared.
Distribution transformer low-voltage fuse-link, the capacity multiplied by 9 divided by 5.
Description:
The correct choice of fuses has a great impact on the safe operation of the transformer. When only fuses are used for high and low voltage side protection of the transformer, the correct selection of the melt is more important. This is a problem that electricians often encounter and have to solve.
The three-phase motor capacity is known, and its rated current is 诀(c): the capacity is divided by the kilovolts, and the quotient coefficient is seven or six.
Description:
(1) The port is suitable for the calculation of the rated current of three-phase motors of any voltage class. It can be explained by formula and port that the rated currents of motors with different voltage levels are different, that is, the voltage is not the same, and the same capacity is removed. The resulting "quotient" is obviously different, and the quotient is different. The number is multiplied by the same coefficient of 0.76, and the resulting current values ​​are also different. If the above port is called a general port, it can be deduced to calculate the rated current for the 220, 380, 660, 3.6kV voltage class motor. When calculating the rated current of a three-phase motor with a dedicated calculation port, the capacity is kW and current amperes. The relationship is directly multiplied, eliminating the capacity divided by kilovolts and the quotient multiplied by a factor of 0.76.
Three-phase two hundred and two motors, 5,000 amps.
Commonly used three hundred and eight motors, one kilowatt two amperes.
Low-voltage six hundred and six motors, kWh two amps.
High-voltage three-kV motor, four kW-ampere.
High voltage six kilovolt motor, eight kilowatts an ampere.
(2) When using port c, the unit of capacity is kW, the unit of voltage is kV, and the unit of current is A. This point must be noted.
(3) The coefficient of 0.76 in the mouth c is a comprehensive value considering the calculation of the motor power factor and efficiency. The power factor is 0.85 and the efficiency is not higher than 0.9. These two values ​​are more suitable for motors with tens of kilowatts or more, and are larger for commonly used motors of 10 kW or less. Therefore, the rated current of the motor calculated by the port c is inaccurate with the value marked on the motor nameplate. This error has little effect on the switch, contactor, and wire of the rated current of the motor below 10 kW.
(4) Using oral calculation skills. When calculating the rated current of a commonly used 380V motor with a port, first use the motor to connect the power supply voltage to 0.38kV to remove 0.76, quotient 2 to multiply the capacity (kW). In the case of a 6kV motor with a large capacity, the capacity kW is exactly a multiple of 6kV, then the capacity is divided by the kilovolts and the quotient is multiplied by the 0.76 factor.
(5) Error. The coefficient of 0.76 in the mouth c is calculated by taking the motor power factor of 0.85 and the efficiency of 0.9, so that there is an error in calculating the rated current of the motor with different power factor and efficiency. The five dedicated ports derived from the port c, the multiples of the capacity (kW) and the current (A), are the quotient of the number of voltage levels (kV) minus 0.76. The special port is easy to calculate, but it should be noted that the error will increase. Generally, the current is larger than the one on the nameplate; the smaller the kilowatt is, the calculated current is slightly smaller than that on the nameplate. In this regard, when calculating the current, when the current reaches more than ten amps or tens of amps, it is not necessary to count after the decimal point. It can be rounded up and rounded up, taking only integers, which is simple and does not affect the practicality. For a smaller current, you only need to count one decimal.
* Measure the current to find the capacity. Measure the no-load current of the nameplate motor and estimate its rated capacity.
The capacity of the unlicensed motor, the measured no-load current value,
Multiply ten by eight to calculate, close to the level of kilowatts.
Note: The mouth is a three-phase asynchronous motor without a nameplate. I don't know what the kilowatt-number of the capacity is. It can be used to estimate the kilowatt-hour of the motor capacity by measuring the no-load current of the motor.
Measure the secondary current of the power transformer and calculate the load capacity of the power transformer.
It is known that the secondary pressure is distributed, and the current is measured in kilowatts.
The voltage level is four hundred volts, one ampere and six kilowatts.
The voltage level is three thousand volts, one ampere of 4.5 kilowatts.
The voltage level is six kilovolts, an integer of nine kilowatts.
The voltage level is ten kilovolts, one to fifteen kilowatts.
The voltage level is 35,000 and 1 amp is 55 kW.
Description:
(1) In the daily work, the electrician often encounters the higher-level department, the management personnel asks about the operation of the power transformer, what is the load? The electrician himself often needs to know what the load of the transformer is. The load current is easy to know. Look directly at the ammeter set on the power distribution unit, or use the corresponding clamp-type ammeter to measure the load power, which cannot be directly seen and detected. This depends on the calculation of the mouth, otherwise it is complicated and time-consuming to calculate with the conventional formula.
(2) "Voltage level is four hundred volts, one ampere is six kilowatts." When the load current of the secondary side (voltage level 400V) of the power transformer is measured, the ampere value is multiplied by a factor of 0.6 to obtain the load power kilowatt.
To measure the current of the incandescent lighting line, calculate the load capacity of the lighting voltage of two hundred and twenty, one ampere two hundred and twenty watts.
Description: The lighting of industrial and mining enterprises uses 220V incandescent lamps. The lighting power supply line refers to the line from the distribution board to each lighting distribution box. The lighting supply main line is generally three-phase four-wire, and single-phase can be used when the load is below 4kW. Lighting distribution lines are lines that are connected from lighting distribution boxes to lighting fixtures such as luminaires or outlets. Regardless of the power supply or distribution line, as long as the current value of a certain phase line is measured with a clamp-type ammeter, and then multiplied by 220 coefficient, the product number is the load capacity of the phase line. Measuring the current capacity, can help the electrician to quickly adjust the three-phase load capacity imbalance of the lighting main line, can help the electrician to analyze the reason why the protective melt is often blown in the distribution box, the cause of the heating of the distribution wire, and so on.
Homemade library ground wave TV double ring indoor antenna: The received ground decimeter wave frequencies are currently in the 500-800 MHZ frequency range. If there is a good field strength in the urban area, low frequency and high frequency should be taken into account. This is the best resonance; The frequency center is around 700MHz, which is converted according to the radio propagation speed and frequency. If the center frequency wavelength is about 42cm, then the diameter of the ring antenna should be 13cm, that is, the diameter should be a quarter of the center frequency wavelength of about 42cm. If we think of a 42cm conductor as a ring with a central frequency and wavelength of 42cm, then its diameter should be close to 13cm. If we make a good antenna, we can get twice the result of receiving ground waves with half the effort!
Indoor Antenna for TV ,Indoor Antenna Walmart,Indoor Antenna Best,Indoor Antenna for Router ,Indoor Antenna for Booster
Yetnorson Antenna Co., Ltd. , https://www.yetnorson.com