Rated power, active power, reactive power, apparent power, power factor and crest factor - Database & Sql Blog Articles

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The difference and connection between active power and rated power of three-phase asynchronous motor:
The rated power is the mechanical power at which the motor operates at the rated point.
Rated power = sqrt (3) * rated voltage * rated current * power factor * efficiency. This is specifically referred to as the rated point.

Apparent power = sqrt(3) * voltage * current.
Active power = sqrt (3) * voltage * current * power factor, this active power is the electrical power input by the motor, it is different from the apparent power is the intersection of the AC voltage and current, or the energy storage component inductance in the motor Caused.

Efficiency is a completely different concept of stator-rotor copper loss, iron loss and mechanical loss in the motor. Reactive power has no power loss, only energy is stored in the energy storage element in the form of a magnetic field, and is not transmitted to the mechanical power output, and the loss of efficiency is all converted into thermal energy, which causes the motor to rise in temperature.
The electric motor absorbs electric energy from the power grid and passes the regulation of the electromagnetic induction law, which turns the rotor of the electric motor to rotate, and drives the load machinery to do work, thus converting the electric energy into mechanical energy.
The energy output by the motor is the rated power of the motor.
When the motor is running, many losses such as coil heating and bearing friction are lost to the motor.
Adding the rated power and all the losses is the active power that the motor absorbs from the grid.
The electric motor converts electrical energy into mechanical energy, which is inseparable from the magnetic field. The establishment of the magnetic field is formed by the energization of the motor coil. The formation of the magnetic field also requires energy. This part of the energy is not converted into mechanical energy and thermal energy, which is equivalent to the medium. Is the reactive power of the motor.
Active power + reactive power = apparent power, note: This is vector plus å“Ÿ.
Efficiency = rated power ÷ active power × 100% is always less than 1

First, the concept of active power, reactive power, apparent power, power factor and peak factor 1. Active power: energy that can be converted into other forms of energy (heat, light, kinetic energy). Expressed in P, the unit is W. In general, active power is relative to purely resistive loads. 2. Reactive power: The power that is transmitted from the energy source to the load and reflects the power exchange condition is the reactive power. Expressed in Q, the unit is Var. It is generated by inductive loads, capacitive loads, and distortion of voltage and current. This power can cause additional current losses. 3. Apparent power: The sum of the geometry of active and reactive power (ie, the root mean square of the sum of squares), which is used to represent the capacity of an electrical device. Expressed in S, the unit is VA. 4. Power factor: The phase difference between the sinusoidal AC voltage and the current is called the power factor angle, expressed in Φ, there is no unit, and the cosine of this power factor angle is called the power factor. It depends on the circuit component parameters and operating frequency. The pure resistor circuit has a power factor of 1, and the pure inductor-capacitor circuit has a power factor of zero. Power factor cosineΦ=P/S. 5. Crest factor: As shown on the right, the blue sine wave is the voltage waveform and the red is the current waveform. The crest factor is the ratio of the peak value of the instantaneous value of the current to its effective value. It is used to describe the inrush current. If the crest factor of the power supply equipment is higher, it indicates that the equipment is more resistant to impact.

Active power: In an AC circuit, the power supply emits an average value of instantaneous power (or the power consumed by the load resistor) in one cycle. It is called "active power". Reactive power: in a circuit with inductance or capacitance. In every half cycle, the energy of the power source is converted into a magnetic field (or electric field) energy. Then, it is released. The stored magnetic field (or electric field) energy is returned to the power source. Only this energy exchange is performed. Really consume energy. We call this exchanged power value "reactive power". Apparent power: in the AC circuit with impedance. The product of the voltage rms value and the current rms value. It is called "apparent power". It is not the average of the actual work done. It is not the maximum rate of exchange energy. It is simply a simple method of designing the motor or electrical equipment. Relationship: square of apparent power = square of active power + square of reactive power The power S=UI or S=P/COS∮ and the capacity of the transformer is also S=UI. Therefore, the rated capacity of the transformer is equal to the rated apparent power. Or both are equivalent. If the rated capacity is 100kVA, then the rated Apparent power is also 1 000kVA

1. Active power: The electric power required to maintain the normal operation of electrical equipment, that is, the electrical power required to directly convert electrical energy into other forms of energy. The active power in AC is expressed as: P = UIcos φ P represents the active power unit: watt (W) kW ( KW ) MW ( MW ) U represents the voltage I represents the current Cos φ represents the power factor 2, reactive power: used for the internal electric field of the circuit Exchange with magnetic fields and used to establish the electrical power required to maintain the magnetic field. It does not work externally, it only performs energy conversion inside the circuit. (Active power does work, reactive power does not work) Reactive power uses Q. Unit: Sow (Var) KVar (KVar) Where there are electromagnetic coils, electrical equipment that needs to establish and maintain a magnetic field must have reactive power. For example: a 40-watt fluorescent lamp that requires 40 watts of active power and 80 var (var) reactive power to establish and maintain an electromagnetic sound field. 3. Apparent power: the total power on the circuit. Expressed in S, unit: volt-ampere (VA) kVA, which is the product of voltage and current in AC: S=UI4, power factor: cosφ is a factor that measures the efficiency of electrical equipment. 0 ≤ cosφ ≤ 1 . Is a ratio of active power to apparent power. Cos φ = P/S . φ represents the phase difference (phase angle) between voltage and current. The magnitude of the cos φ value is related to the load characteristics of the electrical equipment. (1) Pure electrical resistance equipment, because it directly consumes power to convert electrical energy into thermal energy, there is no phase difference, φ =0 cos φ =1 so P=S resistive electrical appliances only consume active power. (2) Inductive electrical appliances (electrical devices with inductive coils) phase difference (phase angle) 0 °<φ< 90 ° Capacitive electrical appliances (electrical appliances with capacitance) -90 °≤φ≤ 0 ° apparent power, active power, none The relationship between power and power factor (as shown in Figure 1): S 2 =Q 2 +P 2Cos φ =P/S Conclusion: Increasing the power factor reduces the output of reactive power on the line and reduces The apparent power saves energy and reduces apparent power and current. 5. Principle of reactive power compensation The harm of excessive reactive power: (1) Reduce the output of active power of power generation equipment. (2) Reduce the power supply capacity of wire equipment. (3) causing an increase in voltage loss on the line and an increase in power loss. (4) The electrical equipment is inefficient at low power operation, and the voltage is reduced or even not working properly. The artificial method is used to set the reactive power compensation device to ensure the reactive power required by the electrical equipment and reduce the reactive power provided on the line. Reactive power compensation is a method in which a capacitive power device and an inductive power load are connected in parallel on the same line. 6. Reactive power compensation: (1) Centralized compensation: a method of concentrating capacitive power load devices to compensate all electrical equipment . (2) Local compensation: For a single electrical equipment, our power saver uses the principle of reactive power compensation to perform reactive power compensation on a single or partial power equipment, improve the power factor of the power equipment, and reduce the reactive power provided by the line. The power, thereby reducing the apparent power and current caused by the reactive power to form active loss, achieves the purpose of saving electricity.