What is the apparent power, active power and reactive power of the three-phase asynchronous motor, the big blue motor to reveal the secret!


In an AC circuit, there are two types of electric power supplied by a power source; one is active power and the other is reactive power.

Active power is the electrical power required to keep a consumer operating normally, that is, the electrical power that converts electrical energy into other forms of energy (mechanical, optical, thermal). For example, a 5.5 kW electric motor converts 5.5 kW of electrical energy into mechanical energy, which drives pump water pumping or thresher threshing; various lighting devices convert electrical energy into light energy for people to live and work with. The sign of active power is denoted by P and is expressed in watts (W), kilowatts (kW), megawatts (MW).

Reactive power is relatively abstract, it is used to exchange electric and magnetic fields in the circuit, and is used to establish and maintain the electrical power of the magnetic field in electrical equipment. It does not work externally, but instead transforms it into other forms of energy. For electrical equipment with electromagnetic coils, reactive power must be consumed to establish a magnetic field. Reactive power has no power loss, but 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. For example, a 40-watt fluorescent lamp requires more than 40 watts of active power (the ballast also consumes a part of the active power) to emit light. It also needs about 80 consuming reactive power for the ballast coil to establish an alternating magnetic field. Because it does not work externally, it is called "reactive." The sign of reactive power is represented by Q, and the unit is either Var or kVar.

Apparent power refers to the total power emitted by the generator, which can be divided into active part and reactive part. The active part is the power that is lost by the heating of the wire or the purely resistive load. This part of the power is called active power because of the work done. The reactive power is the power lost on the non-pure resistive load. It can be considered as the loss of the phase difference between voltage and current. Reactive power does not work, but to ensure that the transmission of active power must first meet the reactive power of the grid.

The following Dalan motor small series gives you a clear explanation:

The relationship between apparent power, active power and rated power of a 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 being the intersection of the AC voltage and current, or the inductance of the energy storage component in the motor.

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.

Motor rated power + motor loss = active power absorbed by the motor 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 哟. Efficiency = rated power ÷ active power × 100% is always less than 1.




----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant

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