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Can We Benefit From Reactive Power of Diesel Generator

Sep. 20, 2019

As we know, there are three kinds of power in power system of diesel generator: active power, reactive power, apparent power, they have some certain relationships. Active power is used for acting. Active power can be transformed into mechanical energy, thermal energy, light energy and other energy forms that we need.


But what role does reactive power play in energy conversion? Even if we consume reactive power, the power supply company does not charge us for it. And the important point is that the existence of reactive power requires the design of the transformers need to increase the capacity, increase the cross-section area of conductors, so that we spend a lot of money. It seem that reactive power has little benefit to us, all harm. So whether reactive power is really useless? Today Starlight Power answers for you.


Volvo generator

Firstly, we learn what is reactive power in diesel genset.

Reactive power is more abstract. It is used for electric field and magnetic field in the circuit, and to establish and maintain the electric power of magnetic field in electrical equipment. For electrical equipment with electromagnetic coils, reactive power must be consumed in order to establish magnetic field. Inductive or capacitive components are consumers and providers of reactive power.


Secondly, usually somebody think of reactive power, maybe think it is useless, of course, there also are some harms in reactive power.


1.Reduce the output of generator active power, the reason is that the total capacity of the generator (the apparent power) is constant. If the reactive power is too much, the active power will be reduced accordingly, otherwise the generator will overload.

2.Reducing the power supply capacity of transmission and substation equipment, same as diesel power generator.

3.Causing the line voltage loss to increase, the reactive current component in the circuit increases, and the total current increases. Voltage drop: δU=IZ, voltage drop is proportional to current, and the line voltage drop increases. It is necessary to increase the section of the line accordingly, resulting in an increase in investment.


Then, here is some harms from reactive power. Whatever it is, there will always be bad and good. So, we still can benefit from reactive power of diesel generator.


1.Many electrical equipment work according to the principle of electromagnetic induction, such as distribution transformer, motor, etc. The motor needs to establish and maintain a rotating magnetic field to make the rotor rotate, thus driving the mechanical movement. The rotor magnetic field of the motor is established by obtaining reactive power from the power supply.

2.Transformers also need reactive power in order to make the primary coil of the transformer produce magnetic field and induce voltage in the secondary coil.


Therefore, without reactive power, the motor will not rotate, the transformer will not change voltage, and the AC contactor will not suck in. It can be seen that reactive power plays an auxiliary role in the process of energy conversion and voltage transformation. Without reactive power, it is impossible to establish magnetic field and convert electrical energy into mechanical energy.


Rotor and motor is one of spare parts in diesel generator set, so reactive power is an important role for diesel genset.


Finally, we already are benefited from reactive power. Without reactive power there would be no active power in most of our well known electrical machines.


Reactive power actually paves the way for the active power to be delivered. Reactive power is responsible to establish the magnetic flux in AC generators (aka alternators) which in turn, sets the output voltage to the desired level.


Induction motors transfer active power to the rotor by means of the reactive power “consumed” (exchanged between the stator and the mains) by the stator. The reactive power establishes the rotating magnetic field who drags the rotor, hence transforming the active power into rotary mechanical power.


Antennae, induction ovens, motors, transformers, microwave ovens, cellphones, radios, TV’s and all sort of communication apparatuses makes use of reactive power to pave the way to deliver active power, in terms of mechanical power, electrical power, heat, information etc.


Likewise, capacitors can exchange reactive power by establishing an electrical field. Capacitors and inductors have very important rules in electrical and electronics circuitry.


In general, you can think about reactive power in analogy to the seats in an aircraft. Seats don’t make money for the airline, but passengers do. Passengers are the active power to be transported, but they require seats to be seated.


The aircraft can fly empty, at its lowest efficiency factor, but it can also fly full, at its highest efficiency factor. It’s just an arithmetical percentage calculation.


Likewise, with a fundamental mathematical difference, electrical circuits can operate at a desired power factor, which is a vectorial relation between active and reactive power. 

We should remember that reactive power is not useless power, reactive power is beneficial and harmful. When we design it, we try to eliminate its harmfulness. This involves the problem of reactive power compensation. Hope next time, we can share how to do reactive power compensation.

Starlight Power is a very professional supplier and manufacturer of diesel generator, whatever in technical support or after-sales, they are very professional. More importantly, in terms of product quality, they are also very popular in overseas markets. If possible, welcome to contact us, we believe you will satisfied. 

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