Electric motors began to be made many years ago, but they aroused the greatest interest when they began to replace engines running on gasoline. The efficiency of an electric motor is one of the most important indicators of a motor. It shows the productivity of the system as a whole, characterizing how well the mechanism converts energy. The performance level is measured in percent or graded on a scale from 0 to 1.
Content
- A bit of history and modernity
- The main characteristics of the operation of motors
- What are the advantages of an electric motor
- Loss of energy when the engine heats up
- Reasons for the drop in efficiency
- Elements affecting power
- Functionality limit
- Is there ever a value above 100%
- Hydroelectric power plant - a prototype of a perpetual mechanism
- Permanent magnets - electricity producers
A bit of history and modernity
The main impetus for the development of electric motors was the discovery of the law of electromagnetic induction. It says that induction current moves in such a way as to oppose what caused it. On this basis, the first electric motor appeared.
Today's production of electric motors follows the same theory, but the current models have many differences from the original. The power of electric motors has increased, they have become smaller, and, importantly, the efficiency has increased. If we compare it with the efficiency of an internal combustion engine, then the result will not be in favor of the latter. The greatest efficiency of such a motor is no more than 45%.
The main characteristics of the operation of motors
The main function of the engine is conversion of electrical energy into mechanical. Efficiency is an indicator of the productivity of a given function. The formula for the efficiency of an electric motor is built as follows:
n = p2 / p1,
where p1 is the supplied electrical power and p2 is the net mechanical power generated by the electric motor.
However, not all so simple. The functions of the engine and the area of its use, many other variables will refine the calculation and make it more individual.
What are the advantages of an electric motor
There are many advantages to electric motors over internal combustion engines. Here is some of them:
-
High efficiency. - The internal combustion engine spends about half of the energy on heating the motor. In the case of an electric motor, very little energy is expended on this.
- The electric motor is much lighter and more compact. The new Yasa Motors engine weighs only twenty-five kg and is powerful enough.
- Long service life.
- Electric cars do not need a gearbox.
- Environmentally friendly: the machine does not emit harmful emissions into the atmosphere. However, this is only partly true, because power plants use natural resources to obtain energy - gas, coal, nuclear reactions, and this is a harmful factor.
Loss of energy when the engine heats up
Energy losses during engine heating play an important role in the operation of the electric motor. Most often, the drop in efficiency occurs due to natural heat transfer during the operation of the mechanism.
An electric motor usually heats up from friction, and also because of the electrical and magnetic forces acting on it during operation. For example, the power consumption of the motor was 100 rubles, and the mechanical energy was estimated at 80 rubles. In this case, the efficiency of the electric motor will be 80%.
To cool the electric motor, there are special fans that drive air through a running motor and thereby create a more optimal temperature for its operation.
The degree of load has a huge impact on the performance of the electric motor. Without load, the motor runs at 0% efficiency. If the engine is loaded by 25%, then the efficiency will be equal to 83%. In the mode of one hundred percent load, the efficiency will be 87%.
Reasons for the drop in efficiency
There are many indicators that reduce the efficiency of an electric motor. Fortunately, there are ways to determine exactly what caused a drop in efficiency. For example, you can track the presence of a gap, which partially transfers power from the mains to the stator, and then transfers it to the rotor. There may also be energy losses in the starter.
There is also energy leakage due to eddy currents and magnetization reversal of the stator cores. Losses due to teeth in the rotor and stator also occur in an induction motor. Eddy currents can appear in some parts of the motor. For such reasons, efficiency can drop by half a percent. Asynchronous motors are built with these features in mind, and the efficiency in such motors ranges from 80 to 90 percent.
Elements affecting power
Electric motors have some drawbacks that affect performance in an unsatisfactory manner. Particularly unpleasant moments include:
- weak electric trigger,
- strong level of starting current;
- inconsistency of the machine shaft with the load.
The above leads to the fact that the useful effect of the device decreases. To increase efficiency, they strive to provide the engine load up to 75 percent and increase the power proportions. There are also special devices for regulating the ranges of the supplied current and its power, which also leads to an increase in efficiency and efficiency.
One of the most well-known devices for increasing the recoil of an electric motor is considered to be a soft start mechanism, which limits the rate of growth of the starting current. You can also use frequency converters to change the speed of rotation of the motor by changing the frequency of the voltage. The above leads to a decrease in energy consumption and provides a soft start of the engine, high balancing accuracy. In addition, the starting torque increases, and when the load is unstable, the speed of movement is stabilized. As a result, the performance of the engine increases.
Functionality limit
Based on the type of design, the PD coefficient in electric motors can range from 10 to 99 percent. It all depends on the specific type of engine. For example, the efficiency of a piston-type pump engine reaches 70-90%. The final effect depends on the manufacturer, device structure, etc.
The same applies to the efficiency of the crane motor. When this value rises to 90%, it means that 90% of the consumed electricity is spent on performing machine work, and the remaining percentage is spent on heating the parts. Nevertheless, there are especially successful engine models, the PD coefficient of which reaches almost 100%, but is not equal to the specified value.
Is there ever a value above 100%
Everyone knows that electric motors, the efficiency of which exceeds 100%, are impossible according to the laws of nature, since this contradicts the main law of conservation of energy. Everything is explained by the fact that energy does not come from nowhere and does not disappear anywhere. Therefore, every engine has a need for an energy source. They can be:
- fuel;
- electricity;
- sunlight etc.
But at the same time, none of the listed sources is eternal, moreover, the reserves of each must be accumulated. However, if there was a source of energy that needs to be collected and accumulated, then it would be quite possible to create an engine, the useful effect of which would be more than 100%.
Hydroelectric power plant - a prototype of a perpetual mechanism
If we consider the principle of operation of a hydroelectric power station, we can see that electricity is generated in it at the expense of waterthat falls from a great height. Electricity is generated by a turbine driven by falling water. Water rushes downward due to gravity.
It acts constantly, without weakening or disappearing. After the water has used up some energy, it turns into steam and naturally returns to the reservoir. This can be repeated many times. As a result, electrical energy is generated without loss of resources.
The sun heats the earth by participating in the evaporation of water, gravity does double work, participating in the fall water, as well as in the production of precipitation - after all, it is due to the attraction of the earth that water from clouds tends to fall way down. In general, it turns out that a hydroelectric power plant is a mechanism that converts the energy of falling water into electrical energy with an efficiency of more than one hundred percent.
From this it is clear that the search for an engine with an efficiency of more than 100% is not groundless, because there are other resources, besides gravity, that cannot be exhausted.
Permanent magnets - electricity producers
A permanent magnet can also be an interesting object for obtaining energy, because it does not come to it from the outside, and the magnetic field remains unchanged even after the work has already been completed.
The magnet tends to attract various things made of iron and its alloys. Having attracted a certain object to him, he does not expend his energy, it is just a property that he possesses and which he cannot exhaust. Therefore, on the basis of magnets, it would be possible to make an engine close to perpetual. Of course, one cannot but take into account the wear and tear of parts, but the very principle of operation of a magnet creates conditions for constant work without wasting money.
True, some scientists believe that over time, the magnet loses its properties. This is unverified information, but this turn of events cannot be ignored either.
On the basis of magnets, they have tried many times to create a semblance of a perpetual motion machine, but so far these attempts have not led to anything. Of course, I want to believe that in the foreseeable future, scientists will make a breakthrough and invent an engine that will run on renewable energy.
Interestingly, one of the domestic inventors, V. Chernyshov - recently demonstrated a description of a motor based on a static magnet, and its efficiency, as the experimenter himself attests, is more than 100%.
The coefficient of PD of an electric motor is an extremely important indicator that determines the performance of an engine. The higher its score, the more efficient the engine is. In a motor with an efficiency of 95%, almost all of the power expended is spent on performing work and only 5% is spent on unnecessary action (for example, heating parts). Today's diesel engines are capable of achieving an efficiency value of 45%. The coefficient is small, but nevertheless it is considered one of the most productive. The efficiency of gasoline-fueled carburetor engines is even lower.
