Measure energy. §102. Measurement of power and electrical energy. Designation of power of electrical appliances
Power measurement. In chains DC power is measured with an electro- or ferrodynamic wattmeter. Power can also be calculated by multiplying the current and voltage values measured with an ammeter and a voltmeter.
In single-phase current circuits, power measurement can be carried out with an electrodynamic, ferrodynamic or induction wattmeter. Wattmeter 4 (Fig. 336) has two coils: current 2, which is connected to the circuit in series, and voltage 3, which is connected to the circuit in parallel.
The wattmeter is a device that requires correct polarity when turned on, so its generator terminals (the clamps to which the conductors coming from source 1 are connected) are designated with asterisks.
To expand the measurement limits of wattmeters, their current coils are connected to the circuit using shunts or measuring current transformers, and the voltage coils are connected through additional resistors or measuring voltage transformers.
Measurement electrical energy. Measuring method. To account for electrical energy received by consumers or supplied by current sources, electrical energy meters are used. The principle of operation of an electric energy meter is similar to a wattmeter. However, unlike wattmeters, instead of a spiral spring that creates a counteracting torque, meters are equipped with a device similar to an electromagnetic damper that creates a braking force proportional to the rotational speed of the moving system. Therefore, when the device is connected to an electrical circuit, the resulting torque will not cause the moving system to deflect at a certain angle, but rather cause it to rotate at a certain frequency.
The number of revolutions of the moving part of the device will be proportional to the product of power electric current for the time during which it operates, i.e., the amount of electrical energy passing through the device. The number of revolutions of the counter is fixed by a counting mechanism. The gear ratio of this mechanism is chosen so that according to the meter readings it is possible to count not the revolutions, but directly the electrical energy in kilowatt-hours.
The most widespread are ferrodynamic and induction meters; the former are used in DC circuits, the latter - in circuits AC. Electric energy meters include electrical circuits DC and AC current as well as wattmeters.
Ferrodynamic counter(Fig. 337) set on e. p.s. DC. It has two coils: a stationary coil 4 and a moving coil 6. The stationary current coil 4 is divided into two parts, which enclose a ferromagnetic core 5 (usually made of permalloy). The latter allows you to create a strong magnetic field and significant torque in the device, ensuring normal operation of the meter under conditions of shaking and vibration. The use of permalloy helps to reduce the error of the counting mechanism 2 from the hysteresis of the magnetic system (it has a very narrow hysteresis loop).
To reduce the influence of external magnetic fields on meter readings, the magnetic fluxes of individual parts of the current coil have mutually opposite directions (astatic system). In this case, the external field, weakening the flux of one part, accordingly enhances the flux of the other part and generally has a small effect on the resulting torque created by the device. The moving coil 6 of the meter (voltage coil) is located on an armature made in the form of a disk of insulating material or in the form of an aluminum bowl. The coil consists of separate sections connected to collector plates 7 (these connections are not shown in Fig. 337), along which brushes made of thin silver plates slide.
A ferrodynamic meter operates fundamentally like a DC motor, the armature winding of which is connected in parallel, and the field winding is connected in series with the electricity consumer. The armature rotates in the air gap between the poles of the core. The braking torque is created as a result of the interaction of the flux of the permanent magnet 1 with eddy currents arising in the aluminum disk 3 during its rotation.
To compensate for the influence of the friction torque and thereby reduce the instrument error, a compensation coil is installed in ferrodynamic meters or a permalloy petal, which has high magnetic permeability at low field strength, is placed in the magnetic field of a stationary (current) coil. At light loads, this lobe enhances the magnetic flux of the current coil, which leads to an increase in torque and compensation for friction. As the load increases, the induction of the magnetic field of the coil increases, the lobe becomes saturated and its compensating effect ceases to increase.
When the meter operates on e. p.s. strong shocks and impacts are possible, during which the brushes can bounce off the commutator plates. In this case, sparking will occur under the brushes. To prevent it, capacitor C and resistor R1 are connected between the brushes. Temperature error compensation is carried out using the thermistor Rt ( semiconductor device, whose resistance depends on temperature). It is connected together with an additional resistor R2 in parallel with the moving coil. To reduce the effect of shaking and vibration on the operation of the meters, they are installed on e. p.s. on rubber-metal shock absorbers.
Induction counter has two electromagnets (Fig. 338, a), between which an aluminum disk 7 is located. The torque in the device is created as a result of the interaction of alternating magnetic fluxes F1 and F2, created by the coils of electromagnets, with the eddy currents I b1 and I b2 induced by them in the aluminum disk (the same as in a conventional induction measuring mechanism, see § 99).
In an induction meter, the torque M must be proportional to the power P=UIcos?. To do this, coil 6 of one of the electromagnets (current) is connected in series with load 5, and coil 2 of the other (voltage coil) is connected in parallel with the load. In this case, the magnetic flux F1 will be proportional to the current I in the load circuit, and the flux F2 will be proportional to the voltage U applied to the load. To ensure the required phase shift angle? Between the flows Ф1 and Ф2 (so that sin? = cos?) a magnetic shunt 3 is provided in the electromagnet of the voltage coil, through which part of the flow Ф2 is closed
in addition to disk 7. The phase shift angle between flows F1 and F2 is precisely controlled by changing the position of the metal screen 1 located in the path of the flow branching through the magnetic shunt 3.
The braking torque is created in the same way as in a ferrodynamic counter. Compensation for the friction moment is carried out by creating a slight asymmetry in the magnetic circuit of one of the electromagnets using a steel screw.
To prevent rotation of the armature when there is no load under the influence of the force created by the friction-compensating device, a steel brake hook is attached to the meter axis. This hook is attracted to the brake magnet 4, thereby preventing the moving system from rotating without a load.
When the meter is operating under load, the brake hook has virtually no effect on its readings.
In order for the counter disk to rotate in the required direction, it is necessary to follow a certain order of connecting the wires to its terminals. The load terminals of the device, to which the wires coming from the consumer are connected, are designated by the letters I (Fig. 338, b), the generator terminals, to which the wires from the current source or from the alternating current network are connected, are designated by the letters G.
Each person is endowed with his own energy. It can be congenital or acquired during life. There is weak energy, and there is strong energy. According to experts in the field of esotericism, a person’s personal development and success in life depend on it. How to determine your energy field?
There are no specific ways to test a person for his energy power. Energy cannot be measured with instruments. But you can feel it. As a rule, an active, purposeful and productive person has a large supply of vitality. And the one who constantly complains about a lack of energy is a person with low level energy.
Energetically strong man, as a rule, is always in a good mood. He knows how to control his emotions, knows what he is capable of and boldly goes towards his goal. He is not afraid of difficulties, because he feels within himself the strength that will help in difficult times.
People with strong energy are more successful in life. They are cheerful and positive. Their attitude and good health make it easy to achieve their goals. Energetic people can manipulate others, defend their point of view and win attention to their person.
However, those with high energy potential must be able to control their strength. It is better to direct energy for the benefit of yourself and others. If you have strong energy, that is, there is a possibility that you can jinx a person and harm his biofield.
An energetically weak person often gets sick. Even if he has good ideas, he is in no hurry to implement them. People with low energy get tired quickly. They are easily offended or influenced.
Energy levels can be more accurately determined by dreams. What do you dream about most often?
If in a dream you often walk into rivers, forests, or thickets, then this is a sign of an excess of energy. This may also be indicated by music in a dream or a belt that tightly tightens your waist. In this case, everything is fine with energy. True, it happens that excessive energy does not lead to good things. If your forces are directed for good, they will be of real benefit. But if you waste it on trifles, then you will not get anything good from your inner strength.
If you constantly dream of ruins, old houses, abysses, emptiness, hunger, thirst, quarrels, fights, narrow roads and corridors, then you are experiencing a lack of vitality. This is a sign that you urgently need to change your life and restore energy.
Do not rush to despair if you suddenly realize that you are not energetically strong. There is an opinion that human energy is constantly changing. It can be congenital, hereditary (its level depends on many factors, such as place of birth, energy of birth, circumstances of birth, etc.) and acquired.
The acquired energy can change depending on the lifestyle a person leads, what he does, where he lives and with whom he communicates. Based on this, you can easily increase your energy level. There are many ways to do this.
- Firstly, you need to eat well and establish a daily routine.
- Secondly, you need to be alone with yourself and your thoughts more often in order to better understand yourself and your desires.
- Thirdly, you need to give preference to something that brings moral satisfaction.
- Fourthly, you should communicate more with people who set you up for positive emotions.
Knowing your energy potential, you can strengthen it yourself (if it is weak) or direct it in the right direction to achieve your goals. With inner strength, you can achieve anything you want. The main thing is to constantly work on energy, not to let it fail and be able to control it when necessary.
23.10.2013 16:31
Most people's day starts quite early - some get up to study, some to work. Some...
Having been involved in energy practices since 2001, I heard from all sides: “We need to gain energy” or “There is not enough energy.” In qigong they generally said that a person comes with a certain supply of energy received from his parents, and then lives “on it” all his life, or begins to accumulate his own.
At 19 years old, issues of energy accumulation or lack thereof are not as pressing as at 30, and even more so as they are for a woman after the birth of a child.
Brief background: in April 2015 I gave birth to a daughter, in February 2016 I began to revive the site and blog, slowly returning to professional activities within the framework of psychology and wellness and felt that the energy I had was not enough. I didn’t immediately understand what was happening. At first it seemed to me that there was not enough time in the day, then that there was simply not enough time for rest, then that I had accumulated a lack of sleep... As a result, a simple thought-wish came: “If only I had more energy...”
And then my inquisitive mind got hooked: how to measure a person’s energy? Who measures it and with what? How much energy is enough for a day? How much is given at birth? How much is optimal to spend and is it possible to save energy?
Indeed, when we hear: “There is not enough energy,” we certainly understand what we are talking about, but it is not clear how much energy is enough. Let's draw the following parallel: money is often not enough and almost all people want to have more of it. Smart and rich people invest, and they also save money, invest, money works for them, giving them even more money. Is it really possible to do this with energy?
With money, each of us can say exactly or approximately how much he spends on life, how much he can live on, and what his expenses are. Can we say the same about our energy costs? Hardly.
Reflecting on this topic, I came to the conclusion that since I want to keep up with work and things with my daughter during the day, and also undergo one training on financial literacy, then approximately 2.5 times more energy is required than for a normal day earlier. So, one full reserve of strength for a day with my daughter, one reserve for business and 0.5 reserve for training and so that remains on top. In total, I calculated that I need energy per day for 2.5 days. Is it possible to achieve this?
Since I don’t know any units for measuring human energy, although I have been involved in energy practices for many years, I decided to do it simply and accept conventional values. For example, I equated all the energy that is needed for one full (ordinary) day to 1000 units of energy. So now I need 2500 units.
Then the question arose: where did I get these 1000 units? It is clear that you cannot live on reserves forever, and it is unreasonable from an investment point of view. It is necessary to create new assets, that is, to do something that constantly provides energy for basic needs and so that there is something to put off for later. Then how can you get 2500 units per day? Is it possible?
It turned out that it is possible. For example, earlier, by sleeping 8-10 hours, I received about 600-700 units of energy, but now with a small child I can’t sleep for more than 6 hours, and even then it’s sleep with interruptions and wake-ups. Therefore, 6 hours of sleep now gives me only 500 units of energy. Obviously, I can’t get more sleep right now. But I can do other things that will fill me with energy. That is, you need more time to sleep, but I needed investments that would require less time, and the return (energy) would be many times greater.
And I found such ways for myself to increase energy. How did I do this? Very simple. I intuitively and with the help of energy reading determined:
- how much energy do I need;
- what activities and actions can give me energy and how much;
- I chose which actions I will do regularly to gain energy, which ones I will leave as additional options, in reserve.
Calculate how much energy you need for a successful day. Calculate how and where you can get this necessary energy. If you need help in determining the required amount of energy for the day and how to get it for you personally, from March 19 to 23, I invite you to an online consultation via Skype. I will help you calculate your energy consumption for the day, determine how much energy you get from current affairs, how much energy you will have enough to do everything that you plan for yourself, and how you can get this energy.
Live life to the fullest with all the energy you need. Save a little for tomorrow, create an energy cushion for yourself. This is also possible as in finance. This “pillow” will be useful in an emergency situation, for starting new projects, when the business you started has been delayed and requires more effort and time.
Having realized that energy can and should be accumulated, and that more of it can be obtained by simply changing activities, I became calmer, happier, more satisfied with life, because now my strength is clearly calculated. Good luck to you, friends!
Quite often there is a need to measure the power consumed from the network, or generated into the network. This is necessary to account for consumed or generated energy, as well as to ensure normal operation of the power system (avoiding overloads). Power can be measured in several ways - direct and indirect. For direct measurement, a wattmeter is used, and for indirect measurement, an ammeter and voltmeter are used.
DC Power Measurement
Due to the lack of reactive and active components in DC circuits, a wattmeter is very rarely used to measure power. As a rule, the amount of energy consumed or supplied is measured by an indirect method, using the current I in the circuit, and using the voltage U of the load. Then, using the simple formula P=UI, the power value is obtained.
To reduce the influence of internal resistances of devices, devices can be connected using various circuits, namely, with a relatively low load resistance R, the following connection circuit is used:
And for a large value of R, such a scheme:
Power measurement in single-phase AC circuits
The main difference between alternating current circuits and direct current networks, perhaps, is that there are several powers in alternating voltage - . Total is often measured using the same indirect method using an ammeter and voltmeter and its value is equal to S = UI.
Active P=UIcosφ and reactive Q=UIsinφ are measured using a direct method, using a wattmeter. To measure, a wattmeter is connected to the circuit according to the following diagram:
Where the current winding must be connected in series with the load R n, and, accordingly, the voltage winding in parallel with the load.
Reactive power is not measured in single-phase networks. Such experiments are often carried out only in laboratories where wattmeters are switched on according to special circuits.
Power measurement in three-phase AC circuits
As in single-phase networks, also in three-phase networks, the total energy of the network can be measured by an indirect method, that is, using a voltmeter and ammeter according to the diagrams shown above. If the load of the three-phase circuit is symmetrical, then the following formula can be applied:
U l – linear voltage, I – phase current.
If the phase load is not symmetrical, then the power of each phase is summed up:
When measuring active energy in a four-wire circuit using three wattmeters, as shown below:
The total energy consumed from the network will be the sum of the wattmeter readings:
The method of measuring with two wattmeters has also become equally widespread (applicable only for three-wire circuits):
The sum of their readings can be expressed by the following expression:
For a symmetrical load, the same formula applies as for total energy:
Where φ is the shift between current and voltage (phase shift angle).
The reactive component is measured according to the same scheme (see figure c)) and in this case it will be equal to the algebraic difference between the instrument indicators:
If the network is not symmetrical, then to measure the reactive component, two or three wattmeters are used, which are connected according to different circuits.
The process of measuring active and reactive power
The active power of the alternating voltage circuit is measured. They are connected using the same circuits as wattmeters. Reactive energy in single-phase consumers is not metered in our country. It is metered in three-phase circuits of large industrial enterprises that consume large volumes of electricity. Active energy meters are marked SA, reactive SR. Electronic electricity meters are also widely used.
The energy of a substance is its ability to do work. There are many types of energy. Chemists are most “interested” in kinetic and potential energy.
1. Kinetic energy
Kinetic energy is the energy of movement.
Any moving body has kinetic energy. The greater the mass of a body and its speed, the more kinetic energy it has. When in contact with another body, part of the kinetic energy is transferred to this body. For example, when we hit a ball with a billiard cue, we transfer some part of the kinetic energy to it (the ball) - the ball begins to move. When it collides with another ball, part of the energy is again transferred (redistributed) and two balls will already be in motion. Kinetic energy can be converted into another type of energy. Thus, at a hydroelectric power station, the kinetic energy of falling water is converted into electrical energy generated by a generator turbine.
Remember the law of conservation of energy? - “Energy does not disappear anywhere without a trace and does not appear out of nowhere - it only passes from one form to another” (here a reservation should be made that this does not apply to nuclear reactions).
2. Potential energy
Potential energy is "hidden" energy, which depends on the position of bodies and can manifest itself under certain conditions.
So, an icicle hanging from the roof of a house does not have kinetic energy (since it does not move), but it does have “good” potential energy (which is greater, the more massive the icicle and the higher the roof of the house). Under certain conditions (when the sun warms up well), the icicle can break off and fall to the ground. In this case, the potential energy contained in it will turn into kinetic energy.
However, chemists are not interested in such aspects of potential energy. They are interested in the potential energy inherent in chemical bonds:
- How is the energy of the food we eat stored in the body?
- Why doesn’t a car run without gasoline?...
3. How to measure energy
It is not difficult for physicists to measure the potential and kinetic energies of a body. To do this, you need to know the mass of the body, its speed (kinetic energy) or distance to the ground (potential energy).
For chemists, the task becomes more complicated.
The potential energy stored in chemical bonds depends on the type and number of bonds that can be broken.
To measure the kinetic energy of a substance, it is enough to measure its temperature. In this case, the average kinetic energy of particles moving in the substance is measured.
A measure of the total amount of energy of any substance is its heat. For example, the temperature of the water in your glass and in the Black Sea may be the same. But to increase it, say, by 1°C, a completely different amount of energy is needed for a glass and for the sea. Thus, we can say that heat takes into account such a component of a substance as volume.
The SI unit of heat is the Joule. However, another metric system is also in use - calorie (cal):
1 cal = 4.184 J
A calorie is a fairly small unit of measurement:
Therefore, kilocalorie (kcal) is more often used: 1 kcal = 1000 cal.