What is the main difference between electrical and electronics?

We know that the term electronics has its origin from the invention of the diode and triode valves from electricity. Therefore we can define electronics in terms of electronics as a branch of electrical that studies about an active electrical device with a passive device which is known as electronics.

Some used to say - the study of high voltage AC and AC devices is called electrical while the study of low voltage DC and DC devices is called electronics.

This is partly true, but not absolute because in power electronics we control high voltage AC power using active electronic devices such as SCR, Triac, etc., so the branch is called power electronics and not electrical.

If you glow an ordinary 3v filament bulb, it is not part of the electronics, while it is part of the electromagnet, using battery DC.

Electrical also studies the magnetic and heating effects of electricity. Electronics may also include magnetic and thermal measurements but active devices must include this.

Controlling the light intensity of the 3v filament bulb using a rheostat comes in electrons while controlling the light intensity of the 3v filament bulb using transistors and presets comes into the electronics.

Some people used to say - electrical equipment manages the flow of electricity and electronic example manages the flow of information. This is true whether they work with AC or DC.

For example, we can say that a DC supply, such as a cell, is an electrical device because it is designed to manage the flow of power. Remember that television is an electronic device because its electronic circuits manage the flow of information in the form of sounds and pictures.

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Can low voltage level damage home appliances?

The risk of loss is high.

To understand the explanation better you need to know the following:

Ohm's law: At constant temperature and resistance, the voltage is directly proportional to the current. That is, as the voltage falls, the current decreases.

• P = V * I: is equal to the current of the power voltage. Where V = rated voltage and I = current drawn by the instrument.
• Many practical loads use different combinations of resistors, capacitors, and inductors.
• Each device has its own voltage rating and current (or power rating). When a low voltage is applied to one device, the device will operate on other operating parameters (ie, current and power will change).
• When a low voltage is applied to an appliance, the device will draw more current to meet the rated power (P = V * I). That is, there will be more current through the conductor. The current carrying capacity of the conductor in the equipment will determine the cause of the damage.

When the current drawn by the conductor exceeds the current carrying capacity of the conductor, it generates more heat which can cause wire, insulation failure to burn and equipment will be damaged.

If the current passing through the conductor is capable of carrying it, the device will not suffer damage. - This explanation is for inductive loads like a motor.

For resistive loads, lower voltage means less power. When a low voltage is applied to an incandescent bulb. It will glow with low wattage (ie the bulb does not give the final brightness).

What is the difference between a series circuit and a parallel circuit?

series circuit:-

In a series circuit,

• There is only one current route,
• All components have the same current through them.
• The sum of potential drops in each component is equal to the EMF of the source. This statement is known as Kirchoff's voltage law.

In a series circuit, it follows that if there is a break in any part of the circuit, no current flows. This is why fuses, circuit breakers, and safety switches are kept in series with the equipment they are designed to protect.

The ammeter is placed in series with the component whose current you are trying to measure.

The properties of a series circuit are:

• Resistance is additive.
• The current remains the same throughout the circuit.
• The voltage is additive.
• Power is additive.

parallel circuit:-

In the parallel circuit,

• There is more than one current route,
• All components have the same capacity.
• The sum of the current flowing at any point is equal to the sum of the currents flowing from that point. This statement is known as Kirchoff's current rule.

In parallel circuits, each component acts as if it were the only one present. One break in one circuit does not affect the others. Unlike a series circuit, this series is not all out!

The voltmeter is placed parallel to the component whose voltage you are trying to measure.

The properties of a parallel circuit are:

• The total resistance is less than anyone resistance.
• The voltage through the circuit remains the same.
• The present is summative.
• Power is additive.

What is a capacitor bank and why is it used?

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Capacitors (or capacitor banks) are used to improve the operational efficiency of electric power systems and to help transmission and distribution system voltage stability during disturbances and high load conditions.

• Capacitors are used to cancel the current effects of motors and transformers.
• The capacitor can reduce system losses and provide voltage support.
• Another advantage of capacitors is that they can reduce the total current flowing through a wire and thus leave capacitance in conductors for additional loads.
• Capacitor banks can be continuously left online to meet the steady-state reactive power requirements of the system or they can be switched on or off to meet the dynamic reactive requirements.

There are two types of reactive power compensation in a power system - series and shunt.

In distribution compensation, shunt compensation can be installed near the load, along with distribution feeders or in transmission substations. 

Each application has a different purpose.

• Shunt reactive compensation can be inductive or capacitive.
• At the load level, at distribution substations and with distribution feeders, compensation is usually capacitive.
• In a transmission substation, both inductive snd capacitive reactive compensation is used.
• Capacitor banks are installed on the distribution line to reduce losses, improve voltage support and provide additional load capacity on the distribution system. Reducing the loss of distribution system with capacitors is very effective as it also reduces the loss of transmission.

The closer a capacitor is installed to the actual inductive load itself, the more advantageous it is. For example, if capacitors are properly installed at motor terminals in industrial loads, the losses in the lines feeding the motor are minimized, the distribution losses will be minimized, the transmission losses will be minimized and the generation losses Will also be reduced.

Why do birds get seated on electrical lines?

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The prerequisites for electric current are:

• Completeness of the circuit - The flow of electricity can be considered as a process in which electrons are drawn from the earth by a power plant. These electrons travel through electrical lines to our devices and travel all the way back to Earth. This circuit has to be completed for the current flow.
• Another possible factor determining the direction of flow of current is the (electric) potential. Current always flows from high potential to low capacitance. In other words, it can be said that electrons flow from lower potentials to higher ones. (The direction of electric current is opposite to that of electrons). Therefore we need a potential difference in current for the flow.
• The path of least resistance - In the case of a parallel path, the factor that flows the current into the current is presented by the (electrical) resistance path. The current will always flow in the path that provides the least resistance.
• Now consider that a bird is sitting on the living wire and is not touching any other wire:
• The first circuit is incomplete because the bird is not in contact with any other wire.
• There is no possible difference because both legs of the bird are touching the same wire at the same constant potential
• The resistance presented by the bird is also much higher than that presented by the copper/aluminium wire which are known to be good conductors of electricity hence there is an almost negligible amount of current flow through the bird which does not harm the bird.
• Indeed, when birds stand on a single-phase power line with both feet, they get electric shock in the nano volt range, making them feel nothing. Even though they do not complete a path on the ground, they are actually in parallel circuits with the power line.
• Since the electric line does not have 0 ohms of resistance, even between the legs of the bird, some electric current deviates into the bird. That is Ohm's law. Electricity will always follow all the given paths, but how much current flows through those paths depends on their resistance.
• If the bird touches the ground while sitting on the wire or flaps its wings and touches another electric wire with a different voltage, it will be shocked and likely to die from electrocution. This is because its body becomes a path for electricity to reach either a ground (any voltage) or a location with a different voltage (another wire at a different voltage).

What is Auto Transformer? Its advantages, disadvantages and applications.

We know that in ordinary transformers primary and secondary windings are magnetically connected while in autotransformers a winding is used which is tapped from the centre and electrically connected. An ordinary transformer has no magnetic coupling and mutually induced current and the autotransformer has a self. Inspired EMF. We can use this transformer step as well as captain, but generally, we use this transformer below.

V1 = primary applied voltage

V2 = secondary voltage across the load

i1 = primary current

i2 = nordcurrent

N1 = number pattern between a and b

N2 = the number of trains between C and B.

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In the diagram terminal, a and b are called primary windings and terminals c and b are called secondary windings. The secondary winding has less number of tan as compared to primary winding as we are using this transformer as a step-down transformer. Current flow in the primary winding is I1 and current flow in the secondary winding is I2

The number between A and c is N1 – N2. And the secondary winding has the number of turns and N2-N1. And the law is connected between C and B which is the secondary winding. And terminal c can be called a rotary switch. With the rotary switch, we can adjust the voltage. Here is the picture of the rotary switch.

It is a 1 kVA autotransformer that supplies single phase 50 Hz. And there is the rotary switch which you can see in the picture black knob associated with terminal C in the internal circuit.

Always remember -

• If the number of turns in the primary is more than the secondary, it is called step down transformer.

• And if the number of windings in the secondary winding exceeds the primary winding, it is called a step-up transformer.

Change ratio

K = V2 / V1 = E2 / E1 = i1 / i2

K <1 always

Benefit

The autotransformer has only one winding so the copper consumption is less.

Less expensive.

Less loss than two winding transformers.

Low leakage flow.

loss

The main disadvantage of autotransformer by secondary winding is not insulated from primary winding if we use the transformer as a step-down transformer and if the secondary winding is broken then all the full load primary voltages fall into the secondary winding which is hazardous to the operator. As well as devices. Your equipment will be damaged.

Applications

Used as a voltage regulator.

Use the stator of the square full cage induction motor as a starter to deliver 50 to 60% of the absolute full voltage.

Used in power transmission and distribution.

How did electricity and thunders happen?

When I was younger I always wondered how this lightning and thunder is and I know you were thinking about this too so today we will discuss about how lightning and thunder came. Let's get started

Lightning is the most spectacular element of a thunderstorm. This is actually how thunder got his name. Wait a minute, how is Vajra related to electricity? Well, lightning causes thunder.

Lightning is the discharge of electricity. A single stroke of lightning can heat up to 30,000 ° C (54,000 ° F) in the air around it! This excessive heating causes the air to actively expand rapidly. The expansion creates a health wave that turns into a sharp sound wave, known as a rumble.

Because the adversaries draw, the negative charging at the bottom of the storm wants to list the ground with a positive charge. Once the negative charge at the bottom of the cloud becomes large enough, the flow of the negative charge is called a steady leader that moves towards the Earth. Positive charges on the ground attract the leader, so the positive charge flows upwards from the ground. When the phased leader and positive charge meet, a strong electric current charges positively into the cloud. This electric current is known as the changing stroke. We see this as a bright flash of an electric bolt.

And another question I also think that when we hear thunder and thunder, we saw earlier that we hear the sound of thunder so how did it happen?

The speed of light is greater than the sound of light, so we see lightning before and after it.

And one more thing when this lightning strikes thousands of Imams of flow through your body. And this will stop your heartbeat. So when there is lightning and disturbances, do not stay outside the house and protect your family as well.

And when this power removes your TV plug, refrigerator plug and turns off your mobile charger plug. This lightning can damage your gyrates.

Another question arises that when lightning flashes and thunder then why do we hear the sound?

Thunder is caused by the rapid expansion of air around the path of a lightning bolt. ... However, the thunder and scurrilous sounds we hear actually come from the rapid expansion of the air around the light bolt.

The thrust of the thunder can be expressed in decibels (dB). A clap of thunder usually registers at about 120 dB of ground stroke. This is 10 times more than a garbage truck or pneumatic jackhammer drill.

Can electricity kill people?

If you've ever thought about hitting lightning, you might assume that a lightning flicker will come down from the sky, hit you, and that's it. You are dead

First, lightning injures more people than falls. In fact, about 90 percent of those lightning hits survive, but often with long-lasting neurological damage, Drs. Says Mary Ann Cooper, a leading expert on electrical injuries.

"Secondly, lighting that strikes someone directly from the sky is called a direct attack," says meteorologist Ron Holle of Wesla Global Atmospheric, Inc., Tucson, Arizona, which rarely occurs.

You've probably heard that a building raid could hit a lighting wire or water pipe, killing a person talking on the phone or taking a bath. This happens, but such "contact attacks" are rare as direct attacks. Direct and contact attacks account for only 3-5 percent of electrical deaths and injuries in each account.

When an electric shock, which currently has 20,000 or more amperes, does not simply disappear in the earth as this electric current falls on the entire field. It spreads into the ground as a potentially lethal current with its voltage from where it hits.

And when lightning strikes the human animal, thousands of amps of current flows through the body. And it can cause a fatal accident. And a human can die.

Thanks for reading !!

What happens if I connect a DC voltmeter to measure AC voltage and vice versa?

A current of less magnitude than a DC meter will not harm it. Based on the construction of a DC voltmeter, it gives a reading of instantaneous values. Therefore when an AC wave passes near it, the pointer deflects at each moment of the wave. But when the wave moves as fast as 50 seconds per second, the meter will show the average value. AC meters, on the other hand, show RMS values ​​because the value of RMS is the AC wave that gives the same effect as DC.

To achieve this, the AC wave is corrected and the meter measures the effective average of the rectified wave. In better meters, the wave may be missed before measurement and square root. In a later version, the meter can take readings of any alternate waveform.

Methods of speed control of three phase induction motor

How to control the speed of a three-phase induction motor? The speed control method includes: changing the number of poles, stator voltage control, stator frequency change, cascade speed control, double-feed speed control, hydraulic coupler, electromagnetic slip clutch, etc.

The actual speed of the three-phase asynchronous motor is given by n = ns (1 - s) = 120f / p (1-s). It can be seen from the formula that the speed of a three-phase induction motor can be changed by changing the number of poles “p” of the induction motor, the slip “s” and the frequency of the power supply “f”.

The actual speed of 3-phase induction motor

Pole-variable speed controller

As shown in the formula ns = 120f / p, you can change the synchronous speed of the motor by changing the number of poles of the stator coil, thereby changing the running speed. Pole-shift speed control is most commonly used in squirrel-wheel induction motors. The pole-changing speed controller has the following characteristics:

Heavier mechanical properties and good stability

No-slip loss and high efficiency

Easy wiring, convenient control and low price

However, due to the large degree of difference, speed control cannot be achieved smoothly with this method. Therefore, it can be used with voltage speed control and electromagnetic slip clutch to obtain a more efficient smooth speed control characteristic.

This method is for step-less speed control manufacturing machines such as metal cutting machines, hoists, cranes, fans, water pumps and so on.

three-phase induction motor

Variable sliding speed control

1. Change the stator voltage

The torque of the induction motor is proportional to the square of the stator voltage. That is, changing the stator voltage can change the mechanical properties and torque of the motor.

This method is not suitable for a conventional squirrel-wheel motor because the rotor resistance is very small and the current increases rapidly at low speed.

But for a wound-type induction motor, it can be used in the rotor circuit using a series resistor or a common varistor to reduce the heat of the motor.

2. Change the rotor resistance

This speed control method is only applicable to the winding motor. In the rotor circuit of an induction motor with a series of resistors when the load is fixed, the higher the resistance, the lower the motor speed. The lower the resistance, the higher the speed.

This method is simple, easy to manage, and has low initial investment. However, the sliding energy is heated by the resistance. It also has soft mechanical properties.

3. Cascade speed control

Currently, cascade speed control uses the SCR inverter cascade control circuit and has the following advantages: stronger mechanical characteristics, low rectifier voltage drop, small space, no rotating part, low noise, easy maintenance. This is one of the speed control methods of the wound-type motor.

This also has its drawbacks. That is, the rotor circuit is equipped with a filter reactor, so the power factor is low.

Variable frequency speed control

According to the induction motor speed formula, it can be seen that when the slip s is constant, the speed n of the motor is essentially proportional to the power frequency f. Therefore, changing the frequency f can control the speed of the induction motor smoothly. Changing the power supply frequency is an economical speed control method and is one of the most popular ways to control the speed of an induction motor.

Variable frequency control allows you to change the power frequency of the motor stator and then change its synchronous speed. The main equipment of the variable frequency speed control system is the frequency converter or the variable frequency converter (VFD), which provides a frequency change to the power supply. Variable frequency drives can be divided into two categories: AC-DC-AC VFD and AC-AC VFD.

Three-phase induction motor and VFD

Today, widely used VFDs use digital technology and tend to be miniaturized, highly reliable, and highly accurate. It not only provides significant energy-saving performance for applications but also has the following performance:

 

• High precision, smooth speed control.
• Full protection function that can diagnose the fault with self-diagnosis and easy maintenance.
• Starting on a direct line, with high starting torque and low starting current, which reduce the impact on the electrical network and equipment and are provided with lifting torque, thus saving the soft starting device.
• High power factor and save the capacitor compensation device.

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Working Principle of Three Phase Induction Motor

How does a three-phase induction motor work? In short, it works based on the principle of electromagnetic induction. When the stator windings are supplied with three-phase alternating current, a rotating magnetic field is generated between the stator and the rotor. The rotating magnetic field cuts the rotor windings to generate induced electromotive force and current in the rotor circuit. The current in the rotor conductor forces the rotor to rotate under the effect of the rotating magnetic field. Below, we will specifically analyze the generation of the rotating magnetic field, its direction and speed, as well as the slip.

How does it generate a rotating magnetic field?

For three-phase induction motors, U / V / W windings with the same three-phase structure are placed in the stator core. Each phase of the winding differs spatially from an electrical angle of 120 degrees, as shown below, and the three-phase windings are provided with symmetrical three-phase AC, as shown in Figures (b) and (c) below. Here, take a 2-pole induction motor as an example to illustrate the location of the magnetic field in space like the current at different times.

three-phase winding in the star connection of the induction motor As shown in Figure (b) above, it is assumed that when the instantaneous current value is positive, it flows from the first ends of each winding and flows through the ends of the tail. On the contrary, it is when the current is a negative value.

As Figure (c) shows, when ωt = 0, iu = 0, the value of iv is negative and iw is positive. Then, the current of phase V flows from V2 and leaves V1, while the current of phase W flows from W1 and W2. According to the Ampere right-handed rule, the direction of the composite magnetic field produced by the three-phase current can be confirmed at the time ωt = 0, as shown in figure (d) ① below. It can be seen that the composite magnetic field is a pair of poles and the direction of the magnetic field is consistent with the direction of the longitudinal axis, that is, the top is the North Pole and the bottom is the South Pole.

symmetric three-phase current waveform diagrams ωt = π / 2, after a quarter cycle, the value of u changes from zero to maximum, and current flows from the first end U1 and exits the end U2. The iv value is still negative; therefore, the current direction of phase V is the same as shown in figure ①. iw also becomes negative and therefore the current of phase W is input and output W2. The direction of the compound magnetic field is shown in figure (d) ② that the direction of the magnetic field rotates clockwise by 90 ° compared to when ωt = 0.

Using the same analytical method, magnetic fields can be plotted when ωt = π, ωt = 2/3 * π and ωt = 2, as shown in (d) ③ ④ ⑤ respectively. Obviously, it is seen by the figure that the direction of the magnetic field gradually rotates in a clockwise direction, fully 360 °, that is, a rotation cycle.

2-pole winding rotating magnetic field diagram

It can be concluded as follows: the three-phase windings are placed in the stators of the three-phase motor in the same structure, but in the spatial position with an electrical angle difference of 120 degrees between them. As they are supplied separately with the three-phase AC, the composite magnetic field generated between the stator and the rotor rotates along the stator's inner circle, called the rotating magnetic field.

The direction of the rotating magnetic field

It is shown in the figure above that three-phase AC changes in the sequence of U-V-W phases, so the generated rotating magnetic field rotates clockwise in space. If the current phase sequence of the two-phase motor windings, such as U-W-V, is arbitrarily switched, it is practically proven that the rotating magnetic field generated must rotate counterclockwise. In conclusion, the direction of the rotating magnetic field depends on the phase sequence of the three-phase AC power supply in the winding. As long as the motor phase sequence is switched arbitrarily, the direction of the rotating magnetic field can be changed.

Magnetic field rotation speed and sliding

The example above is based on the 2-pole motor for illustration. If you want to obtain a 4-pole magnetic field, the number of coils will be doubled, as shown in figures (a) and (b) below. According to the analytical method above, the 4-pole rotating magnetic field diagram in space is shown in figure (c). Comparing the speed of rotation of the magnetic field in figure (c) with that of figure (d), as mentioned above, it is not difficult to discover that the speed of the magnetic field is not only related to the frequency of the power but also the number of poles.

Rotating magnetic field of 4-pole induction motor

Therefore, the speed of the rotating magnetic field is calculated by n1 = 120f1 / P, where it is:

n1 - the speed of the rotating magnetic field in rev / min

f1 - the frequency of the three-phase AC supply in Hertz

P - the number of poles

The speed of rotation of the magnetic field (n1) is also known as synchronous speed. The rotor speed of the three-phase induction motor (n) will not be accelerated to the speed of the rotating magnetic field (n1). Only in this way will there be a relative movement between the magnetic field of the winding and the rotating one to cut the magnetic lines. Thus, the induced electromotive force and current can be generated in the winding conductor of the rotor, producing the electromagnetic torque to make the rotor rotate continuously along with the direction of the rotating magnetic field. It can be seen that n ≠ n1 and n <n1 are a necessary condition for the operation of the induction motor, from which the name “asynchronous motor” derives. The difference between them is called "slip", which is expressed by the ratio between the difference and the synchronous speed: s = (n1-n) / n1.