ClassX Video Lessons Youtube Channel The Engineering Mindset Transformers Explained – How transformers work
Transformers are fascinating devices that play a crucial role in our everyday lives. They help connect our homes to power stations, ensuring we have the electricity we need. In this article, we’ll dive into how transformers work, why they make noise, and how to calculate their values.
Transformers are devices used to transfer electrical energy between circuits, changing the voltage and current in the process. They only work with alternating current (AC) and are rated in volt-amps (VA) or kilovolt-amps (kVA), unlike most appliances, which are rated in watts or kilowatts.
Transformers come in various sizes, from small ones in doorbells and laptop chargers to massive ones that power entire cities. They consist of two separate coils of wire wrapped around an iron core. The primary side is connected to the power source, and the secondary side is connected to the device needing power.
Transformers can either increase (step-up) or decrease (step-down) voltage. For example, power stations might generate 12,000 volts, but our homes need between 120 and 240 volts. To reduce energy loss during transmission, a step-up transformer increases the voltage to around 400,000 volts. As electricity reaches towns, step-down transformers reduce it to around 11,000 volts for local distribution and then further down to 240 volts for homes.
By increasing voltage, transformers reduce current, minimizing energy loss in cables. Energy loss depends on the current and the resistance of the cable. For instance, sending 10 kilowatts through a cable with 5 ohms of resistance at 240 volts would result in significant energy loss. However, at 400,000 volts, the losses are minimal due to the lower current.
When an electrical current flows through a wire, it creates a magnetic field. If the current direction changes, so does the magnetic field. Connecting an AC generator to a wire loop causes the magnetic field to push and pull electrons, making them alternate direction and creating a sine wave pattern. This can be observed using an oscilloscope.
The frequency of the input and output remains the same; transformers only change voltage, not frequency. Wrapping the wire into a coil strengthens the magnetic field, and insulating the wire ensures the current flows correctly.
Placing a second coil near the first allows the changing magnetic field to induce voltage in the second coil, which is the principle behind transformers. This process only works with AC. Direct current (DC) would not induce voltage in the secondary coil, except briefly when the switch is opened or closed.
A ferromagnetic iron core between the coils concentrates the magnetic field, improving efficiency. However, this can cause energy losses due to eddy currents, which are minimized by using laminated sheets for the core.
Transformers are classified as step-up or step-down based on the number of wire turns on the secondary side. A step-up transformer has more turns on the secondary side, increasing voltage and decreasing current. Conversely, a step-down transformer has fewer turns, reducing voltage and increasing current.
The power on both sides of a transformer must remain the same, which is why we use volt-amps instead of kilowatts. Transformers transfer power between coils, and the actual power depends on the connected devices.
Transformers are also used in rectifier circuits to convert AC into DC. The transformer first reduces the voltage, and then diodes convert this into a rough DC, which is smoothed out by a capacitor.
Let’s do some basic calculations. Assume a perfect transformer with no losses, 1,000 turns on the primary, and 100 turns on the secondary. If we supply it with 120 volts, we can calculate the output voltage on the secondary side. If we only know the output voltage and the number of turns, we can find the input voltage using the appropriate formula. Similarly, we can determine the number of turns on either side based on the voltages and currents.
Explore additional resources to continue learning about electrical engineering and deepen your understanding of transformers.
Gather materials like insulated wire, an iron nail, and a battery to create a basic transformer model. Wrap the wire around the nail to form two separate coils. Connect one coil to the battery and observe how the magnetic field affects the other coil. This hands-on activity will help you understand the basic principles of how transformers work.
Using a simulation tool or a safe lab setup, experiment with different numbers of wire turns on the primary and secondary coils. Measure the input and output voltages to see how changing the number of turns affects the voltage transformation. This will reinforce your understanding of step-up and step-down transformers.
Calculate energy loss in transmission lines using different voltage levels. Use the formula for power loss (P = I²R) to see how increasing voltage reduces current and minimizes energy loss. This activity will help you appreciate the efficiency of transformers in power distribution.
Use iron filings and a magnet to visualize magnetic fields. Place the filings on a sheet of paper over a magnet to see the field lines. Relate this to how transformers use magnetic fields to transfer energy between coils. This visual activity will deepen your understanding of the science behind transformers.
Research different materials and designs to improve transformer efficiency. Present your findings on how laminated cores and other innovations reduce energy losses. This research activity will enhance your knowledge of transformer technology and its real-world applications.
Sure! Here’s a sanitized version of the transcript, removing any promotional content and maintaining a focus on the educational aspects:
—
This is a transformer. We find them everywhere, and they are essential to our modern lifestyle. They provide the connection between our homes and electrical power stations. In this video, we will explore how transformers work, why they make noise, and how to calculate their values.
Transformers look something like this and are illustrated with symbols in electrical drawings. They are devices used to transfer electrical energy, changing the voltage and current in the process. However, they only work with alternating current (AC) and do not work with direct current (DC). Most appliances are rated in watts or kilowatts, but transformers are rated in volt-amps (VA) or kilovolt-amps (kVA).
We can find small transformers used in doorbells or laptop chargers, larger versions to supply homes and businesses, and enormous ones that supply entire regions of towns and cities.
There are various ways to construct a transformer, but they essentially consist of two separated coils of wire wrapped around an iron core. The generator or supply is connected to one coil, known as the primary side, and the load, which is the device needing power, is connected to the other coil, known as the secondary side.
Electricity is dangerous, so do not attempt to disassemble transformers unless you are qualified and competent.
If we use a step-up transformer, we can increase the voltage on the output. Conversely, a step-down transformer decreases the voltage. For example, a power station might produce 12,000 volts, but your home needs between 120 and 240 volts. To minimize energy loss during transmission, we use a step-up transformer to increase the voltage to around 400,000 volts. As we reach the town, we use a step-down transformer to reduce this back to around 11,000 volts for local distribution, and then again down to around 240 volts for our homes.
By increasing the voltage through a transformer, we reduce the current, which helps minimize energy loss in the cables. Energy loss depends on the electrical current and the resistance of the cable. For instance, if a cable has 5 ohms of resistance and we try to send 10 kilowatts through it at 240 volts, we would lose a significant amount of energy due to high current. However, if we send this at 400,000 volts, the losses are minimal because the current is low.
In North America, homes can have either 120 or 240 volts due to a three-wire system, while most of the world uses around 230 volts with a simpler two-wire system.
When we pass an electrical current through a wire, it generates a magnetic field around the wire. If we reverse the direction of the current, the magnetic field also reverses. When we connect an AC generator to a closed loop of wire, the magnetic field inside the generator pushes and pulls the electrons in the wire, causing them to constantly alternate direction. This results in a sine wave pattern, which can be observed using an oscilloscope connected to a power outlet.
The frequency of the input is the same as the output; we can only increase or decrease the voltage, not the frequency. When we wrap the wire into a coil, the magnetic field becomes stronger. The wire must be insulated to ensure the current flows along its entire length.
If we place a second coil of wire near the first coil, the changing magnetic field will induce a voltage in the second coil. This is the principle behind transformers. The key component is the constantly changing magnetic field, which disturbs the free electrons and causes them to move, creating electromotive force.
This process only works with alternating current. If we connect a direct current supply to the transformer, the magnetic field will be constant and will not induce a voltage in the secondary side. The only time it will create an electromotive force using direct current is briefly when the switch is opened and closed, which changes the magnetic field.
To improve efficiency, a ferromagnetic iron core is placed between the coils to concentrate the magnetic field. However, this can lead to energy losses due to eddy currents, which are minimized by using laminated sheets for the core.
Transformers can be classified as step-up or step-down based on the number of turns of wire on the secondary side. A step-up transformer has more turns on the secondary side, increasing voltage and decreasing current, while a step-down transformer has fewer turns, reducing voltage and increasing current.
The power on both sides of the transformer must remain the same, which is why we use volt-amps instead of kilowatts. The transformer simply transfers power between the coils, and the actual power depends on what is connected to it.
Transformers are also used in rectifier circuits to convert alternating current into direct current. The transformer first reduces the voltage, and then diodes convert this into a rough direct current, which is smoothed out by a capacitor.
Let’s run some basic calculations for transformers. Assuming a perfect transformer with no losses, if we have a transformer with 1,000 turns on the primary and 100 turns on the secondary, and we supply it with 120 volts, we can calculate the output voltage on the secondary side.
If we only know the output voltage and the number of turns, we can find the input voltage using the appropriate formula. Similarly, we can find the number of turns on either side based on the voltages and currents.
Check out additional resources to continue learning about electrical engineering.
—
This version focuses on the educational content while removing promotional elements and maintaining clarity.
Transformers – Devices that change the voltage of an electric current, typically used to increase or decrease voltage levels in power lines. – Transformers are essential in power distribution systems to adjust voltage levels for safe and efficient electricity transmission.
Voltage – The electric potential difference between two points, which causes electric current to flow in a circuit. – The voltage across the battery terminals determines how much current flows through the circuit.
Current – The flow of electric charge through a conductor, typically measured in amperes. – When the switch is closed, the current flows through the circuit, lighting up the bulb.
Energy – The capacity to do work, which in physics is often transferred or converted from one form to another. – The energy stored in the battery is converted into light and heat when the flashlight is turned on.
Magnetic – Relating to or exhibiting magnetism, a force that can attract or repel certain materials like iron. – The magnetic field around a magnet can influence the direction of a compass needle.
Coils – Loops of wire that can generate a magnetic field or induce voltage when current passes through them. – The coils in an electric motor create a magnetic field that turns the rotor.
Efficiency – The ratio of useful energy output to the total energy input, often expressed as a percentage. – Improving the efficiency of a machine means it can do more work with the same amount of energy input.
Alternating – Referring to a type of current that periodically reverses direction, commonly used in household power supplies. – Alternating current is used in homes because it is more efficient for long-distance power transmission.
Resistance – The opposition to the flow of electric current, causing energy dissipation as heat, measured in ohms. – The resistance of a wire affects how much current can flow through it for a given voltage.
Circuits – Paths through which electric current flows, typically consisting of a power source, conductors, and a load. – In a series circuit, all components are connected end-to-end, so the same current flows through each component.
