How Alternators Work - Automotive Electricity Generator

[Applause] the alternator this device is an essential part of every combustion engine vehicle's electrical system so what does it do and how does it work that's what we'll be covering in this video which is sponsored by squarespace head to squarespace. com to start your free trial or use code engineering mindset to save 10 on websites and domains we find the alternator within the engine bay of the car the shaft of the alternator is connected to the engine via a belt and pulley when the engine is running the shaft of the alternator is forced to rotate this rotation generates electricity an alternator looks something like this the alternator produces a type of electricity known as aec or alternating current and this is why the unit is called an alternator with ac electricity the current of electrons flows forwards and backwards constantly this is the same type of electricity that you will find in the power outlets of your homes although the voltage in your homes will be much higher however all the electrical components within the car use another type of electricity known as dc or direct current with this type of electricity the electrons flow in just one direction this is the same type of electricity which we get from a battery so the alternator converts the alternating current into direct current via a rectifier the output voltage of the alternator varies with the speed of the car so the alternator also uses a regulator to limit this and maintain a near constant output every modern vehicle needs electricity to operate this is used to power things such as the lights the music system electric windows window wipers etc the engine combusts fuel this is used to turn the crankshaft and propel the vehicle along the engine only provides mechanical force it does not produce electricity so we need a way to power all the electrical devices within the vehicle and that's where the alternator comes in within the engine bay we also find a 12-volt lead-acid car battery this stores energy in the form of chemical energy it does not store electricity by the way we have covered how the car battery works in great detail do check that out links can be found in the video description down below when the engine is off the battery powers the car's electrical components this will drain the battery though when the car starts the battery provides a huge amount of current to the starter motor which turns the flywheel and starts the engine the battery is again partly drained during the startup because of the large current required to turn the starter motor once the engine is running the alternator is used to recharge the battery so that it has enough stored energy to start the engine again in future the alternator will also power the car's electrical devices while the engine is running but if the battery is left to discharge for too long then it will not be able to provide the large current necessary to start the starter motor and so the car will need to be jump started let's have a look at the main parts of the alternator at the front of the unit we find the pulley this is a wheel which has grooves cut into it to help grip the belt that provides a rotational force from the engine the pulley wheel is attached to the shaft which runs through the entire length of the alternator the internal components are held inside the main housing the housing consists of two parts the front and the rear bracket there are some slots cut into the casing to allow air to pass through and remove the unwanted heat which is generated at the back of the unit we have the electrical connections there are many different designs but this is an example of a simple three-wire design with an internal regulator and rectifier which has the following terminals first of all there's the b terminal this is the output of the alternator which charges the battery then we have the s terminal this allows the regulator to sense the voltage and then we have the f terminal this is connected to the ignition and provides the initial power to the electromagnet during startup to complete the circuit electricity flows back through the car's frame to and from the battery's negative terminal as this unit has an internal regulator and rectifier we find these components at the rear end of the unit which is usually under a protective cover we'll see those in more detail a little bit later in this video by removing the housing we can see inside the unit the first thing we see is the stator this data is stationary and does not rotate this consists of a number of laminated sheets which have a pattern of slots around the inner edge then we find three separate sets of copper wires which are wound between these slots in a certain order one end of each coil is connected together to form a neutral point this is a star configuration each coil set will produce a single phase of ac electricity providing three phases in total the other end of each coil passes through the case and attaches to the rectifier the alternator produces ac alternating current but the battery and the electrical devices of the car need direct current so the rectifier is going to convert the ac into dc electricity at the center of the alternator we find another coil of wire which is wound around an iron core and connected to the shaft the shaft also holds two slip rings the slip rings are connected to opposite ends of the coil within the rear housing we find some brushes these are some spring-loaded carbon blocks which are pushed outward to rub against the slip rings to form an electrical connection the car battery initially provides electricity to the coil via the brushes as the electricity passes through the coil it generates an electromagnetic field to enhance this electromagnetic field two iron claws are placed either end of the coil which will interlock with each other one end will become the north pole and the other will become the south pole as the electromagnet is attached to the rotor shaft when the engine turns the shaft it also rotates the electromagnet past the coils of the stator this will cause the stator coils to generate a current and so electricity is generated once the alternator is generating electricity the alternator is able to power the electromagnet by itself via a diode trio which converts the three-phase ac into dc the voltage and current produced by the alternator will vary with the speed of the vehicle the faster the vehicle travels the faster the crankshaft rotates and so the faster the alternator also rotates this increases the voltage and current to control this another component is used called the regulator which is mounted at the rear of the unit this is an integrated circuit board which monitors the output of the alternator and varies the current flowing through the electromagnet to control its strength the strength of the electromagnet can be used to vary the output from the alternator electricity is the flow of electrons in a wire the copper wire is made from millions and millions of copper atoms each atom has a free electron this is an electron which is able to move freely between other atoms it does move two other atoms by itself but this occurs randomly in any and all directions which is of no use to us we need lots of electrons to flow in the same direction and we do that by applying a voltage difference across the two ends of a wire this forces the electrons to flow if we reverse the battery the electrons flow in the opposite direction when electricity passes through a wire an electromagnetic field is generated around the wire if we place some compasses around the wire and pass a current through it the compasses will align with the magnetic field if we reverse the direction of current the magnetic field reverses and the compasses change direction if the wire is wrapped into a coil the magnetic field becomes stronger each cross section of wire still produces an electromagnetic field but they combine together to form a larger stronger magnetic field the electromagnet produces a north and south pole just like a permanent magnet if we increase the current to the coil the electromagnetic field increases we can also do the opposite if we pass a magnet through a coil of wire a current is generated in the coil the dial on the ammeter indicates a current flowing in the forward direction this is therefore generating a dc or direct current when the magnet stops moving the dial returns to zero when the magnet is moved in the opposite direction the current flows in the opposite way and the dial indicates a reverse current if we move the magnet in and out repeatedly the current will therefore alternate between flowing forwards and backwards this is how ac or alternating current is generated the current is continuously alternating in direction if we move the magnet faster a stronger current is generated if we use a stronger magnet then the current also increases if we use a larger coil with more turns then this will also generate a larger current instead of using a permanent magnet we could use an electromagnet as we move this in and out it will also generate an ac current in the coil but with the electromagnet we can adjust the current and voltage to vary the strength of the magnetic field this lets us control how much current is generated in the coil instead of moving a magnet in and out of a coil we can generate a current much easier by rotating the magnet and placing the coils around this the strongest part of the magnetic field is at the ends where the magnetic field lines converge you can see the magnetic field lines by sprinkling iron filings over the magnet with the magnet between the two coils there is no current generated but as the magnet starts to rotate the strongest part of the magnetic field gets closer and closer to the coil the coil experiences a changing intensity of the magnetic field this will cause more and more electrons to be pushed forwards up until its maximum intensity then the magnet starts to move away from the coil so the magnetic field begins to decrease and so does the current of electrons until it reaches zero again and now the opposite end of the magnet begins to get closer to the coil and this pulls the electrons in the opposite direction this again reaches a maximum point and then decreases back to zero and so if we were to plot this current on a chart we would get a sine wave with a current flowing in the positive and then the negative regions this setup gives us a single phase ac supply but we have all this empty space between the coils which seems a bit of a waste so what can we do with all this space well we can add more coils to create more phases and provide even more power if we place another coil 120 degrees rotation from the first phase this will give us a second phase why because the coil is at a different angle so it will experience the change in intensity of the magnetic field at a different time the current is therefore going to flow forwards and backwards at a different time that gives us another sine wave which occurs at a different time we still have empty space here so we can add another set of coils at 120 degrees from the previous set to create a third phase if we use just a single phase then for every rotation of the magnet half the time the current is flowing forwards and half the time the current is flowing backwards but with three phases we always have a phase which is flowing forwards and we always have a phase which is flowing backwards which means we can utilize this to provide more power instead of having three separate coils and six wires as the phases are always switching between forwards and backwards we can connect the ends of the coils together the current will then flow freely between each coil as it changes direction now we are producing three-phase ac electricity but all of our electrical circuits and components within the car use dc or direct current so we need a way to convert ac to dc and for that we use a full bridge rectifier this is essentially just six diodes connected in pairs and wired in parallel diodes only allow current to flow in one direction and they block the current in the reverse direction with a single phase supply for every turn of the magnet current will only flow for half of the term the other half will be completely blocked if we connected each of the three phases separately to a diode then the current will flow or be blocked at different times therefore we can combine these phases into a block of diodes and only the phase nearest its maximum will be allowed to pass through this gives us a slightly rippled dc output to smooth this ripple out we can connect a capacitor which will basically absorb electrons and then eject electrons automatically to maintain a constant output this gives us a constant smooth dc supply by the way we have covered diodes capacitors and power inverters in great detail previously do check those videos out links can be found in the video description down below okay so now we have a dc output but if the magnet is connected to the engine and the car speeds up then the magnet will spin faster and that will increase the output voltage and current we don't want that because it will kill all of our electronic components within the car so we need a way of regulating the voltage if you remember we saw that by using an electromagnet we can increase or decrease electromagnetic field strength by varying the voltage and by varying the strength of the magnet we can vary the voltage and current generated in the coil that's why the alternator uses an electromagnet so that it can control the output the car battery powers electromagnet although most modern alternators will use a diode trio which converts the alternating current of the alternator into direct current and powers the electromagnet via a voltage regulator once the alternator is generating electricity on the power supply of the electromagnet within the regulator we find a component known as a transistor the voltage sensor is also connected to the regulator the transistor is a type of electronic switch which can be turned on and off thousands of times per second by a controller this can be used to control the amount of current flowing if we imagine that the current flowing through the coil from the battery is at its maximum level for a given period of time then we get 100 current and the electromagnet is at 100 of its strength if the car speeds up then the magnet will spin faster and that will increase the output voltage and current but if we now control the switch so that electricity is only flowing for half of the time then we get 50 percent of the current and therefore the electromagnet is only 50 of its strength so by measuring the output of the alternator and then varying the open and close times of the transistor switch we can control the current flow through the coil and the strength of the electromagnet this controls how strong the electromagnet will be which affects how much electricity is produced this produced electricity charges the battery but now that you are all charged up check out squarespace. com to create your own online web presence which is packed with features to empower individuals to launch share and promote their own projects there's powerful blogging tools to showcase your project photos videos and progress updates you can easily schedule appointments for classes and sessions with team members or clients all through their inbuilt tools and you can even collect payments or donations to help support your cause head to squarespace.

com for a free trial and when you're ready to launch go to squarespace. com forward slash engineering mindset to save 10 of your first purchase of a website or a domain okay guys that's it for this video but to continue your learning then check out one of the videos on screen now and i'll catch you there for the next lesson don't forget to follow us on facebook instagram linkedin as well as the engineeringmindset.