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We’re going to be looking at inverters: their uses and how they work, coming up.
First of all look at the difference between alternating and direct current, then we’ll look at the purpose of inverters and where they are used. Then we’ll move on and have a look at simple example of how they work and finally we’ll look at a more advanced pulse width modulation example.
So, what is an inverter? well let’s start with the Basics. First of all, you probably know that there are two types of electrical power in use which are direct current or DC for shirred which is applied by batteries and solar panels etc.. now this type of power is mainly used by small digital goods with circuit boards etc.
The other type of power is alternating current or AC now this is supplied from the power sockets in your homes and this will typically be used to power larger appliances. Both of these types of power have their uses and limitations so we’ll often need to convert between the two to maximize their use.
An inverter is a device which is used to convert between direct current DC and alternating current AC, if you use an oscilloscope to look at the signal of these two types of power you will see that direct current sits at this maximum voltage and continues in a straight line, that’s because it’s current flows directly in only one direction which is why it’s called direct current, think of it: a bit like a river or a canal it’s always at its peak and it flows in just one direction. If you looks at alternating current you’ll see a wave-like pattern where the voltage alternates between its two peak voltages in both the positive half and then through to the negative half of its cycle, this is because the current travels back and forth.
It’s a bit like that of the ocean where it reaches its maximum high tide and then transitions through to his maximum low tide and in between the current of the sea, water will flow and change direction, so an inverter simply converts from direct current DC to alternating current AC and this is a very useful invention.
You can also convert from AC to DC using a rectifier and it’s common to find both of these in some devices, they will actually look at this in just a moment.
So where our inverters used well a common a fairly simple application of inverters is within solar panels or photovoltaic arrays, as these generate DC power but the appliances in your home will use AC power, so this needs to be converted for it to be of any use.
You can also buy portable inverters for your car which allow you to use the cars battery to power smaller household appliances. A slightly more complex way they are used is when integrated into variable frequency drives or variable speed drives to control the speed the torque and the direction of AC motors in order to achieve very precise control which saves energy.
You’ll find these on fans pumps and compressors and basically any equipment which rotates they are used in all industries but extensively. We’ve been HVAC systems for industrial and commercial properties.
In this application the inverter is coupled with a rectifier and the AC power which comes in is converted to DC and then back to AC, but the controllers will change the frequency of the sine wave pattern and by manipulating this, we can precisely control how the motor behaves and when you join this to a fare or compressor etc…Then you can precisely control how that performs also this is partly how the danfoss of tema + inverter condensing unit works it has a very clever control loop which is measuring the cooling load and then changes the speed of the motor, which changes the speed of the scroll compressor and that increases or decreases the cooling capacity to match the load, which was in precise temperature control as well as energy savings, so how do they work well? let’s consider a simplified circuit where the DC source is being used to power an AC load represented by the lamp to convert the DC to AC. We will use four switches, we will pair the switches together so that switches 2 and free/open when 1 and 4 close and vice versa. This will allow us to force the current through the AC load in an alternating direction so that the lamp will experience an alternating current even though it’s from a DC source.
First of all look at the difference between alternating and direct current, then we’ll look at the purpose of inverters and where they are used. Then we’ll move on and have a look at simple example of how they work and finally we’ll look at a more advanced pulse width modulation example.
So, what is an inverter? well let’s start with the Basics. First of all, you probably know that there are two types of electrical power in use which are direct current or DC for shirred which is applied by batteries and solar panels etc.. now this type of power is mainly used by small digital goods with circuit boards etc.
The other type of power is alternating current or AC now this is supplied from the power sockets in your homes and this will typically be used to power larger appliances. Both of these types of power have their uses and limitations so we’ll often need to convert between the two to maximize their use.
An inverter is a device which is used to convert between direct current DC and alternating current AC, if you use an oscilloscope to look at the signal of these two types of power you will see that direct current sits at this maximum voltage and continues in a straight line, that’s because it’s current flows directly in only one direction which is why it’s called direct current, think of it: a bit like a river or a canal it’s always at its peak and it flows in just one direction. If you looks at alternating current you’ll see a wave-like pattern where the voltage alternates between its two peak voltages in both the positive half and then through to the negative half of its cycle, this is because the current travels back and forth.
It’s a bit like that of the ocean where it reaches its maximum high tide and then transitions through to his maximum low tide and in between the current of the sea, water will flow and change direction, so an inverter simply converts from direct current DC to alternating current AC and this is a very useful invention.
You can also convert from AC to DC using a rectifier and it’s common to find both of these in some devices, they will actually look at this in just a moment.
So where our inverters used well a common a fairly simple application of inverters is within solar panels or photovoltaic arrays, as these generate DC power but the appliances in your home will use AC power, so this needs to be converted for it to be of any use.
You can also buy portable inverters for your car which allow you to use the cars battery to power smaller household appliances. A slightly more complex way they are used is when integrated into variable frequency drives or variable speed drives to control the speed the torque and the direction of AC motors in order to achieve very precise control which saves energy.
You’ll find these on fans pumps and compressors and basically any equipment which rotates they are used in all industries but extensively. We’ve been HVAC systems for industrial and commercial properties.
In this application the inverter is coupled with a rectifier and the AC power which comes in is converted to DC and then back to AC, but the controllers will change the frequency of the sine wave pattern and by manipulating this, we can precisely control how the motor behaves and when you join this to a fare or compressor etc…Then you can precisely control how that performs also this is partly how the danfoss of tema + inverter condensing unit works it has a very clever control loop which is measuring the cooling load and then changes the speed of the motor, which changes the speed of the scroll compressor and that increases or decreases the cooling capacity to match the load, which was in precise temperature control as well as energy savings, so how do they work well? let’s consider a simplified circuit where the DC source is being used to power an AC load represented by the lamp to convert the DC to AC. We will use four switches, we will pair the switches together so that switches 2 and free/open when 1 and 4 close and vice versa. This will allow us to force the current through the AC load in an alternating direction so that the lamp will experience an alternating current even though it’s from a DC source.
Solet’s give that a try if we leave switches two and three closed and then open switches 1 and 4 this will cause the current to flow through the right-hand side of the lamp if we then close which is 104 and open switches 2 and 3 this will force the current to flow with the left-hand side of the lamp so you can see that there is a direct current source but the lamp experiences an alternating current the lamp will not see this as a sine wave however as the sudden switching will only result in a square wave the sharp corners of the square wave can be damaging to electrical equipment so we need a way to smooth the corners out the switching is also far too fast for a human to do if you can see that the electricity you receive in the power sockets of your home this will be supplied at 50 or 60 Hertz depending on where in the world you are this means that the current needs to reverse direction 50 or 60 times per second so to achieve this we’ll use some special electronic components such as diyos IGBTs MOSFETs etc now if you don’t know how these components work don’t worry about that for now we’ll cover this in another video specifically for that for now just understand the circuits and how the current is controlled let’s look at a free phase example for a motor you can see this circuit has a DC source and an AC load and to convert the direct current into alternating current there are a bunch of these IGBTs which are connected to a controller the controller will send a signal to each a GPT telling it when to open and close these IGBTs are paired together so when the circuit is powered up you can see that the controller is switching pairs of IGBTs to allow current passed through them for a set amount of time so that the motor will experience an alternating current in this example the alternating current is in three phases so this is used to power the motor but how is it used to control the speed well if we take a closer look at the ITB TS we’ll see that they actually open and close in a pulsating manner multiple times per cycle this is known as pulse width modulation what’s happening is the cycle has been broken up into multiple smaller segments and the controller tells the igbts how long to closed for during each segment I’ve shown how this works in just one cycle for one phase of the free phase circuit just to keep it as simple as possible by opening and closing the switches at varying lengths of time during each segment of each cycle the igbts can allow varying amounts of current to flow through the circuit and into the motor the result of this is that the average power over each segment will result in a sine wave pattern the more segments the cycle is broken into the smoother the sine wave will be and the closed a will mimic a real AC sine wave so the motor will see the average value and will therefore experience a sine wave alternating current the controller can then change the amount of time the IGBTs are open to increase or decrease the frequency and the wavelength to control the motor speed torque and direction and we have a few additional control loops it can be used to exactly match the required loading to provide precise control of a system and unlock energy savings okay that’s it for today