Such power systems consist of multiple rectifiers that convert AC power to DC power, so they can operate. Without the right rectifier, there is little chance of configuring your ideal system. They are the heart of a power system as they offer optimised solutions for each application.
Using rectifiers means that you can tailor your power system without having to rebuild every element. So, it is clear that rectifiers are a key component to any network system but we need to dip deeper to understand the carious types. Depending on the situation, different rectifiers are used conditional to the system it is used in. The top two levels are single phase and three phase, which indicate how many diodes are used in the circuit.
Then we come to half wave, full wave and bridge rectifiers, which affect what half cycles are produced. Single phase rectifiers have an input of one phase AC power. The structures are very simple, needing one, two or four diodes dependent on the type of system. This means that the single phase rectifier delivers a small amount of power and has less transformer utilisation factor TUF. A single phase rectifier uses only single phase of transformer secondary coil for the conversion and diodes are connected to the secondary winding of single phase transformer.
This causes high ripple factor. Three phase rectifiers have an input of three phase AV power. Structures need three or six diodes and these are connected to each phase of the transformer secondary winding. Three phase rectifiers are used in place of single phase rectifiers to reduce ripple factor. Comparing the two types of rectifiers, three phase is preferred when using large systems.
This is because they can deliver large amounts of power and do not require any additional filter to reduce ripple factor. Because of this, three phase rectifiers are more efficient and have more transformer utilisation factor. Half wave rectifiers convert one half cycle on the AC input into pulsating DC output. This allows half cycle of the AC input while blocking the other half cycle. The half cycle can be either positive or negative. It is the simplest rectifier as only one single diode is used.
Figure 1 below shows a positive half wave rectifier whereas a negative half wave rectifier would show the diode being reverse biased facing the opposite way. Due to the pulsating nature of the direct current, ripple factor is high. This means that half wave rectifiers are not considered to be efficient and they often need filters to reduce ripple factor.
Output can be smoothly controlled in a controlled rectifier. The time required to design a controlled rectifier is more compared to the time required to build an uncontrolled rectifier. Uncontrolled rectifier uses diode as a ac to dc conversion semiconductor devices.
Controlled rectifier uses SCR silicon control rectifier and output can be controlled by governing the firing angle of SCRs. Your Email. Your Name. Chetan Shidling Staff asked 2 years ago. I need short information. Chetan Shidling. Hence the diode is forward biased. Under the forward biased condition, the diode acts like a closed switch resulting in current flowing through the diode. Hence the diode is reverse biased and acts as an open switch.
No current flows through the diode or circuit. The half wave rectifiers produce too much of ripples and the output current is not continuous. Ripples and efficiency can be improved using full wave rectifiers.
In full wave rectifiers we can obtain output voltage during the positive and negative half cycles. Therefore it delivers improved efficiency than the half wave rectifiers. It produces an output voltage that is purely DC.
For the full wave rectifiers the average direct current output voltage is higher than that of half wave, the output of the full wave rectifier has much less ripple than that of the half wave rectifier producing a smoother output waveform.
In a single phase, Full Wave uncontrolled Rectifier circuit two diodes are now used. Only one diode will be forward biased and conducts during each half cycle. A centre tapped transformer is used in full wave rectifier as shown in the figure. As mentioned earlier, the voltage ripples can be controlled by connecting a smoothing capacitor in parallel to the load. It converts the full wave rippled output of the rectifier into a smooth DC output voltage.
But the usage of the capacitor is the circuit is limited by the cost factors and the size of the circuit. The smoothing capacitor controls the ripple as follows:.
Commonly used smoothing capacitors are of uF or higher of aluminium electrolytic type. The parameters considered during the selection of appropriate capacitance value are its working voltage and capacitance value, which determines the number of ripples that appear at the output.
The direct voltage obtained after rectifications contains a certain amount of voltage ripples that can be reduced by using a large value of capacitance. For half-wave rectifiers, it is not necessary. This is because in half-wave rectifier will increase the ripple rather than reducing it. Half-wave rectifiers are not practically used in a circuit due to its reduced efficiency and more losses.
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