3 phase rectifier working

Rectification is basically the process in which we convert AC signal into DC signal. An AC signal has two cycles a positive and a negative cycle. But a DC only has a positive cycle. But most of you already know what I'm speaking of and many of you know a lot more than this. You can find detail of rectification on Wikipedia. We are here to discuss three phase rectifiers. Well these are not used in basic electronics projects as it is seen mostly on industrial level.

When there is need of rectifying three phase AC, we use a three phase rectifier. Basically a rectifier eliminates the negative cycle of AC, so by principle we can get a much better result if we do rectification another time. There are two basic types of three phase rectifiers, 6 pulse rectifiers and 12 pulse rectifiers. Both of them are shown here below. Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson. Basic soldering is needed here.

Just solder the circuit all together. This is simple enough and only basic skill level is required. For an uncontrolled three-phase bridge rectifier, six diodes are used, and the circuit again has a pulse number of six.

For this reason, it is also commonly referred to as a six-pulse bridge. For low-power applications, double diodes in series, with the anode of the first diode connected to the cathode of the second, are manufactured as a single component for this purpose.

Some commercially available double diodes have all four terminals available so the user can configure them for single-phase split supply use, half a bridge, or three-phase rectifier. Although better than single-phase rectifiers or three-phase half-wave rectifiers, six-pulse rectifier circuits still produce considerable harmonic distortion on both the AC and DC connections. For very high-power rectifiers the twelve-pulse bridge connection is usually used.

This cancels many of the characteristic harmonics the six-pulse bridges produce. The 30 degree phase shift is usually achieved by using a transformer with two sets of secondary windings, one in star wye connection and one in delta connection.

Reply 3 years ago. Your best bet is to make a three phase generator from a three phase motor. Just watch out what coupling it's using although you'll be able to change it, most likely. Looks like the first stage of a Variable Frequency Drive - convert your three phase to DC and then re-invert it with PWM to control speed and torque of a three-phase motor!

Introduction: 3 Phase Rectifier 6 and 12 Pulse Reactifier. By syedhamzahasan Follow.You may wonder how power lines send electric currents across long distances for different purposes. And there are different "types" of electricity. The electricity that powers electric railway systems may not be appropriate for household appliances like phones and television sets.

Rectifiers help by converting between these different types of electricity. Rectifiers let you convert from alternating current AC to direct current DC. AC is current that switches between flowing backwards and forwards at regular intervals while DC flows in a single direction.

They generally rely on a bridge rectifier or a rectifier diode. All rectifiers use P-N junctionssemiconductor devices that let electric current flow in only a single direction from the formation of p-type semiconductors with n-type semiconductors.

The "p" side has an excess of holes locations where there are no electrons so it is positively charged. The "n" side is negatively charged with electrons in their outer shells. Many circuits with this technology are built with a bridge rectifier.

Bridge rectifiers convert AC to DC using its system of diodes made of a semiconductor material in either a half wave method that rectifiers one direction of the AC signal or a full wave method that rectifies both directions of the input AC. Semiconductors are materials that let current flow because they're made of metals like gallium or metalloids like silicon that are contaminated with materials like phosphorous as a means of controlling current.

You can use a bridge rectifier for different applications for a wide range of currents. Bridge rectifiers also have the advantage of outputting more voltage and power than other rectifiers. Despite these benefits, bridge rectifiers suffer from having to use four diodes with the extra diodes compared to other rectifiers, causing a voltage drop that decreases the output voltage. Scientists and engineers generally use silicon more frequently than germanium in creating diodes. Silicon p-n junctions work more effectively at higher temperatures than germanium ones.

Silicon semiconductors let electric current flow more easily and can be created with lower costs. These diodes take advantage of the p-n junction to convert AC to DC as a sort of electric "switch" that lets current flow in either the forward or reverse direction based on the p-n junction direction. Forward biased diodes let current continue to flow while reverse biased diodes block it.

This is what causes silicon diodes to have a forward voltage of about 0. For germanium diodes, the forward voltage is 0. The anode terminal of a battery, electrode or other voltage source where oxidization occurs in a circuit, supplies the the holes to the cathode of a diode in forming the p-n junction.

In contrast, the cathode of a voltage source, where reduction occurs, provides the electrons that are sent to the anode of the diode. You can study how half wave rectifiers are connected in circuits to understand how they work. Half wave rectifiers switch between being forward biased and reverse biased based on the positive or negative half cycle of the input AC wave.

It sends this signal to a load resistor such that the current flowing through the resistor is proportional to voltage. You can measure the voltage across the load resistor as the supply voltage V swhich is equal to the output DC voltage V out. The resistance associated with this voltage also depends on the diode of the circuit itself. Then, the rectifier circuit switches to being reverse biased in which it takes the negative half cycle of the input AC signal.

In this case, no current flows through the diode or the circuit and the output voltage drops to 0. The output current is, then, unidirectional.

Full wave rectifiers, in contrast, use the entire cycle with positive and negative half cycles of the input AC signal. The four diodes in a full wave rectifier circuit are arranged such that, when the AC signal input is positive, the current flows across the diode from D 1 to the load resistance and back to the AC source through D 2.

When the AC signal is negative, the current takes the D 3 -load- D 4 path instead. The load resistance also outputs the DC voltage from the full wave rectifier.

Most of the electronic appliances in your household use AC, but some devices like laptops convert this current to DC before using it.Now we come to the most popular application of the diode : rectification.

Simply defined, rectification is the conversion of alternating current AC to direct current DC. This involves a device that only allows one-way flow of electric charge. As we have seen, this is exactly what a semiconductor diode does. The simplest kind of rectifier circuit is the half-wave rectifier. It only allows one half of an AC waveform to pass through to the load. Figure below. For most power applications, half-wave rectification is insufficient for the task.

Furthermore, the AC power source only supplies power to the load one half every full cycle, meaning that half of its capacity is unused. Half-wave rectification is, however, a very simple way to reduce power to a resistive load.

Because the half-wave rectified power pulses far more rapidly than the filament has time to heat up and cool down, the lamp does not blink. Instead, its filament merely operates at a lesser temperature than normal, providing less light output. Since the controlling device the diode, in this case is either fully conducting or fully nonconducting at any given time, it dissipates little heat energy while controlling load power, making this method of power control very energy-efficient.

This circuit is perhaps the crudest possible method of pulsing power to a load, but it suffices as a proof-of-concept application. If we need to rectify AC power to obtain the full use of both half-cycles of the sine wave, a different rectifier circuit configuration must be used. Such a circuit is called a full-wave rectifier. One kind of full-wave rectifier, called the center-tap design, uses a transformer with a center-tapped secondary winding and two diodes, as in the figure below.

Full-wave center-tap rectifier: Top half of secondary winding conducts during positive half-cycle of input, delivering positive half-cycle to load. During the next half-cycle, the AC polarity reverses. Full-wave center-tap rectifier: During negative input half-cycle, bottom half of secondary winding conducts, delivering a positive half-cycle to the load. One disadvantage of this full-wave rectifier design is the necessity of a transformer with a center-tapped secondary winding.

If the circuit in question is one of high power, the size and expense of a suitable transformer is significant. Consequently, the center-tap rectifier design is only seen in low-power applications. The full-wave center-tapped rectifier polarity at the load may be reversed by changing the direction of the diodes.

Furthermore, the reversed diodes can be paralleled with an existing positive-output rectifier. The result is dual-polarity full-wave center-tapped rectifier in the figure below. Note that the connectivity of the diodes themselves is the same configuration as a bridge. Another, more popular full-wave rectifier design exists, and it is built around a four-diode bridge configuration. For obvious reasons, this design is called a full-wave bridge.Home About Contact-us. How three-phase bridge rectifier works?

Rectifier is a device that converts Ac voltage into DC voltage. For economics of generation and transmission of power. The electric power is usually available in an AC. The AC voltage varies sinusoidal with the time and had a frequency of 50Hz or 60Hz depending upon the country.

This AC power is used for lighting purposes, for heating and to run an electric induction motor. How diodes work? Uncontrolled Three Phase bridge Reactfier working : Three phase bridge rectifier. Diode group D1, D3, D5 conducts for positive voltage cycle. When the voltage of phase L1 reaches its positive peak value, terminal A takes on the value of phase L1. In the same way diodes group D4, D6, D2 conducts for the negative half cycle. The DC output voltage of the uncontrolled bridge rectifier is constant and represents the difference between the voltages of the two diode groups.

The average value of the pulsating DC voltage is approximately 1. Fully-controlled Three Phase Rectifiers working: Fully-controlled three-phase rectifier As seen in the above diagram Fully-controlled bridge rectifiers use thyristors instead of a diode as in uncontrolled bridge rectifier.

However, the difference between diode and the thyristor is that the thyristor has a third terminal called the gate G. When the firing pulse is provided to the third terminal gate, the thyristor will conduct. Once current starts flowing through the thyristor, it will continue conducting until the current drops to zero. The current cannot be interrupted by sending a signal to the gate. Thyristors are used in rectifiers. The degree value indicates the delay between the voltage zero-crossing and the time when the thyristor is triggered.

In all other respects, fully controlled rectifiers working is the same as uncontrolled rectifiers. What is Auto-transformer Starter,Working principle,diagram,advantages March 25, Star Delta Starter? Working principle,Theory, Circuit Diagram January 22, What is corona effect? Why single-phase induction motor is not self-starting-reason,make self starting?

April 01, Menu Footer Widget. Home Privacy policy Terms of service Disclaimer About. Fully-controlled three-phase rectifier.In electronics, Rectifier circuit is the most used circuit because almost every electronic appliance operates on DC Direct Current but the availability of the DC Sources are limited such as electrical outlets in our homes provide AC Alternating current. Even our cell phone chargers use rectifiers to convert the AC from our home outlets to DC.

Different types of Rectifiers are used for specific applications. We mainly have two types of voltage types present that are widely used these days. They are alternating and direct voltage types. These voltage types can be converted from one type to another using special circuits designed for that particular conversion.

These conversions happen everywhere. Our main supply which we get from power grids are alternating in nature and the appliances we use in our homes generally require a small DC voltage.

This process of converting alternating current into direct current is given the name rectification. One of the most common part of an electronic power supply is a bridge rectifier. Many electronic circuits require rectified DC power supply for powering various electronic basic components from available AC mains supply.

The simple bridge rectifier is used in a variety of electronic AC based power devices. Another way to look at the rectifier circuit is that, it can be said to convert currents instead of voltages. Concisely, a rectifier take a current which has both negative and positive components and rectifies it such that only the positive component of the current remains. Bridge rectifiers are widely used in power supplies that provide necessary DC voltage for the electronic component or devices.

The most efficient switching devices whose characteristics are known fully are diodes. In theory any solid-state switch which can be controlled or cannot be controlled can be used instead of the diodes.

Usually, the types of Rectifier s are classified based on their output.

Rectifier Circuits

In this article, we will discuss many types of Rectifiers such as:. A Rectifier is an electrical device that is made of one or more than one diodes that converts the alternating current AC into direct current DC. It is used for rectification where the process below shows that how it convert AC into DC. Rectification is the process of conversion of the alternating current which periodically changes direction into direct current flow in a single direction.

There are mainly two types of rectifiers:. Bridge rectifiers can be broadly classified into single and three phase rectifiers based on the type of input they work on. Both of these types include these further classifications which can be made into both single and three phase rectifiers.

3 phase rectifier working

The further classification is based on the switching devices the rectifier uses and the types are uncontrolled, half controlled and full controlled rectifiers. Some of the types of rectifiers are discussed below. Based on the type of rectification circuit does, the rectifiers are classified into two categories.

Bridge rectifier is the most commonly used rectifier in electronics and this report will deal with the working and making of one.In polyphase rectifier we will be discussing in detail the working, the input and the output wave forms of a three phase half wave rectifier and three phase full wave rectifier, along with the connections of an interface transformer on a 6-diode rectifier.

A three phase half wave rectifier, as the name impliesconsists of a three phase transformer. Given below is a star connected secondary three phase transformer with three diodes connected to the three phases. The input and the output wave forms for the circuit above is shown below. For each one-third of the cycle, each diode conducts. This process repeats for each of the three diodes. DC output voltage of three phase half wave rectifier is given below.

The arrangement shown above is practised only if 3 phase supply is available. Like in single phase circuits, there is not a single point at which the rectified voltage will drop to zero, even without a smoothing arrangement. The voltage ripples are also small when compared to single phase circuits and the frequency of ac supply is three times more when compared with the former.

If smoothing is needed, it can be obtained easily. The circuit will need a zig-zag secondary if dc saturation of transformer core which is caused by the flow of direct current of each diode, is to be avoided. A three phase full wave rectifier can also be called a six wave half wave rectifier. As shown in the output wave form, the fluctuation of dc voltage is less in a three phase circuit. The variation lies between the maximum alternation voltage and Six diodes are used for the making of this full wave rectifier.

As so, it may pose some problems and may also be advantageous in some cases. If we need a smoother output, the use of six diodes may be seen as an advantage. But the use of six diodes complicates the circuit and each diode operates for a shorter cycle. Also, since no more than six are used, the circuit is cost effective, as long as it is compared with the comparative increase in the output of the rectifier.

As told earlier, out of the six diodes, only one diode conducts at a particular instant.Definition: A 3 Phase rectifier is a device which rectifies the input AC voltage with the use of 3 phase transformer and 3 diodes which are connected to each of the three phases of transformer secondary winding.

A single phase rectifier also rectifies i. And the diodes are connected to the secondary winding of single phase transformer. The drawback of this arrangement is high ripple factor. In case of half wave rectifier the ripple factor is 1. In both the cases the value of ripple factor cannot be neglected. While in case of half wave rectifier the value is quite large but in full wave rectifier too the value of rectifier is significantly large.

Thus, in such types of arrangement we need smoothing circuit in order to remove these ripples. These ripples are the AC components in the DC voltage. This is called pulsating DC voltage. If this pulsating DC voltage is used in several applications it lead to poor performance of the device. Thus, the Smoothing circuit is used, filter works as a smoothing circuit for rectifier system.

Polyphase rectifiers

But after this smoothing process the rectifier voltage falls to zero at some point. Therefore, if in place of single phase transformer we use three phase transformer the ripple factor can be reduced up to a large extent.

Know about Three Phase Rectifier in Hindi. Three Phase Bridge Rectifier Working in Hindi

One of the significant advantage of three phase transformer is that the rectified voltage do not falls to zero even when no smoothing arrangement is used. In three phase half wave rectifier, three diodes are connected to each of the three phase of secondary winding of the transformer.

3 phase rectifier working

The three phases of secondary are connected in the form of star thus it is also called Star Connected Secondary. The anode terminal of the diode is connected to the secondary winding of the transformer.

And the three phases of the transformer is connected together at a common point called neutral. This neutral point provides the negative terminal to the load and is earthed.

Each diodes conducts for one third of the AC cycle and remaining two diodes will remains open circuit. The ouput DC voltage will be between the peak value of supply voltage and half of the supply voltage. It is evident from the above calculations that the ripple factor for the 3 phase half wave rectifier is 0. In single phase half have rectifier the value of ripple factor is 1.

3 phase rectifier working

Thus, it is evident that the value of ripple factor in 3 phase rectifier is very less in comparison to single phase rectifier. Moreover, the frequency of the ripples in three phase rectifier is very high. Thus, due to this these ripples can be easily filtered. The ripple frequency in case of three phase rectifiers is three times of the supply frequency.


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