3 Phase Rectifier (6 and 12 Pulse Reactifier)




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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.

Step 1: Components

  • Perf Board
  • Connectors
  • Diode (i used 1N4007)

The Datasheet is attached here

Step 2: Putting Them Together

Basic soldering is needed here. Just solder the circuit all together. This is simple enough and only basic skill level is required.

Step 3: 6 Pulse Rectifier

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.

Step 4: 12 Pulse 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. A twelve-pulse bridge consists of two six-pulse bridge circuits connected in series, with their AC connections fed from a supply transformer that produces a 30° phase shift between the two bridges. 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.



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    5 Discussions


    2 years ago

    i still dont understand about 12 pulse .. can u tell me about how to make those star and wye circuit ? and how do i find those components ?

    1 reply

    Reply 2 years ago

    wye (also called star) and delta ( also called triangle) are the coupling of the individual phases relative to one another. those are not components. you can't "make them".

    here is a good read: https://en.wikipedia.org/wiki/Three-phase_electric_power#Balanced_circuits


    Reply 2 years ago

    maybe, depends on what type of motor it is, but it most likely will only be two phase, low voltage, and low power. basically, all you will get is a signal, and a hardly useable one at that.

    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)


    3 years ago on Introduction

    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! Nice!