Phase Controlled Rectifier-2 Study notes For Electrical Engineering

By Yash Bansal|Updated : June 13th, 2021

In this article, you will find the study notes on Phase Control Rectifier-2 which will cover the topics such as Three-Phase Rectifier, Three-Phase Diode Rectifier, Three Phase Half Controlled Rectifier & 3- phase Full Controlled Rectifier .

In this article, you will find the study notes on Phase Control Rectifier-2 which will cover the topics such as Three-Phase Rectifier, Three-Phase Diode Rectifier, Three Phase Half Controlled Rectifier & 3- phase Full Controlled Rectifier .

 

Three-Phase Rectifier

As the application Point of view Three-phase controlled rectifiers have a wide range of applications, from small rectifiers to large High Voltage Direct Current (HVDC) transmission systems. They are used for electro-chemical process, many kinds of motor drives, traction equipment, controlled power supplies, and many other applications.

From the point of view of the commutation process, they can be classified in two important categories: Line Commutated Controlled Rectifiers (Thyristor Rectifiers), and Force Commutated PWM Rectifiers.

  • The 3-Phase Controlled rectifier provide a maximum dc output of "Vdc(max)=2Vm/∏" the output ripple frequency is equal to the twice the ac supply frequency.

Three-Phase Diode Rectifier

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The circuit shown in the given figure by using 6 diodes Named as three phase Rectifier. It shows the AC side currents and DC side voltage for the case of high load inductance.

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we see that on the AC side, the RMS current, Is will be

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while the fundamental current, i.e. the current at power frequency is:

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Again, inductance on the AC side will delay commutation, causing a voltage loss, i.e. the DC voltage will be less than that predicted by equation Vdo.

Waveforms of a three-phase full-wave rectifier with diodes and inductive load

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Three Phase Half Controlled Rectifier

 In the given figure below shows the circuit diagram of three phase half controlled converter supplying an R-L-E load. In the continuous conduction mode only one thyristor from top group and only one diode from the bottom group conduct at a time. However, unlike fully controlled converter here both devices from the same phase leg can conduct at the same time. Hence, there are nine conducting modes as shown in Figure.

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3- Phase Full Controlled Rectifier

In 3-phase full controlled rectifier 6 thyristors are needed to accommodate three phases. In the given figure below shows the schematic of the system, and Figureshows the output voltage waveforms.

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Output Waveform for 3-Phase Full Controlled Rectifier

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  • The delay angle α is again measured from the point that a thyristor becomes forward biased, but in this case the point is at the intersection of the voltage waveforms of two different phases. The voltage on the DC side is then (the subscript o here again meaning Ls = 0).

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which leads to

Is1 = 0.78 Id

and the relationship between Vdo and V

V = Vdo Cos(α)

  • Again, if the delay angle α is extended beyond 90º,the converter transfers power from the DC side to the AC side, becoming an inverter. We should keep in mind, though that even in this case the converter is drawing reactive power from the AC side.
  • For both 1-phase and 3-phase controlled rectifiers, a delay in α creates a phase displacement of the phase current with respect to the phase voltage, equal to α. The cosine of this angle is the power factor of the fundamental harmonic.

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