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What Is Double Star With IPT Rectifier Circuit?

May 31, 2020

1. Overview:

Balance reactor: An iron core coil with a center tap has the same number of turns on both sides of the tap and the same inductance. When an alternating current flows through the coil on either side, there will be induced electromotive force with same value and the same direction on both sides.

Double reverse star transformer: The rectifier transformer has two sets of secondary windings, both are connected into  star, but the two windings are connected oppositely to the thyristors, so the star is opposite. 

2. Circit Diagram:


3. The role of balancing reactors: 

The rectifier with double star with balanced reactor circuit reduces the current waveform factor of flowing through the thyristors and transformer secondary. When output the same DC current, the rated current of the diodes or thyristors can be reduced and improve the utilization rate of the transformer, when the output is high current, the quantity of parallel of thyristors could be reduced or no need to be connected in parallel.  

4. Working principle:

(1) Resistive load:

α≤60oTime,The waveform is continuous,

formula 1

α〉60oTime,The waveform is intermittent,

formula 2

The α phase shift range is 120o

waveform 3 

Resistive load waveform of double reverse star controllable rectifier circuit with balanced reactor (when α = 30o, α = 60o)

(2) Inductive load:

l α≤60oTime,there is no negative voltage in the waveform, the same resistance load.

formula 3

l 60o<α<90o time, a negative voltage appears in the waveform.

formula 4

l α=90oTime, Ud≈0


Double star with balanced reactor thyristor rectifier circuit inductive load α = 90o waveform

5. Features of double star rectifier with IPT(interface transformer) circuit

(1) The double reverse star circuit is a parallel connection of two sets of three-phase half-wave rectification circuits. The output rectified voltage waveform is the same as that of six-phase half-wave rectification, so the pulsation is much smaller than that of three-phase half-wave rectification.

(2) Since there are two phases conducting at the same time, the magnetic circuit of the rectifier transformer is balanced. Unlike three-phase half-wave rectification, there is the problem of DC magnetization.

(3) Compared with the six-phase half-wave rectification, the utilization rate of the secondary winding of the rectifier transformer is doubled, so when the same DC current is output, the capacity of the transformer is smaller than that of the six-phase half-wave rectification.

(4) Each rectifier element bears half of the load current, and the conduction time is doubled compared with three-phase half-wave rectification, which improves the capacity of the rectifier element to withstand the load. 

If any questions about rectifier, call us: 

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