# What are the names of these voltages for a 3-ph full-wave controlled rectifier?

1. ## What are the names of these voltages for a 3-ph full-wave controlled rectifier?

I ran through this chapter and reached this circuit which is fine and I solved the previous controlled 1-ph circuits' examples and I understand the parameters of the different voltages, current, power factor ... etc.

But when I reached the 3-ph controlled circuit with resistive load, I found different voltages that I couldn't find a source that explain them all. But I understand the rest of the measuring parameters.

This is the circuit: This is the solution of the example: I want to know what are the naming & difference between VL(m), Vphase & Vm?  Reply With Quote

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2. ## Re: What are the names of these voltages for a 3-ph full-wave controlled rectifier?

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3. ## Re: What are the names of these voltages for a 3-ph full-wave controlled rectifier?  Reply With Quote

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4. ## Re: What are the names of these voltages for a 3-ph full-wave controlled rectifier?

its been a while since i did power, so i;m a little rusty:

the coils are a transformer - provides isolation and step up or step down depending on turns ratios
as in single phase

the source on the left is a delta - that is, the three phases are 120 degrees part and the ends
of the three coils (1 per phase) are connected to look like an equilateral triangle
here is is drawn as a series connection that ends at the start
the voltages are line to line, or just line as they appear in the equations

the secondary is a y - usually drawn as an equilateral y
as in the drawing, the end of the coils tied together are called the neutral
the other ends are the phase voltages, a, b and c as labeled

VL(m) would be the maximum line voltage -
Vphase the phase voltage
Vm the maximum (phase) voltage
Im is the maximum current
Vo(avg) is the average output voltage -
the cos(20) is there because the conduction angle, where you turn the thyristers on, is 20 degrees
(or is it the angle the thyrister is on?)

Io(avg) is the average output current
Ith(m) is the maximum current in a thyrister
Ith(aveg) s the average currnt in a thyrister - they each conduct 1/3 of the time

part of this however seems off, as one needs a + thyrister (1, 3, 5) and a - thyrister (4, 6, 2) on at the same time to conduct
and they have to turn on in the correct sequence
1 and 4 (for example) cannot be on at the same time
1 and 6 are on for 1/2 the conduction time of 1 and 1 and 2 are on for the other 1/2 of the conduction time of 1

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5. ## Re: What are the names of these voltages for a 3-ph full-wave controlled rectifier? Originally Posted by wwfeldman its been a while since i did power, so i;m a little rusty:
what you think is rusty is gold to me :)

the coils are a transformer - provides isolation and step up or step down depending on turns ratios
as in single phase
yep i know transformer stuff ..

the source on the left is a delta - that is, the three phases are 120 degrees part and the ends
of the three coils (1 per phase) are connected to look like an equilateral triangle
here is is drawn as a series connection that ends at the start
the voltages are line to line, or just line as they appear in the equations
the secondary is a y - usually drawn as an equilateral y
as in the drawing, the end of the coils tied together are called the neutral
the other ends are the phase voltages, a, b and c as labeled
yeah this is the configuration that step the voltages from delta to star + having the neutral wire for the star connection and with the unneeded neutral for the primary delta is brilliant thing I just thought about .. because it's not important for primary delta connection because it doesn't need to connect to a load and it's actually going to star connection with isolation property. and as the star is beneficially having the neutral wire, then with proper electrical installation, if this neutral is grounded, then that would be wonderful as what happened to my apartment electrical issues i had recently and posted a thread here about it :)

VL(m) would be the maximum line voltage -
Vphase the phase voltage
Vm the maximum (phase) voltage
thank you so much that's what i needed to know

the cos(20) is there because the conduction angle, where you turn the thyristers on, is 20 degrees
(or is it the angle the thyrister is on?)
yep .. there's a conduction angle it's the controlled rectifier chapter.

Im is the maximum current
Vo(avg) is the average output voltage -
Io(avg) is the average output current
Ith(m) is the maximum current in a thyrister
Ith(aveg) s the average currnt in a thyrister - they each conduct 1/3 of the time
thanks again .. extra important information, thank you so much for the rich answer :)

part of this however seems off, as one needs a + thyrister (1, 3, 5) and a - thyrister (4, 6, 2) on at the same time to conduct
yep, it's a book for electronics diploma program, it's not so specialized and dealing with the engineering details and analysis. it's just to teach the important topics in power electronics.

and they have to turn on in the correct sequence
1 and 4 (for example) cannot be on at the same time
1 and 6 are on for 1/2 the conduction time of 1 and 1 and 2 are on for the other 1/2 of the conduction time of 1
yeah I think this process is explained in the book but i haven't emphasized on it because i just have to solve this example with knowing those parameters.  Reply With Quote

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