Parallel or not

[FionaZuppa]

Make sure the bridges are the same
same as 3 ph with 1 ph removed

can i ask how this is paralleling two bridges?

 

[Ingenieur]

can i ask how this is paralleling two bridges?

outputs in parallel
each carries ~1/2 the load

 

[FionaZuppa]

outputs in parallel
each carries ~1/2 the load

hmmm, not true, the current vector is not shared (paralleled) across the bridge pair at output. what you have done is made each bridge (4 physical diodes) into 2 logical diodes. perfectly legit this way because of variances in making of diodes. :thumbsup:

 

[Ingenieur]

hmmm, not true, the current vector is not shared (paralleled) across the bridge pair at output. what you have done is made each bridge (4 physical diodes) into 2 logical diodes. perfectly legit this way because of variances in making of diodes. :thumbsup:

what???
the ouputs are not in parallel?
and each doesn't conduct 1/2 cycle thereby delivering 1/2 the power?

lol

 

[gar]

161219-1957 EST

If one simply looks at either bridge, then it is seen that by the external wiring that two diodes within the bridge are paralleled.

.

 

[iwire]

161219-1957 EST

If one simply looks at either bridge, then it is seen that by the external wiring that two diodes within the bridge are paralleled.

.

Don't get sucked into the abyss, someone is having fun.

 

[FionaZuppa]

Don't get sucked into the abyss, someone is having fun.

there is no abyss, gar is correct.

also, the comment about half power per bridge is ok since the current vector leaves one bridge and returns on the other, they just aint parallel, thats all.
the comment about each only conducting a half cycle is also false. each bridge conducts for every 180 of the AC :thumbsup:, the amps leaves one and returns on the other for every 180 :thumbsup:

where do you find 1kV diodes for this job at hand? amps wont be the issue, finding 1kV rated might be??

 

[Ingenieur]

there is no abyss, gar is correct.

also, the comment about half power per bridge is ok since the current vector leaves one bridge and returns on the other, they just aint parallel, thats all.
the comment about each only conducting a half cycle is also false. each bridge conducts for every 180 of the AC :thumbsup:, the amps leaves one and returns on the other for every 180 :thumbsup:

if gar is correct you are incorrect?

The outputs are in parallel
180 deg (Pi) is 1/2 cycle, it's the same thing lol
1 cycle is 360 deg (2Pi)

 

[GoldDigger]

161219-1957 EST

If one simply looks at either bridge, then it is seen that by the external wiring that two diodes within the bridge are paralleled.

.

And the other two diodes of each four diode bridge never conduct at the same time as the first two.
It becomes a full wave rectifier with each "diode" consisting of two diodes in parallel.
In theory, if current splits equally, able to supply twice the current a single bridge wired as a full wave bridge.

 

[FionaZuppa]

Another thing to consider is PIV. At 480Vdc you'd need devices rated at 1600V.

why 1600V
isnt 1.5x peak a good buffer? a fast pulse on a coil is gonna give back a nasty flyback, so that needs to be handled properly either with some decent zeners to GND or hefty reverse diode across the load (coil). i like zener method because of the freewheel diode will allow.

if gar is correct you are incorrect?

The outputs are in parallel
180 deg (Pi) is 1/2 cycle, it's the same thing lol
1 cycle is 360 deg (2Pi)

your Pi is spot on, your understanding of how the amps are flowing is not. for any given 1/2 cycle, amps flow in one direction only, it leaves one bridge and returns on the other, thus i may infer that both bridges are conducting at the same time, all the time, regardless of what 1/2 cycle you look at (less the dropout region of diode, etc).

 

[Ingenieur]

why 1600V
isnt 1.5x peak a good buffer? a fast pulse on a coil is gonna give back a nasty flyback, so that needs to be handled properly either with some decent zeners to GND or hefty reverse diode across the load (coil). i like zener method because of the freewheel diode will allow.


your Pi is spot on, your understanding of how the amps are flowing is not. for any given 1/2 cycle, amps flow in one direction only, it leaves one bridge and returns on the other, thus i may infer that both bridges are conducting at the same time, all the time, regardless of what 1/2 cycle you look at (less the dropout region of diode, etc).

not my Pi
everyone's

surmise to your little hearts content
the diodes/bridges are operating in parallel

 

[FionaZuppa]

not my Pi
everyone's

surmise to your little hearts content
the diodes/bridges are operating in parallel

the bridges are not in parallel, they operate in series, sorry.

what you have is, each bridge has 2x two diodes paralleled to handle 2x the amps per diode pair, each half of the logical bridge is on two physical bridges. just take a pen and follow + to - (AC) from one side to other, when you get to other side flip the voltage over and then follow back + to - (AC)

 

[gar]

161219-2124 EST

Redraw the circuit of post #9 and you will see that you have a single bridge circuit with each segment of the redrawn circuit consisting of two diodes in parallel.

Thus, the the circuit has paralleled diodes. The paralleling of the diodes occurs within a diode bridge package. One bridge package provides only two segrments of the real bridge circuit.

.

 

[Ingenieur]

Both bridges supply power/current to the same conductor
sounds like parallel to me

the bridges are not in parallel, they operate in series, sorry.

what you have is, each bridge has 2x two diodes paralleled to handle 2x the amps per diode pair, each half of the logical bridge is on two physical bridges. just take a pen and follow + to - (AC) from one side to other, when you get to other side flip the voltage over and then follow back + to - (AC)

 

[FionaZuppa]

161219-2124 EST

Redraw the circuit of post #9 and you will see that you have a single bridge circuit with each segment of the redrawn circuit consisting of two diodes in parallel.

Thus, the the circuit has paralleled diodes. The paralleling of the diodes occurs within a diode bridge package. One bridge package provides only two segrments of the real bridge circuit.

.

correction
One bridge package provides only one of two segments of the real bridge circuit. as is, it takes two physical packages to complete the ckt.

 

[FionaZuppa]

Both bridges supply power/current to the same conductor
sounds like parallel to me

really? please show us a trace when bottom AC is + and top AC is -, lets see how both physical packages provide amps to the +DC terminal at the same time.

hint: one bridge is a current source, the other is a current sink.

 

[Ingenieur]

really? please show us a trace when bottom AC is + and top AC is -, lets see how both physical packages provide amps to the +DC terminal at the same time.

Show me how 180 deg (angular not temperatre) is not equal to Pi or 1/2 of a sinusoidal signal
as you stated before: not 1/2 cycle but 180'deg lol

 

[GoldDigger]

161219-2124 EST

Redraw the circuit of post #9 and you will see that you have a single bridge circuit with each segment of the redrawn circuit consisting of two diodes in parallel.

Thus, the the circuit has paralleled diodes. The paralleling of the diodes occurs within a diode bridge package. One bridge package provides only two segrments of the real bridge circuit.

.

And the paralleled diodes within each bridge assembly are much more likely to be matched in characteristics and temperature compared to diodes in separate bridge assemblies.
I see this as a very elegant way of effectively doubling the bridge capacity with less concern for diode characteristic mismatch!

Thank You gar.

 

[FionaZuppa]

And the paralleled diodes within each bridge assembly are much more likely to be matched in characteristics and temperature compared to diodes in separate bridge assemblies.
I see this as a very elegant way of effectively doubling the bridge capacity with less concern for diode characteristic mismatch!

Thank You gar.

this is the exact reason why two physical bridges are used in series, one phys bridge on each side of the load.

 

[FionaZuppa]

Show me how 180 deg (angular not temperatre) is not equal to Pi or 1/2 of a sinusoidal signal
as you stated before: not 1/2 cycle but 180'deg lol

180 is indeed half cycle. you dont understand how that schematic works, so here, just follow the arrows per half cycle. at no time, EVER, are both bridges being current sources to the DC+ bus !!! have i made this clear ?