Paralleling of Bridge Rectifiers

[gadfly56]

You don't see something odd there ATSman?

I think you're conflating two conversations. drcambell linked to a part that sells for $6.57 and ATSman came back with a part that sells for $12.99. A bit of drollery in a side conversation.

On the main issue, ATSman is looking for a real alternative to a $299 part. I was able to find it for $260. What a bargain! At the supplier's web site, that particular item is OEM and they don't release the specs. There's no way to tell whether the e-bay alternative might actually work. Or at least I couldn't.

 

[iwire]

I think you're conflating two conversations. drcambell linked to a part that sells for $6.57 and ATSman came back with a part that sells for $12.99. A bit of drollery in a side conversation.

No, I got that fine.

What I think is odd is that he wants to find a cheaper part for a mission critical device.

Personally I would stick with factory parts and we have not even touched on the listing issues using different parts inside listed equipment.

 

[gadfly56]

No, I got that fine.

What I think is odd is that he wants to find a cheaper part for a mission critical device.

Personally I would stick with factory parts and we have not even touched on the listing issues using different parts inside listed equipment.

OK, I see your point. I assumed he'd be looking for something listed, but if that's unique to the manufacturer he may get no relief.

 

[iwire]

I moved the side discussion to its own thread, please join it here


EDIT:


Sorry, it posted the wrong link, here is the correct one.



http://forums.mikeholt.com/showthread.php?t=180957

 

[ATSman]

And The Plot Thickens

And The Plot Thickens

Check this out.
This is an older version of the rectifier module that uses 4 br rectifiers.
The wiring shows they use only 2 diodes in each bridge to form the dual rectifier
in the sketch. I think they do this to double the Repetitive Peak Reverse Voltage (VRRM)
Maybe something their engr dept thought was more critical than the rectifiers current rating
with regard to failures which can cause nasty blowups when the coil shorts out. Not sure.
The JH911 module is proprietary but I did get the spec sheet and the VRRM is 4,000V which is
unusually high and may explain the higher price per module.
And no, I will not install a substitute module other than the OEM part#. Not worth the liability.
But it is good to know that in an emergency I could build the older version with parts I have on hand
if the ATS is down and delivery time is of the essence.

 

[FionaZuppa]

Check this out.
This is an older version of the rectifier module that uses 4 br rectifiers.
The wiring shows they use only 2 diodes in each bridge to form the dual rectifier
in the sketch. I think they do this to double the Repetitive Peak Reverse Voltage (VRRM)
Maybe something their engr dept thought was more critical than the rectifiers current rating
with regard to failures which can cause nasty blowups when the coil shorts out. Not sure.
The JH911 module is proprietary but I did get the spec sheet and the VRRM is 4,000V which is
unusually high and may explain the higher price per module.
And no, I will not install a substitute module other than the OEM part#. Not worth the liability.
But it is good to know that in an emergency I could build the older version with parts I have on hand
if the ATS is down and delivery time is of the essence.

2x PIV means 2x fwd voltage drop too per pair, thats 4x one diode for rectification.

 

[GoldDigger]

2x PIV means 2x fwd voltage drop too per pair, thats 4x one diode for rectification.

All the more reason to use controlled FETs or other similar more sophisticated devices to build really critical bridges.

 

[gar]

161219-2424 EST

A small sample of diode data. 1N4148 max is 400 mA.

D1 1N4148
D2 1N4148 same bag as D1
D3 1N4148 different source, after thought to find a different batch
D4 1N4005

D1 to D2 looks strange 40 to 100 mA.

mA ----- Volts

------------ D1 ------ D2 ------ D4 ----- D3

_10 ----- 0.728 --- 0.723 --- 0.701
_20 ----- 0.768 --- 0.763 --- 0.730
_40 ----- 0.812 --- 0.809 --- 0.757
100 ----- 0.877 --- 0.883 --- 0.784
200 ----- 0.947 --- 0.960 --- 0.798 --- 0.904

D1 vs D3 shows a considerable difference.

D4 to others is expected. Considerably higher current rating.

.

 

[GoldDigger]

A lab I worked in bought about 200 hand matched diode quads from HP to build ultrafast signal gates (looking a lot like diode bridges)
The summer intern opened all of the envelopes​ and dumped them into a drawer marked "matched quads"

Sent from my XT1585 using Tapatalk

 

[topgone]

A lab I worked in bought about 200 hand matched diode quads from HP to build ultrafast signal gates (looking a lot like diode bridges)
The summer intern opened all of the envelopes​ and dumped them into a drawer marked "matched quads"

Sent from my XT1585 using Tapatalk

They're no longer matched then?:lol::lol::lol:

 

[GoldDigger]

They're no longer matched then?

Some of them did of course. You just had to test them all to find them.
:angel:

Sent from my XT1585 using Tapatalk

 

[iwire]

The other, other topic. http://forums.mikeholt.com/showthread.php?t=180958

 

[gar]

161220-0952 EST

The use of a full wave bridge circuit reduces the PIV rating of the individual diodes by a factor of 2 compared to either a half wave rectifier with energy storage or a full wave center tapped rectifier. Draw each circuit and study it.

The so called paralleling of bridge modules as shown in this thread does not increase the PIV rating.

.

 

[Besoeker]

161220-0952 EST

The use of a full wave bridge circuit reduces the PIV rating of the individual diodes by a factor of 2 compared to either a half wave rectifier with energy storage or a full wave center tapped rectifier. Draw each circuit and study it.

The so called paralleling of bridge modules as shown in this thread does not increase the PIV rating.

.

And debatable what it does for increasing the total current capacity.

 

[Jraef]

Bridge rectifiers are run in parallel all the time for 12 and 18 pulse drive inputs to reduce harmonics.



In an 18 pulse drive like this, the rectifier diodes in each parallel bridge are rated at 1/3 the size of those in a single (6 pulse) rectifier (rounded up to the nearest standard size). The purpose of running parallel bridges is not to decrease the size of course, but the net effect is the same.

 

[Jraef]

161220-0952 EST

The use of a full wave bridge circuit reduces the PIV rating of the individual diodes by a factor of 2 compared to either a half wave rectifier with energy storage or a full wave center tapped rectifier. Draw each circuit and study it.

The so called paralleling of bridge modules as shown in this thread does not increase the PIV rating.

.

Correct. PIV ratings are increased by running thyristors in series, not parallel.

 

[Besoeker]

Bridge rectifiers are run in parallel all the time for 12 and 18 pulse drive inputs to reduce harmonics.

View attachment 16328

In an 18 pulse drive like this, the rectifier diodes in each parallel bridge are rated at 1/3 the size of those in a single (6 pulse) rectifier (rounded up to the nearest standard size). The purpose of running parallel bridges is not to decrease the size of course, but the net effect is the same.

That's not really parallel though. The reduction in harmonics is because the conduction period commences at a different point in time for each device.

 

[ATSman]

New Quad Specs

New Quad Specs

These are the specs on the new quad module shown earlier
in this thread. Notice the high peak reverse voltage rating
which is critical to this application

 

[Besoeker]

Bridge rectifiers are run in parallel all the time for 12 and 18 pulse drive inputs to reduce harmonics.

View attachment 16328

In an 18 pulse drive like this, the rectifier diodes in each parallel bridge are rated at 1/3 the size of those in a single (6 pulse) rectifier (rounded up to the nearest standard size). The purpose of running parallel bridges is not to decrease the size of course, but the net effect is the same.

Aren't the bridges in series with positive of one connected to the negative of the next one up?

 

[GoldDigger]

Aren't the bridges in series with positive of one connected to the negative of the next one up?

It sure looks that way.
This 18 pulse bridge depends on adding the absolute values of all three winding sets at once to get the waveform that is to be filtered at the capacitor.
So the cap voltage is higher than the peak value of any one winding.
I had not given any thought on how to assemble an 18 pulse supply. I imagine that the parallel configuration would work too but has disadvantages compared to the serial form.
Each bridge contains diodes that are exposed to the peak value of its own windings' AC, but never the full bus DC.