Series Connect Lab SM Power Supplies

[The Great Attractor]

Larry Underwood wrote:

I need a variable bench supply that will provide 0-32VDC at 30A. I
already have two of these inexpensive (0-16VDC 30A) units.

[...]

Once in the university, there was a need for a 100KV supply. There were
25KV supplies with both terminals isolated from ground. Professor
connected four of these in series without any doubt in mind ))
True story, I omit the names


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

HVDC supplies will almost certainly, always be fully isolated. Any
grounded element is by customer option or deliberate action.
And it will NOT always be the negative node.

I have three HV bench supplies. All have the BNC-type HV connectors,
with one side grounded.

John

You might want to look into that. Look closer.

 

[TheGlimmerMan]

If he was that smart,

Smarter than ANY of you retard bandwagon dolts.

he's have a job

You lacks an education.

and be so busy he wouldn't have
time to go online.

I can work 12 hour days, and still come home to pile it on to a
retarded twit like you. You deserve less.

 

[Martin Riddle]

"The Great Attractor"

On Mon, 24 Oct 2011 08:55:30 -0500, Vladimir Vassilevsky



Larry Underwood wrote:

I need a variable bench supply that will provide 0-32VDC at 30A. I
already have two of these inexpensive (0-16VDC 30A) units.

[...]

Once in the university, there was a need for a 100KV supply. There
were
25KV supplies with both terminals isolated from ground. Professor
connected four of these in series without any doubt in mind ))
True story, I omit the names


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

HVDC supplies will almost certainly, always be fully isolated. Any
grounded element is by customer option or deliberate action.
And it will NOT always be the negative node.

I have three HV bench supplies. All have the BNC-type HV connectors,
with one side grounded.

John

You might want to look into that. Look closer.

They sound like Bertan supplies. I think they offer some isolation.
Are they 6kv supplies? BNC connectors with a 3" phenolic insert?

Cheers

 

[[email protected]]

0.15V x 5. (in series) (which would not work for this application to
begin with).

Interesting. .15V X 5 = .35V in AlwaysWrong land. Now that we have your
arithmetic aptitude nailed down...

Are you saying that they drop three quarters of a volt each?

No, I'm saying that you're *ALWAYS* wrong, AlwaysWrong.

You are an idiot.

I'm not the one who believes that .15V * 5 = .35V, AlwaysWrong.

They need to be in parallel and they need to all be thermally bonded to
each other, which still may not work.
Irrelevant.

**** off and die, Williams, you stupid putz!

Isn't it soooo cute when AlwaysWrong calls people stupid?

 

[John S]

Interesting. .15V X 5 = .35V in AlwaysWrong land. Now that we have your
arithmetic aptitude nailed down...

It was nailed down back when we saw he couldn't calculate the flight
time of light between planets. This is just confirmation of his lack of
aptitude.

 

[josephkk]

If he was that smart, he's have a job and be so busy he wouldn't have
time to go online.

Maybe not with a personality as offensive as shown here. Think about how
it would go in an interview.

?-)

 

[Martin Riddle]

On Mon, 24 Oct 2011 07:19:43 -0700, The Great Attractor

On Mon, 24 Oct 2011 08:55:30 -0500, Vladimir Vassilevsky



Larry Underwood wrote:

I need a variable bench supply that will provide 0-32VDC at 30A.
I
already have two of these inexpensive (0-16VDC 30A) units.

[...]

Once in the university, there was a need for a 100KV supply. There
were
25KV supplies with both terminals isolated from ground. Professor
connected four of these in series without any doubt in mind ))
True story, I omit the names


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

HVDC supplies will almost certainly, always be fully isolated.
Any
grounded element is by customer option or deliberate action.
And it will NOT always be the negative node.

I have three HV bench supplies. All have the BNC-type HV connectors,
with one side grounded.

John

You might want to look into that. Look closer.

ftp://jjlarkin.lmi.net/Bertan_HV.JPG

The connector barrel is zero ohms to the chassis.

You are AlwaysWrong.

John

That’s an old one, before they moved to hicksville.

Cheers

 

[Mark Datter]

Before or after the HR people take a baseball bat to his skull?

His jaw must be hurting him lately. Boo hoo!

That is a sign, Terrell, of your approaching decrepitude.

Wallow in it the short while it lasts, asswipe. I hope the lingering
pain gets worse and worse.

 

[TheGlimmerMan]

Interesting. .15V X 5 = .35V in AlwaysWrong land. Now that we have your
arithmetic aptitude nailed down...

All I did was look at and copy what he wrote, moving the decimal. I
did no calculations.

Not even a guesstimate. I would have seen it easily, but itwasn't
worth my time, sort of like you. So like I said... All I did was rinse
and repeat (move the decimal), thinking that was his mistake.

Sorry, but you dolts are "wrong again".
Let alone the fact that it isn't 0.15 V either. Funny that none of you
'noticed' that.

 

[MrTallyman]

He said "series."

John

And you think they are going to drop nearly 3/4 of a volt each?

 

[DonMack]

PSU's can be connected in series only if the grounds are isolated. That is,
the Negative of each supply has to be floating. Else what happens, if a
negative is grounded and you connect the positive of one supply to the
negative(ground) of the other you are directly shorting that positive
terminal to ground. It will behave exactly as if you simply shorted the +
to - on a single PSU. It will either burn up or trigger some over current
protection.

For non-load required supplies:
One simple way to check this is to connect them in series as usual but
insert a larger resistance(e.g., 1k 10W) inbetween the + of one supply and
the - of the next. Do not load the final supply. If they are floating there
will be no voltage drop across the resistor. Reducing the resistance should,
theoretically not matter and setting it to 0 should get you where you want.

GND--[-PSU+]--R--[-PSU+]

But if the PSU's are internally grounded you'll actually end up with this

GND--[-PSU+]--R--GND--[-PSU+]

in the first case no current will flow through R and the second case there
will be.




For loaded supplies:
In this case you will have to use a low enough resistance(and high enough W)
to load each supplies

GND--[-PSU+]--nR--[-PSU+]--R--GND

But if the PSU's are internally grounded you'll actually end up with this

GND--[-PSU+]--nR--GND--[-PSU+]--R--GND

If the PSU voltage is V, for example, then you have V---nR---V---R---GND for
the first

which results in 2V/(n + 1)R current flowing through the resistors which
gives the voltage n/(n+1)*2V across the nR resistor.

In the second you have

V---nR---GND

which gives a voltage of V across the nR resistor.

By choosing n < 1(preferably << 1) you'll end up with a different voltage.

i.e.,

Use significantly different resistors. If the PSU's are isolated then the
voltage across the first resistor will be different than V.

It's really not that much more complicated than the first method and this
method works for both cases.
------------

The whole point of using resistors is to prevent shorting and possibly
supply a load to the supply. We can determine the behavior of the PSU's
simply by measuring the voltage across the resistors. It's a quick method,
fairly accurate, and relatively non-destructive if done with a bit of common
sense(e.g., choosing R appropriately).

As others have mentioned you'll still have to deal with the maximum current
issue as each supply will have to handle the maximum current you are putting
into the load. Also diodes are generally put across the outputs to prevent
startup issues.

 

[Tom Del Rosso]

Maybe he is really, really smart and just pretends to be AlwaysWrong.

Since Skybuck appears to be even less intelligent but less anti-social, and
meds can do that, I suspect he is Skybuck off the meds.

Now he's going to say I'm clearly wrong because of the time of the posts,
but I can't even see most of them.

 

[Spehro Pefhany]

I didn't say, but a silicon PN diode could drop that, or more, at 30
amps.

John

More like a volt for a 6A rectifier at that current.


Best regards,
Spehro Pefhany

 

[[email protected]]

More like a volt for a 6A rectifier at that current.

At 30A? ;-)

 

[Spehro Pefhany]

At 30A? ;-)

I didn't say it would do it for very _long_.. ;-)


Best regards,
Spehro Pefhany

 

[TheGlimmerMan]

Why does that not surprise us?

John

Because you are a presumptuous twit.

 

[MrTallyman]

Since Skybuck appears to be even less intelligent but less anti-social, and
meds can do that, I suspect he is Skybuck off the meds.

Now he's going to say I'm clearly wrong because of the time of the posts,
but I can't even see most of them.

No, you are clearly nothing more than a complete and utter Usenet
retard. It has nothing to do with the time of the posts, you stupid
ditz.

 

[MrTallyman]

More like a volt for a 6A rectifier at that current.


Best regards,
Spehro Pefhany

A "6A rectifier" at 30 Amps would be a small explosion, and that's about
it.

 

[Spehro Pefhany]

A "6A rectifier" at 30 Amps would be a small explosion, and that's about
it.

Nah, for a second or more it would be well within specifications. Then
it would overheat if the current continued.


Best regards,
Spehro Pefhany

 

[John S]

Strange claim.

Dont forget that some power diodes drop upto 1.5v each at full
current, 0.6v is only the knee voltage.


NT

How could he forget? He never knew to begin with.