high voltage capacitor charger - how to

[nescafe]

Hi.

I want to charge my capacitor bank with 72V-20A DC source.

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

DC source is constant so capacitors can be "recharged" all the time.
The capacitor bank should be made of 450V / 400uF capacitors and normal
power consumption of our electronics is around 800 - 900W.

Does anyone has some DIY project on this or maybe some guide how to start ?

Regards !

 

[nescafe]

btw 100000uf of stronger can also be used.


On 08/14/2012 08:53 AM, nescafe wrote:

Hi.

I want to charge my capacitor bank with 72V-20A DC source.

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

DC source is constant so capacitors can be "recharged" all the time.
The capacitor bank should be made of 450V / 400uF capacitors and normal
power consumption of our electronics is around 800 - 900W.

Does anyone has some DIY project on this or maybe some guide how to start ?

Regards !

 

[Uwe Hercksen]

nescafe schrieb:

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

Hello,

it is not possible to store 1 kW in a capacitor bank, even if it is a
very large one. But if you want to store 1 kWh this may be done, if
there are enough capacitors of a suitable capacity and voltage. The bank
might be much too large, heavy and expensive.

Bye

 

[Phil Hobbs]

nescafe wrote:

btw 100000uf of stronger can also be used.

On 08/14/2012 08:53 AM, nescafe wrote:
Hi.

I want to charge my capacitor bank with 72V-20A DC source.

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

DC source is constant so capacitors can be "recharged" all the time.
The capacitor bank should be made of 450V / 400uF capacitors and normal
power consumption of our electronics is around 800 - 900W.

Does anyone has some DIY project on this or maybe some guide how to start ?

Regards !

You've got lots of power available for the job, but the job itself
doesn't make much sense to me. First off, do you mean that you want to
draw 1 kW from the capacitors, or that you need enough capacitors to
filter your 1 kW switching supply?

Second, a 1 kW class switching supply is _not_ a beginner's project.
There's way too much that's bound to go expensively (and maybe
dangerously) wrong.

What are you actually trying to do?

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

 

[nescafe]

On 08/14/2012 12:20 PM, Uwe Hercksen wrote:

nescafe schrieb:

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

Hello,

it is not possible to store 1 kW in a capacitor bank, even if it is a
very large one. But if you want to store 1 kWh this may be done, if
there are enough capacitors of a suitable capacity and voltage. The bank
might be much too large, heavy and expensive.

Bye

-------------------------

First off, do you mean that you want to draw 1 kW from the capacitors ?
-yes that's what i want

The bank might be much too large, heavy and expensive
- i agree that this could be a problem.

But i do have some additional questions.
e.g. if i dismantle some 12/220 - 2kw - DC/AC converter and if i measure
voltage on exit capacitor i will get around 250V.
Ok.
If i want to use this 250V to run some 2kw application ( working on this
voltage ) everything works OK. I tested this.

So as far as i understand this i can make the same stuff but with 450V
capacitor and with less electronic. Maybe i dont need capacitor bank ?

 

On Tue, 14 Aug 2012 13:01:18 +0200, nescafe <nescafe@com.com> wrote:

On 08/14/2012 12:20 PM, Uwe Hercksen wrote:


nescafe schrieb:

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

Hello,

it is not possible to store 1 kW in a capacitor bank, even if it is a
very large one. But if you want to store 1 kWh this may be done, if
there are enough capacitors of a suitable capacity and voltage. The bank
might be much too large, heavy and expensive.

Bye

-------------------------
First off, do you mean that you want to draw 1 kW from the capacitors ?
-yes that's what i want

The bank might be much too large, heavy and expensive
- i agree that this could be a problem.

But i do have some additional questions.
e.g. if i dismantle some 12/220 - 2kw - DC/AC converter and if i measure
voltage on exit capacitor i will get around 250V.
Ok.
If i want to use this 250V to run some 2kw application ( working on this
voltage ) everything works OK. I tested this.

So as far as i understand this i can make the same stuff but with 450V
capacitor and with less electronic. Maybe i dont need capacitor bank ?


72VDC/20 amps is enough to support a 1KW load. The dc-dc converter

will output whatever voltage it is designed for. The capacitor is
just necessary for smoothing not to supply the raw power.

If you wanted reserve power for a prolonged period when the 72 volts
isn't present, then a battery makes sense, or a super cap if the
outage time is short. Then use that to store energy and convert it up
to 450 for the load.

 

[nescafe]

Can you tell us what you're trying to achieve,
*not* what you're thinking/doing.
-- to run one 450V circuit. This circuit is used as some kind of

controller and you can power it with 450VDC source.

To run properly the circuit needs minimum 300W.
---------------------

 

[Jasen Betts]

On 2012-08-14, nescafe <nescafe@com.com> wrote:

On 08/14/2012 12:20 PM, Uwe Hercksen wrote:


nescafe schrieb:

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

Hello,

it is not possible to store 1 kW in a capacitor bank, even if it is a
very large one. But if you want to store 1 kWh this may be done, if
there are enough capacitors of a suitable capacity and voltage. The bank
might be much too large, heavy and expensive.

Bye

-------------------------
First off, do you mean that you want to draw 1 kW from the capacitors ?
-yes that's what i want

The bank might be much too large, heavy and expensive
- i agree that this could be a problem.

But i do have some additional questions.
e.g. if i dismantle some 12/220 - 2kw - DC/AC converter and if i measure
voltage on exit capacitor i will get around 250V.
Ok.
If i want to use this 250V to run some 2kw application ( working on this
voltage ) everything works OK. I tested this.

So as far as i understand this i can make the same stuff but with 450V
capacitor and with less electronic. Maybe i dont need capacitor bank ?

If you can replace the rectifier on the main transformer of the 2KW
inverter with one that gives twice the voltage you'd be close to a
solution, you'd then need to mess with the feedback to reduce the
output voltage to 450V.

sounds dangerous and potentially expensive/exciting, especially if you don't
have a schematic and understanding of how the inverter is supposed to
work.

it might be better to put autotransformr on the inverter output to
step it up and rectify the result.

This is for what? A battery powered "toob" amp?

--
⚂⚃ 100% natural

 

[Phil Hobbs]

nescafe wrote:

Can you tell us what you're trying to achieve,
*not* what you're thinking/doing.
-- to run one 450V circuit. This circuit is used as some kind of
controller and you can power it with 450VDC source.

To run properly the circuit needs minimum 300W.
---------------------

A "capacitor charger" is a device that repetitively charges up a
capacitor bank, which is then discharged very fast to provide short
pulses of very high peak power, e.g. for a flashlamp, railgun or coin
shrinker. The design requirements for that job are quite different from
just filtering a high current 450V DC supply, which is what it sounds
like you're trying to do.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

 

[fungus]

On Tuesday, August 14, 2012 8:53:02 AM UTC+2, nescafe wrote:

Hi.



I want to charge my capacitor bank with 72V-20A DC source.



The idea is to store 1KW in this capacitor bank and then to use this

power to run some 450V electronics.



DC source is constant so capacitors can be "recharged" all the time.

The capacitor bank should be made of 450V / 400uF capacitors and normal

power consumption of our electronics is around 800 - 900W.

Can you tell us what you're trying to achieve,
*not* what you're thinking/doing.

eg.

I have a 72V-20A DC source, I want to use it
to power a 450V AC device.

I have the following components...


(This might be what you're trying to do, it's
not clear...)

 

[nescafe]

Are you trying to use a car battery inverter to step the voltage up to
450V?
- yes. I'v done this before and it worked.
There are of course few problems regarding this approach.
Safety would be on the first place, but if the you do this with some
basic/extra precaution then everything works ok.
And it's quite exciting
---------------------
Like Phil suggested if i go with capacitor bank i will not get what i
need and beside this i would spend bunch on money for nothing.
-------------------
What im doing
---------------------
I'v made electric car with reg. breaking.
Its using 3phase 11kw motor and the only thing that i need is stronger
DC/DC converter.
I dont have time to explain how all this works but to control the motor
i need 420 - 500V DC input.
DC /DC converter is connected to this motor control. Btw. 3 phase
approach is waaaay better then DC motor but as you can see there are
some problems. I can rewind motor or use some other controller or do
something else, but then again, that would not be me . To run the car
smoothly in first gear i need around 2,5kw ( first gear with fast start
and small hill ) afterwards normal consumption is much lower.
---------------------
Back to the problem ( and guys, please stay on this topic, we can talk
about EV later ).
---------------------
I firstly connected 2x 2KW AC/DC 12/220V converters ( galvanic separated
) and it worked OK
Then i was thinking, damn, there must be a way just to change the output
capacitor and rectifier ( like Jasen suggested ) to make this work. So
my next plan is to buy some 72V DC/AC inverter and to do just that.
Change the capacitor and rectifier part.
---------------------
Would this be possible to do ?

 

[fungus]

On Tuesday, August 14, 2012 1:54:17 PM UTC+2, nescafe wrote:

Can you tell us what you're trying to achieve,
*not* what you're thinking/doing.

-- to run one 450V circuit. This circuit is used as some kind of
controller and you can power it with 450VDC source.


To run properly the circuit needs minimum 300W.

OK, you've got 72V-20A DC source, that's
1440W - plenty of power but you need a
transformer.

Are you trying to use a car battery inverter
to step the voltage up to 450V?

 

[Fred Abse]

On Tue, 14 Aug 2012 08:53:02 +0200, nescafe wrote:

I want to charge my capacitor bank with 72V-20A DC source.

The idea is to store 1KW in this capacitor bank and then to use this power
to run some 450V electronics.

How do you propose getting 450V from 72? Some sort of series-parallel
switching?

DC source is constant so capacitors can be "recharged" all the time.

That would appear to preclude switching , as described above. Define "all
the time".

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[fungus]

On Tuesday, August 14, 2012 6:21:21 PM UTC+2, nescafe wrote:

Are you trying to use a car battery inverter to step the voltage up to

450V?

- yes. I'v done this before and it worked.

OK...but the inverter you've got multiplies
the voltage by 20.

That's three times too much - your 72V will
turn into 1440V.

You need a different inverter or a way
to divide the voltage.

Dividing the voltage is complicated.

I'v made electric car with reg. breaking.

Oh, now everybody knows the secret! Be careful
the oil companies don't find out where you live.