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Aharon
Active Contributor

Join Date: Jan 2009
Posts: 20

LT3751 Charge Controller

02/17/2010 6:18 AM

Hi Guys

I need to charge 12000Uf bulk capacitors 0à 370V within 4 sec

I am going to use LT3751 Charger Controller for that.

Does someone have good experience with this Charger Controller

And can let some tips for good design?
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Electronic Wiz
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Join Date: Dec 2008
Location: Western Colorado, USA
Posts: 202
Good Answers: 16
#1

Re: LT3751 Charge Controller

02/17/2010 11:14 PM

That's a lot of capacitance to charge up to 370 volts in 4 seconds. The best place to go for advice on this controller is to Linear Tech itself, find their office nearest to you and talk to an applications engineer, if they don't know, they will find out for you if this will work.
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Aharon
Active Contributor

Join Date: Jan 2009
Posts: 20
#2
In reply to #1

Re: LT3751 Charge Controller

02/18/2010 4:37 AM

Thanks.

Well ,this is the worse case but most of the time it will be ~90V >>>> 370V

Any way I will take your suggestion and try Linear Tech itself.
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marcot
Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1372
Good Answers: 80
#3

Re: LT3751 Charge Controller

02/18/2010 8:12 AM

What is the voltage source available and its current limit?

If you have a 480Vac supply, it is easy. You just need a resistor (impulse rated) and a contactor.

240Vac voltages will require the addition of an inductor to semi-resonate the current to reach th 370Vdc.

How critical is the final value? Is 360-380V OK?

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Aharon
Active Contributor

Join Date: Jan 2009
Posts: 20
#4
In reply to #3

Re: LT3751 Charge Controller

02/18/2010 8:22 AM

Hi marcot

The accuracy is critical as you know E = 1/2CV^2.

The input is 12-15V an LTC3751 is a flay-back controller so

We are talking on DC/DC .

input: 12V-15V

Output: 90V – 370v
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marcot
Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1372
Good Answers: 80
#5
In reply to #4

Re: LT3751 Charge Controller

02/18/2010 6:40 PM

The power switch and diode(s) will need to be rated for about 800V for a reliable operation. 600V might work for a while though.

The problem you will face is with the discharge resistors. You must ensure that the bank is discharged to a safe level within 10 minutes and provide warnings labels. This discharge current can be a large part of your load. We use about 10Kohms 25W ceramic resistors in our product.

Also, the capacitor bank and busbars must be protected by an enclosure as a short circuit will result in an explosion and splattering of molten copper that can injure someone. This is a lot of energy that can discharge quickly and produces thousands of amps. This can make wires fly apart and whip you hard. Wear safety glasses (minimum protection) at all time. Read a few articles about arc flash protection.

Your voltage feedback must flow through many resistors supported by a suitable substrate to minimize the chance of a failure feeding 370V at high energy into your control circuit.

If your application is for rapid discharge, your capacitors will need to be selected accordingly. Many electrolytic capacitors will fail after a few rapid discharge cycles.

Good luck and play safe.

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