charge 100mF bulk capacitor

Let's repeat your application to see if we can understand your application ok.

The capacitor of 100mF is at the output of PFC, right? But what is the connection between your PFC output and the load? Your PFC has a plug of 10Amp and 220Vac, right? But how it is related to 30kW - is it your load level? Where the 30kW is connected?

Is it possible to attach a simple diagram to show your application?

hi

yes the 100mF is at the output of pfc

directly connected to the load, but the during charge time the converter is not working

well the load of the system is an x-ray tube, this meas that the 30 kW is at lest charged for 100ms and after stop for a time related to the cooling curve of the anodeso the bulk capacitor are for energy storage and in between one shot to another can elapse 10 seconds or more

best regards

well the system can be divided in this way

1) ac-dc input stage

2) bulk storage capacitors

3) H bridge converter

4) High voltage transformer

5) rectifier and measure system

6) x-ray tube

because the load is a power load but for short time

we need a energy storage to have istantaneous high peak power output

to supply the load and after wait to recharge the energy storage

the storage is better to be capacitive instead to be battery one because of the

fast distarge due to the load

regards

massimo

From my previous experience how to start up with charging big-value capacitors, it looks there are several options. For example, the listed two options can be your reference:

* Option 1: adding a resistor in series connection with the pre-start diode and adding a relay or a solid switch across the added resistor. At initial start, the relay is open, the resistor will limit the charging current. After charging time, the relay is closed. The relay / solid switch may be optional if the design can be made sure no current flowing through the resistor after charging complete.

* Option 2: adding a chopper in seriese connection with the pre-start didoe and control the chopper to limit the charging current.

Option 1 is simple. Option 2 can save the energy dissipated in the current limit  resistor but more costy, also option 2 can make predefined charging rate if needed.

thaNks All for suggestion

well the precharging using resistor is well know and is what i use now.

what i would like toi know is,

becauise of i had to add a pfc to my system,

my project will have something more than the other if instead

to load the bulk capacitor using a resistor or a current limit system such as pre gegualtor or thyristor bridge,

use the pfc to smootlty loads the capacitors, is this possible? or has some one experience?

hi max

thaNks All for suggestion

well the precharging using resistor is well know and is what i use now.

what i would like toi know is,

becauise of i had to add a pfc to my system,

my project will have something more than the other if instead

to load the bulk capacitor using a resistor or a current limit system such as pre gegualtor or thyristor bridge,

use the pfc to smootlty loads the capacitors, is this possible? or has some one experience?

hi max

Hi Massimo,

I had similar project to do.  My choice was CCM average current PFC driver to drive Sepic converter. Sepic does not have problem with inrush current and excellent separation load / power source. Also easy to control EMI. Charging algorithm for capacity is "Constant Current" than "Constant Power" and on the end "Constant Voltage". In your application ,I 'm guessing ,  "Constant Current" will be 4-5A and" Constant Power" about 400W . Charing time  (if you charging  cap from 0V) will be about 20 sec.

Bona fortuna,

Dragan

Hi Dragan,

thanks for suggestion, if I well understand Your progetc is a PFC that's drive a sepic converter that's will charge the capacitors, is it rigth?

regards

Massimo

Hi Dragan,

So You'are using a pfc controller to drive a sepic instead to drive a traditional boost, is it right? what kind of controller do You suggest?

regards

massimo

Hi Massimo,

Yes, and I used IR1150 but  you can use any CCM controller. This is picture of schematic and I hope you figure out how to make interface boost driver to  Sepic converter .This schematic gives me 250W  @  universal input . Coil are separate and to reduce switching loss D6 is SiC-diode.Efficiency is about 94%..

If you need more details let me now:

Dragan

 ( dragan@dpipower.com )

Hi Dragan

thanks

massimo