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problems.. keeps tripping the house power

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audio:deviant

Sun Oct 11 2009, 12:02PM

Registered Member #2081 Joined: Wed Apr 15 2009, 11:36AM
Location:
Posts: 78

hello all,

right i finally got my DRSSTC running for the first time which is fantastic! however, i did a higher voltage test about 200V and have had some big problems since. the driver board appears to be working fine and i can here the igbt's doing there magic, when i apply over 20V to the high voltage side it trips the house voltage. ive changed the rectifire (autho the old one still appeared to be working) and still have the same problems.. could this be the IGBT? have no idea what is causing this please help!

loveHV

Sun Oct 11 2009, 12:17PM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

i always had a problem with the capacity behind the rectifier if its above a certain value the charge current may exeed your breaker current, i don't know you supply schematic but if you single side rectifie and then a capacitor with a value higher then (i think its 450uF )your breaker trips.

a solution is a lightbulb in series with the rectifier with a switch over it. so you can charge the capacitor with a ballast and then close the switch once the capacitor is charged.

hopes this helpes

audio:deviant

Sun Oct 11 2009, 12:30PM

Registered Member #2081 Joined: Wed Apr 15 2009, 11:36AM
Location:
Posts: 78

alright, why do you think it would work the first few times up to 200v and then stop? i replaced it with one of these

loveHV

Sun Oct 11 2009, 12:41PM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

i think its luck because i also had some breaker problems, sometimes it worked and sometimes the breaker trips. what capacity do you use behind your rectifier ?

try the following.

disconnect the IGBT's from the rectifier and cap, then you turn on the main voltage on the rectifier and if the breaker trips try a smaller cap, if it still trips try smaller until it stops tripping.

if the breaker doesn't trips, discharge the cap and try again, if it still doesn't trip then you know the problem is your IGBT bridge.

audio:deviant

Sun Oct 11 2009, 02:00PM

Registered Member #2081 Joined: Wed Apr 15 2009, 11:36AM
Location:
Posts: 78

right it turns out its the igbt's.. authough they still make a sound.. what could have caused this and is there anyway of stopping it? could the cap that goes across the + - terminals be too low? its a 4.7uf 400vdc the big dc cap is 3500uf 450v

also is there a good way of testing the igbt's?

cheers for the quick reply by the way..

doctor electrons

Sun Oct 11 2009, 02:33PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

You can check your igbt's by removing them from the circuit and checking ohms from emitter to collector. If you get a short, or less than
700 kohms then you can assume the igbt is bad. Trust me, i have gotten pretty good at checking them as i have sent about six of them to the graveyard! Good luck with the coil.

loveHV

Sun Oct 11 2009, 03:06PM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

with that 4.7uF cap the breaker shouldn't trip , but with 3500uF its normal the breaker trips. my advise is to use a ballast wich you can later disable with a switch

but with a DRSSTC your gonna need that 3500uF on the + and - rails to supply the current peaks.

do you know the cause why the IGBT's died ?
did your coil work earlier on the 200V ?

if it did and it suddenly stopped and the IGBT's are dead then you should probably check the gate signals with a healty IGBT.

teravolt

Sun Oct 11 2009, 03:24PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

If your igbt's are bad thay will be a dead short and thay generaly go out on pairs. Do you have any way of mesureing the primary current when operating normaly? When you decresed the caps in your string the current probibly went up. how long is your interupter duration? Are your caps ok?

Steve Conner

Sun Oct 11 2009, 07:14PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Do you have a residual current breaker on your house fuse box? You can recognise it by its test button.

If you do, it might well be that that's tripping.

My house still has the old rewirable fuses, where you can put a new piece of fuse wire in when it blows. :D

audio:deviant

Sun Oct 11 2009, 07:51PM

Registered Member #2081 Joined: Wed Apr 15 2009, 11:36AM
Location:
Posts: 78

right ive taken out the igbt's and checked the connection across the emitter and collector, im using a 200k ohm multi meter and i got 16... this sound like it could be a dead igbt. i tested the dc power without the bridge and everything seem to be working, the cap is holding its change and discharging when power is removed, shows the rectifire is still working as well.

what do you guys think igbt's? wish they where cheaper.

was looking at these.

im running a half bridge and 10 2000v 0.33uf caps as an MMC do you think i need more beefy igbt's?

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