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What do you usually do when you're going to plug something in the wall?

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LAN_403

Inducktion

Fri Mar 18 2011, 08:50PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

When I say plug into the wall, I mean something YOU built.

I recently made

from neon-john's website, and it works on 12 volts on both sides. I'm deathly afraid of plugging it into rectified mains, though, I'm worried something might go wrong or die.

What do I do to alleviate this problem? I worked quite a while on this so... Worried to lose it all.

The isolation transformer on the schematic has 16+16 turns for the primary and some 8-9 turns on the secondary.
Primary is 12 gauge wire, and the secondary is speaker wire, with both wires soldered together to make 2 strand litz.

The diodes on there, the RPG02 ones, I switched out with UF4007 diodes, and the inductor to the left is actually around 165 uH instead of 200 uH.

Everything else is exactly how it is on the schematic.

James

Fri Mar 18 2011, 10:17PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

Put a lightbulb in series with it. Start out around 60W, if all goes well bump it up to a 100W bulb. Ideally you would scope the current waveform on the primary side of the transformer. A small ferrite toroid with 10-20 turns with the wire you want to measure passed through the center of it will work reasonably well. When you go to run it directly, be sure to use a 10A fuse of at least 250V rating on the input.

Edit:
Isn't the transformer supposed to have 8+8 (16 total) turns? Too many turns is better than not enough turns at least.

Inducktion

Fri Mar 18 2011, 11:08PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

James wrote ...

Put a lightbulb in series with it. Start out around 60W, if all goes well bump it up to a 100W bulb. Ideally you would scope the current waveform on the primary side of the transformer. A small ferrite toroid with 10-20 turns with the wire you want to measure passed through the center of it will work reasonably well. When you go to run it directly, be sure to use a 10A fuse of at least 250V rating on the input.

Edit:
Isn't the transformer supposed to have 8+8 (16 total) turns? Too many turns is better than not enough turns at least.

In his original one he used some 20+20 turns for the iron powder toroid transformer....but I'm using ferrite so 16+16 is probably about right. And like you said, too many turns is better than not enough, otherwise too much current would flow and pop my IGBT's.
And alright, I'll shakily try and use a 40 watt lightbulb, probably will bump it up pretty quickly if it works well. Thanks for the advice.

haxor5354

Sat Mar 19 2011, 04:08AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

take it outside with a really long extension cord and a remote controlled relay switch to turn it on. the worse thing that could happen is your device blowing up.

Turkey9

Sat Mar 19 2011, 05:16AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Did you test it with an isolation transformer for the high power input? If so you're basically already done the light bulb step using the transformer's power rating to limit the input current.

Sulaiman

Sat Mar 19 2011, 05:23AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

If you can give the core cross-sectional area,
the value of the primary resonant capacitor
and the frequency that it runs at on low power
we can calculate whether the core can operate at rectified mains voltage, or saturate.

Do you have a variac?

For this circuit ALWAYS apply the low voltage supply before the high voltage,
and disconnect the low volage supply after the hv has been removed,
or you may blow your transistors.

If the dc inductor saturates you will get hard- (not zvs-) switching which also may kill your transistors.

Dr. ISOTOP

Sat Mar 19 2011, 01:39PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Variac it up.

Inducktion

Sat Mar 19 2011, 05:10PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Sulaiman wrote ...

If you can give the core cross-sectional area,
the value of the primary resonant capacitor
and the frequency that it runs at on low power
we can calculate whether the core can operate at rectified mains voltage, or saturate.

Do you have a variac?

For this circuit ALWAYS apply the low voltage supply before the high voltage,
and disconnect the low volage supply after the hv has been removed,
or you may blow your transistors.

If the dc inductor saturates you will get hard- (not zvs-) switching which also may kill your transistors.

I don't entirely know what happened. I had it all hooked up right, with the low voltage applied before the high voltage like you stated. I had it current limited with a light bulb, and it worked. Without it, the IGBT's went BANG and little bits of silicon flew everywhere. It was rather violent, and even some bit of the trace on the board I made came off. I assume, then, that something caused too much current to flow and thus kill my IGBT's.

And the core is a medium sized flyback core taken from a TV. The resonant capacitor is .15 uF. It ran at about 45 khz on low power. The DC inductor was a 155 uH powdered iron core, two taped together. Yellow color.

IamSmooth

Sat Mar 19 2011, 05:23PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

When testing something new I will have fuses built in that will go before the mains fuse on that line. I also use a variac to slowing increase the voltage. I also have a scope on the critical signals to make sure nothing is going awry.

At this point I will either
1. see the problem and abort before destroying the project
2. the project will blow, but the fuse will protect the line.

Make sure you are protecting your eyes if you think a capacitor or semi might blow.

Martin King

Sat Mar 19 2011, 08:04PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Variac or a long wood (dry) or plastic stick.

Martin.

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