Help on tapping 300V DC out from 12-220V power Inverter

[VegasF6]

Re: Help on tapping 450V DC out from 12-220V power Inverter

Thanks for all the concerns, guys. The 9V story is interesting, didn't know breaking the skin
make such a big difference, so going forward, we should never play with electricity with a cut & band-aid on.

With the skin on, electricity travels along the skin, so 110 shock rarely kill people unless one touch the wire with palm & close on the wire due to muscle contraction.

Some electricians in Asia countries test 220V AC wires with bare hand some times, the rule is always test with back of the hand, the shock will bounce the hand away. Never touch with palm, as muscle contraction will cause grabbing the wire & won't let go

I am sure most of you have felt the jolt from 110V AC some time during your life?
DC Volt risk is rated roughly as 1/3 of AC risk, so 330V DC is about 110V AC in risk, which is lower risk than 220V AC. But still, I am not under estimating the risk, I'll be extremely careful.

That's doing it old school yo! Hah. Don't forget to always keep the other hand in your pocket or behind your back. At least, that's what the old timers have told me. Somehow, they were still alive to tell me this. You know, the guys that can't be bothered to shut off 480V while they hookup a circuit cuz it would slow production.

Oh P.S. I am not so sure those latex gloves are affording you anything other than a false sense of safety. I am not gonna harp on it or anything, just want to point it out.

 

[italianboy]

Re: Help on tapping 450V DC out from 12-220V power Inverter

You could just access the other side of the board and solder the two wires for high voltage DC in parallel to the two leads of the 450V-rated capacitor. Be sure not to short them to the outer aluminum shell!

 

[ma_sha1]

Re: Help on tapping 450V DC out from 12-220V power Inverter

The back is not easily accessible as 5 resistors are thermo glued to the frame.

I measure the resistance between the - of the rectifier and - of the 12v in, it's Zero.
So I think it's the same to use either one.

 

[MikeAusC]

Re: Help on tapping 450V DC out from 12-220V power Inverter

If you get shocked you should know that you should call an ambulance and get to a hospital to be monitored. Electrical shocks can cause small arrythmias that can lead to cardiac arrest up to 48h after the incident so proper monitoring is critical in that period.

Unfortunately I can verify the seriousness of that recommendation - sadly a colleague of mine died that way many years ago.

 

[MikeAusC]

Re: Help on tapping 450V DC out from 12-220V power Inverter

. . . . Some electricians in Asia countries test 220V AC wires with bare hand some times . . .

Some people play Russian Roulette and live . . . . but there's no way I would suggest people doing that either !!!

 

[saeckereier]

Re: Help on tapping 450V DC out from 12-220V power Inverter

Unfortunately I can verify the seriousness of that recommendation - sadly a colleague of mine died that way many years ago.

Sorry to ask, but is this something you witnessed first hand? (not the shock but the consequences) I have heard some reports of this and I have been taught this in training but so far I only heard third hand accounts.

 

[MikeAusC]

Re: Help on tapping 450V DC out from 12-220V power Inverter

Sorry to ask, but is this something you witnessed first hand? (not the shock but the consequences) I have heard some reports of this and I have been taught this in training but so far I only heard third hand accounts.

No witnessing. He received an electric shock from 240 volts which threw him, while working on a washing machine. Went to hospital and was discharged. Went to work the next day. Died suddenly the following day.

 

[saeckereier]

Re: Help on tapping 450V DC out from 12-220V power Inverter

What I meant was this is not some story someone told you but you knew this colleague and know that the accounts are legit?

 

[ma_sha1]

Re: Help on tapping 450V DC out from 12-220V power Inverter

OK, I decided to wire the Neg. to the "-" end of the rectifier instead of 12v "-" in.
I cut the AC out wires & re-wired to the 300V rectifier tapping, this way, I can plug in a beefy AC cord for the 300V DC, so it's more safe.

There are total of 7 identical looking square power resistors & 6 of them were heat sinked to the wall, for some reason one is not. I don't know if that's some kind of negligence? As they all look identical. So I decided to heatsink it to the wall with a copper pad, as I'll be driving it pretty hard & don't want to risk one of them become the weakest link.

Biola, it's a success! I actually got a few more volts wiring to the rectifier neg.
Thanks very much for all the help!

 

[BoarHunter]

Re: Help on tapping 450V DC out from 12-220V power Inverter

Where are you getting this nonsense from?

As has been pointed out any voltage high enough to disturb your heart rhythm is dangerous, potentially lethal. That includes 110 V AC.

Yes, many of us have been jolted by the mains, even 240 V, in our lives. That does not mean 240 V is safe, it just means we have been lucky.

This non sense comes from the epic argument between T Edison promoting its DC power distribution system to N Tesla promoting AC !

Note that the reason why the US did not upgrade to 220-240 AC in the fifties was also because of the safety argument.

In the EU, to reduce the risk, distribution has been done in 2 X 220 AC and 3 X 220 AC with the neutral grounded. As accidental contact is usualy between ground and phase, you get 110 and 127 respectively.
In fact it started in Germany. It allowed almost a doubling of the current carrying capacity without changing the wirings.
Better protection mechanism (differential breakers) have allowed to go 3 X 380 AC, the 220 now being between phase.

You can survive a 220 electric shock as I experienced it at age 17 while tuning a tube radio but you learn to be extremely cautious. And yes, always the left hand in the pocket, proper rubber sole, even when I use my electric razor !

 

[HKJ]

Re: Help on tapping 450V DC out from 12-220V power Inverter

In the EU, to reduce the risk, distribution has been done in 2 X 220 AC and 3 X 220 AC with the neutral grounded. As accidental contact is usualy between ground and phase, you get 110 and 127 respectively.

No, around there we have 230 VAC from earth and 400 VAC between phases in a 3 phase system. Ordinary household stuff uses the 230 VAC.

 

[BoarHunter]

Re: Help on tapping 450V DC out from 12-220V power Inverter

No, around there we have 230 VAC from earth and 400 VAC between phases in a 3 phase system. Ordinary household stuff uses the 230 VAC.

You didn't read my full post ! I said that after this first change (completed in the sixties), we migrated to 220 phase to neutral,with 380 between phase (from a 3 X 220 AC to 3X 380AC). No change for regular lighting and household appliances but big change in the industry as motors ahd to be changed.
As there is always a few percent tolerance, a few year ago, the old upper limit became the standard average that is 230 AC with 3 X 400 AC distribution.

Copper is expensive, so without changing the wiring, you carry more power and also EU harmonisation because of the power grid covering all of Europe.
And Germany needs the nuclear electricity they frown upon, from France

 

[Russel]

Re: Help on tapping 450V DC out from 12-220V power Inverter

[...]You can survive a 220 electric shock as I experienced it at age 17 while tuning a tube radio but you learn to be extremely cautious. [...]

The point is that electricity can kill!

 

[Walterk]

Re: Help on tapping 450V DC out from 12-220V power Inverter

I understood what you where doing here.
Now, at second reading I understand why you want the 300V.

What will runtimes be with 300W ...?

 

[ma_sha1]

Re: Help on tapping 450V DC out from 12-220V power Inverter

Battery is 20AH Lifepo4 e-bike battery. 13.3V
300W pulled from 13.3V battery = 22.5 Amp. It'll run close to 1hr.

 

[HooNz]

Hi all you Experts on safety , one should be aware that 220/240/110 ac is the RMS or equivalent DC voltage of said things , i am happy to read all the safety concerns of these dangerous voltages mentioned , as i would have HaTed to have been touching something on the peak of a sine-wave which would have been 220vac rms x 1.414=311v , 240vac rms@340v or 110vac rms@156v but only on those sneaky peaks! .
To op , good work there , i am glad that you did not use the dc common earth/rail as quite a-lot these days are separate due to extra safety concerns.

http://www.animations.physics.unsw.edu.au/jw/power.html

There is a old Indian saying that goes like this .
Those that eat dry crackers in bed Get crumby sleep .

 

[Walterk]

Hi all you Experts on safety , one should be aware that 220/240/110 ac is the RMS or equivalent DC voltage of said things , i am happy to read all the safety concerns of these dangerous voltages mentioned , as i would have HaTed to have been touching something on the peak of a sine-wave which would have been 220vac rms x 1.414=311v , 240vac rms@340v or 110vac rms@156v but only on those sneaky peaks! .
To op , good work there , i am glad that you did not use the dc common earth/rail as quite a-lot these days are separate due to extra safety concerns.

Thanks for the clarification.... I think....to put it in surfing language;

Do you mean they all pose similar danger as they all share same wave heights at moments?

 

[HooNz]

Exactly , moments in time , generally in Hertz or cycles per second , an example is if one froze time at the exact peak of the wave with 340v(240vac) measured on the multimeter one could Safely poke your finger on it and NOT receive a shock , as at that time there in no current flowing at all (water volume) but there is still pressure (volts) but for 60hz or 50hz line frequency here it is to fast , on the rise just before the peak or just after the peak is really where the dangerous to biological things is as for people , it is suggested that just 50ua (at 240vac) across the chest can stop the engine of the hydraulic system , so just around the peak of the wave is 340v not 240v.

And of course the opposite is valid in frozen state at the 0 crossing point with all current and no voltage , sneaky peaks.

Another peak is winter , safely walk on thick ice in relative terms , the trough or 0 crossing point is just before summer :naughty: , its all Waves , even earth @ approximately 8hz .

But the main underlying source is "Do not poke finger In" :wave: