Inverters

[artv]

Hi Everyone,
I'm not sure if this belongs here or in "Controls"
I have 2 identical inverters ,the only stickers say "dc to ac inverter 300w"
Here's a pic of the 2 ends
I was wondering if I can hook these in series to give me a 600watt inverter??
The reason being,... one alone will not run my variable speed drill at max rpm...
I can start the drill (with 1 inverter) but as I increase speed the little "over" light comes on and the little buzzer goes off, shutting down the inverter.
I was going to try it ,but thought I should ask  first in-case I burnt them up too...
I picked them up at a yard sale ,so no real info on them..
Just wondering if they can be hooked in series, or maybe paralell would be better??
Thanks for any input.....artv

[rossw]

Hi Everyone,
I'm not sure if this belongs here or in "Controls"
I have 2 identical inverters ,the only stickers say "dc to ac inverter 300w"

I was wondering if I can hook these in series to give me a 600watt inverter??

Firstly, wiring them in series is unlikely to do what you want, it'd double the voltage.
Secondly, wiring them in parallel is virtually guaranteed to let the magic smoke out.
VERY FEW of the inverters of that size are stackable, they will run out-of-phase and blow up.

[philb]

I'm glad you asked before you tried this Artv.
I asked that same question years ago on another board. Their laughter and scowling did not deter me. I did it anyway. (I have a hard head).

The first two inverters failed in milliseconds with a few pops and then magic smoke came out, just as RossW said.  The next two, I converted their outputs to DC, then ran an 'H' bridge for a square wave. It was involved and just for fun. Oz helped me understand the concepts and also reviewed the schematic, BTW.

That's probably more than you may want to do.

The stackable inverters usually have a provision of some type to link the two together and they are usually proud enough of that feature to list it on the inverters.

[ChrisOlson]

Art, if you do wire them inverters in some series or parallel configuration, please take a video of it and post it to YouTube.  YouTube is a little short on smoking inverter videos and that would add some good content   

--
Chris

[Wolvenar]

Clarification on RossW's post, it would not double the voltage to place them in serial.
It would burn out one, or both, as you are supplying 120v AC to an input that I assume is 12v DC
( if these are american).

If this was simply a set of transformers , which it is not, your would be getting a voltage of 10x *1200v* out of the second in series.

[rossw]

Clarification on RossW's post, it would not double the voltage to place them in serial.
It would burn out one, or both, as you are supplying 120v AC to an input that I assume is 12v DC
( if these are american).

If this was simply a set of transformers , which it is not, your would be getting a voltage of 10x *1200v* out of the second in series.

I think he meant connecting the OUTPUTS in series, wolv.

And yes, the same "adding 3 phase in series" IRP as earlier discussed would probably apply to series connection of the outputs too. But if he was lucky, he could get twice the volts out ..

[WooferHound]

[Wolvenar]

@ rossw ahh ok
the outputs ..

[halfcrazy]

Wooferhound
I think I can teach him how to make more impressive smoke 

I was tasked with pushing the limits excessively early on in the design and testing stages of a new CC and I made some impressive Smoke. I just wish I would have had the video camera handy 

[oztules]

It could be interesting to ponder and test some of this.

If you series the outputs, you will get the sum of the waveforms present. It the output oscillators are exactly at the same frequency, this could be anywhere from 0v to 220v.
It is more likely they are only approx 60hz oscillators in the H bridge stage, and we could see a situation where the voltage fluctuates from 0 to 220 and back to zero.

This may suit Wooferhounds lighting business.... if you put 220v globes on the output, they will glow and die and glow and die, at a rate depending on the difference in the frequencies of the two inverters...

Putting these in parallel will be just a lesson in black smoke, as they have to be synchronised to each other so that they both output the same voltage at the same instant in time....... or poof..

This can only be done by syncing them. A lot of pwm chips do have sync inputs or master slave inputs just for this application of parallel operation..........but these units don't look like they do. 

.................oztules