Use of 12VDC-120VAC non-sinusoidal inverters

[analogkid2digitalman]

I'll be travelling off-site from work where my primary power source is 12VDC automotive. Was considering using a few hundred watt non-sinusoidal 12VDC to 120VAC inverter to power the battery chargers for the laptop and camcorder.

However, reading the manuals for the laptop/camcorder, they advise against the use of such inverters since overheating and damage may occur. Are these warnings justified? Any good or bad personal experiences?

Thanks

-AK2DM

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"It's the questions that drive us"
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[ScottyUK]

If the chargers incorporate a mains-frequency transformer then the chances are the square or quasi-square output from the inverter will cause additional heating in the iron core. If they're switchmode then they will probably be ok, unless they are switchmode with active power factor correction in which case the magic smoke might irreversibly be let out.


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If we learn from our mistakes I'm getting a great education!

 

[MacGyverS2000]

Non-sinusoidal... generally bad for electronic equipment of many kinds. As Scotty says, you may be okay with a generic, low-power switchmode (no motors), but it's a gamble...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

Dan I beg to differ - Non-sinusoidal is good for rectifier front ends. Most any non-PFC switcher front-end would not care a twit.

The PFC ones? They would care a lot! (briefly)

Keith Cress
kcress -

http://www.flaminsystems.com

 

[resqcapt19]

You might consider a motor/generator unit like this one.

http://www.rediline.com/redilit.

As I recall they are pricey, but rugged. Many of the power utility trucks in this area use them.

 

[VEBill]

It's less frightening to give them a try if those chargers happen to be the type where replacements are cheap (for example, US$9 with free shipping from Hong Kong).

Obviously try open circuit, laptop and camcorder not connected, to start - watch for failure and check output voltage.

Then monitor for excess heat under worst case (charging and operating at same time).

 

[analogkid2digitalman]

Thanks for the feedback.

Looks like my concerns may be justified.

Not sure if they have active PFC, I think I will play it safe and try to obtain 12V powered chargers from the manufacturers.

Could alway record a 60Hz sine on my MP3 and play it back through the stereo and tap off the subwoofer amp to power the chargers

Thanks Again

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[Noway2]

If you have the capability, put a scope on the current signal into the supply. If it is non PFC you will probably see a lot of 3rd harmonic from the rectifier.

 

[catserveng]

I have an invertor on my truck that is cheap one from Harbor Freight(company didn't want to spring for an expensive one) and used daily to run power tools, cordless tool chargers, laptop charger. So far no issues except with some of our older test equipment, however using a good temporary ground has resolved that issue.

 

[Skogsgurra]

I don't see any reason why devices with PFC should care. Unless you have passive PFC, which you never have in small chargers and mains adapters born this millennium.

The active PFC simply tries to draw a current waveform from the source that is similar to the voltage waveform - and in phase with it. That can hardly be a problem.

It could be a problem if the source impedance were low (PSCC high), but it is not in a device rated a couple of hundred watts and which is fed from a 12 V battery. Probably also with some resistance in the connecting cables.

I have used inverters with square wave, stepped (stair-case) square wave and also sine outout. Of those, the sine output inverter died quickly. But the square wave and stepped square wave inverters still live. And I have not killed any load connected to them so far.

The best solution is to buy 12 V mains adapters for your computer, phone and what have you. All you need an inverter for then is your specialized measurement equipment. That part, I have solved by using USB instruments. They are smaller, lighter and better in many respects than their mains-fed brethren. At least if you work with signals below a few hundred MHz.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

skogs,

My former colleagues in the IT department put one of their expensive rack-mounted active PFC-corrected UPS units on the output of the central UPS (stupid idea I know, but...) and their UPS front end burnt up. The central UPS was a rather poor design and the output voltage had a triple zero crossing and massive distortion which the active PFC tried unsucessfully to follow. I don't know if all active front ends try to mimic the voltage waveform, but those that do seem to be optimised for sinusoids.


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If we learn from our mistakes I'm getting a great education!

 

[Skogsgurra]

Yes Scotty, I can believe that.

A central UPS usually does have a low internal impedance. What I was discussing - and I hope what the OP meant - was the small 100 - 200 W units.

Quote: "It could be a problem if the source impedance were low (PSCC high), but it is not in a device rated a couple of hundred watts and which is fed from a 12 V battery. Probably also with some resistance in the connecting cables"



Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...