Transformerless Power Supply

On Sun, 23 Sep 2018 13:58:37 -0500, amdx <nojunk@knology.net> wrote:

>On 8/10/2018 12:26 PM, amdx wrote:
>> 
>>  &#4294967295; Is it reasonable/possible to build an 8 amp 20 V transformerless 
>> power supply from a 120Vac line.
>>  &#4294967295;I calculate about 180uf plus or minus depending on other components.
>>  &#4294967295;Maybe 9- 20uf caps in parallel?
>>  &#4294967295;I'd like to build it into a leaf blower.
>>  &#4294967295;All plastic, absolutely no metal exposed.
>> 
>>  &#4294967295;I think I've answered my question, I have 12, X rated caps in my junk 
>> box, but they are only 1uf.
>> The cheapest 20uf I can find is $3, so $27 for 9 caps. Not reasonable.
>> 
>>  &#4294967295;Just had another thought, I could mount a power supply with 
>> transformer on the wall and have a cord go to the leaf blower. Just 
>> trying to build a light weight Leaf Blower for the wife to clean the 
>> garage once a week.
>> Daughter gave me the leaf blower after the battery charger gave up.
>> 
>>  &#4294967295;Input encouraged.
>>  &#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295;&#4294967295; Mikek
>
>  I'm still thinking about simple Transformerless supplies for 20V 8 
>amps from 120vac.
>  I recalled this Third harmonic generator, it's design is for very low 
>power, but can it be increased? The design is for 10MHz to 30MHz, going 
>from 60hz to 180hz makes the inductors huge, but... any thoughts.
>> https://bonlacfoods.com/pdf/018180621.pdf
>
>  Here's the two diode version.
>> http://www.wenzel.com/documents/2diomult.html
>
>Lots of reactive power, which means I'm not creating lots of heat.
>But can it be made to work.
>
>                              Mikek
Reactive power works at 60 HZ as well as 10 MHZ the parts just get too
cumbersome and expensive.  The math work very well; the practicality
doesn't work at all.

And you aren't dealing with a fixed load.  Start-up current may be
many times the run current with something like a motor.  You'd
probably end up needing some form of active voltage regulation to make
it work.

If you're talking about inductors you might find selling the copper
windings and iron cores as scrap metal will more than pay for a
replacement power supply.

It (capacitive reactance) is very handy when you just need a few
milliamps to light a LED or power a small circuit like the timer on an
automatic coffee maker directly from mains voltage, but isn't often
used for amps of current because there's better ways to do it.