Re: (ET) Harry's suggestion of using DC to power 115VAC devices

["S. Frankenfield" <sf bright net>]

I've used variable speed triggers on DC with no problem. It just runs at 
full speed.
It's true that the switch is more stressed with DC than AC. But if you're 
worried about it and can get inside, you can put a capacitor across the 
switch to solve the problem. I haven't bothered. And if it's a sliding 
contact type of switch, it probably won't be a problem.

Harry

>From: jim <fiskfarm mediaone net>
>Reply-To: fiskfarm mediaone net
>CC: elec-trak cosmos5 phy tufts edu
>Subject: Re: (ET) Harry's suggestion of using DC to power 115VAC devices
>Date: Sat, 30 Sep 2000 10:30:51 -0400
>
>Not sure if this was mentioned but never use a tool with a variable speed 
>trigger
>as well as you can kiss the variable speed solid state unit good-bye. 
>Been there
>and done that with a Magnum Hole Hog on a DC alternator rig. Situation 
>would be the
>same off the ET and a DC 120 unit.
>
>Jim

>
>Steven Naugler wrote:
>
>> To Harry and the "List",
>>         One potential danger of using DC to power tools sold for 115VAC 
>> use that
>> have universal motors is that most have AC rated power switches.  An AC
>> rated switch will fail prematurely when used on DC, sometimes by welding
>> closed (on).  The problem is that AC switches depend on the current
>> dropping to zero 120 times a second.  At that zero current any arcing
>> stops.  The same switch on DC has to break the current at full current
>> because (sorry for being obvious) the current never drops to zero with 
>> DC.
>> A DC rated switch generally has larger contacts.
>>         I am not saying you should not use these tools on DC, but 
>> rather be
>> careful unless you know the device was designed for both AC and DC use. 
>>  If
>> an AC switch when used with DC fails there is a high likelyhood of 
>> failing
>> welded in the on position.
>>
>> Steve Naugler
>> snaugler earthlink net
>>
>> > [Original Message]
>> > From: harry landis <hlandis hotmail com>
>> > To: <elec-trak cosmos5 phy tufts edu>
>> > Date: 9/28/00 9:25:07 PM
>> > Subject:
>> >
>> > To the list:
>> >
>> > I suppose since there is a flurry of interest in inverters, I will 
>> > put in
>> my
>> > two cents. I built a device last spring that solved the problem for 
>> > me.
>> > Since I don?t want to use anything except tools with brush type motors
>> with
>> > power from the ET, I don?t need AC. So I took 4  Vicor 150 watt 48v 
>> > to 48
>> > volt dc-dc converters and connected the inputs in parallel and the
>> outputs
>> > in parallel. (They are made to run on 36-72 volt input, but actually 
>> > work
>> > down to 28v) So now I have 600 watts (12 amps) of 48V isolated power.
>> Then I
>> > took a 48v to 15v 150 watt (10 amps) converter and wired the input in
>> > parallel with the other inputs, and put the output in series with the
>> other
>> > outputs. So now I have 10 amps or more of 63 volt power. Now I put 
>> > this
>> > output in series with the battery pack. Now I have 10 amps or 
>> > more(1000w)
>> of
>> > 99v DC power. Which is just about right to run universal motors. They
>> prefer
>> > it to 110 AC. Better life, more power, fewer losses. The converters 
>> > cost
>> > about $100 ea from Vicor. I have about enough surplus ones to make 
>> > maybe
>> 2
>> > more converters. They are about *? x 3? x 5?. It?s called a full brick
>> > package. You can probably find them on the Vicor site. I screwed them 
>> > all
>> to
>> > a 1/8? aluminum plate that sits across the front of the E12 under the
>> hood
>> > (over the batteries). It doesn?t get in the way of anything. The 
>> > input is
>> > taken from the PTO outlet. The output is an outlet on the plate.It 
>> > also
>> has
>> > a switch/circuit breaker to turn it on and protect it from overloads. 
>> > The
>> > converters are 85% -95% efficient.  It has worked fine from the 
>> > moment I
>> > first turned it on. I use a weed whacker, chain saw and rotary hammer
>> with
>> > it, no problem. I haven?t seen a source of these things surplus. I got
>> mine
>> > in a one time deal. I suppose I would part with a set for  $150. The
>> buyer
>> > would have to make the mounting plate and wire it all together. I
> > probably
>> > also have a circuit breaker and  outlet.
>> >
>> > Harry Landis
>> > _________________________________________________________________________
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>>
>> --- Steven Naugler
>> --- snaugler earthlink net
>

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