RE: (ET) Inverter for Electric Chainsaw

["Elie, Larry (L.D.)" <lelie ford com>]

Ha ha.  That 'peak' doesn't have much to do with the rate at which work 
can be done.

The torque is proportional to the current that ACTUALLY PASSES through the 
armature.  You can't 
goose up that current without a higher input voltage due to the internal 
resistance of the wires. 
If you bring in input voltage to 200V, you will get more current through 
the wires for a while... 
Until something melts.

I used to argue that one could do better by using a square wave input, but 
that's not really useful 
as the current STILL can't rise any quicker in any one cycle because of 
that same resistance.

The actual power the motor puts out is proportional to the product of the 
torque and the rotational 
speed.  At 0 RPM (stalled) the power output is 0, even though the torque 
may be huge.  The peak power 
is indeed usually at slightly reduced RPM.

Larry Elie




-----Original Message-----
From: Humphrey, Timothy [mailto:HumphreyT neads ang af mil]
Sent: Monday, April 14, 2003 3:56 PM
To: Elec-trak Mail List
Subject: RE: (ET) Inverter for Electric Chainsaw


That 120volts RMS equals 170 Volts Peak, so 170 * 10.5 = 1785watts  or 2.4
peak horsepower.

It's probably quite a bit higher than that actually. If your breaker is a 
20
amp breaker then that means your peak is more like 4.5hp. But a breaker
won't trip instantly like a fuse will so you may be able to put even more
power to it say 30 amps for a second or two = 6.8hp.

Try it, put your chainsaw on a good large hardwood log, or if you really
want to impress somebody use pine. Pull the trigger and push down with all
your might, trying to stall the motor. For real fun have a friend race you
with a gas saw rated at twice the power.

Remember these saws weren't meant to be run this hard so don't do it this
way continuously. Unless you want to replace it anyway. Once or twice to
prove a point won't hurt it. I've done it on 9 inch red oak and my saw is
still going. This log would stall my Mccullouch 35cc, but my 2-1/4 
Remington
went right through it.

I only wish it had a chain break. I get tired of waiting for the chain to
stop so I can set the saw down. 


Don't get me wrong. I also think that the advertisers claiming elevated
power levels on these devices are misleading. But, If the ICE crowd can
exxagerate their power levels then why can't "we".



Stay Charged!

Hump       

> -----Original Message-----
> From: David Roden (Akron OH USA) [mailto:roden ald net]
> Sent: Monday, April 14, 2003 1:41 PM
> To: Elec-trak Mail List
> Subject: Re: (ET) Inverter for Electric Chainsaw
> 
> 
> On 13 Apr 2003 at 21:34, Herb Crary wrote:
> 
> > I have an electric chainsaw rated at 2.5 hp;
> > the rating plate says 120v 10.5 amps. This must be one of 
> those bogus rating
> > systems, because this is only 1260 watts or about 1.7 hp 
> (746 watts = 1 hp).
> 
> Bogus it is indeed.  Maybe that's the peak hp the motor can 
> sustain for 
> about 500 milliseconds, but you can't do any real work with 
> it; those horses 
> tire out too fast.  <g>  
> 
> I don't think there's any law regulating what manufacturers 
> can claim for 
> motor output, so for a lot of consumer products they just 
> just plain make 
> things up.  
> 
> GE did it too, with the bizarre claims for the E-15 that "peak torque 
> exceeds 15hp," as if torque were measured in horsepower.  I 
> suppose they 
> were trying to claim that the peak torque was higher than 
> that of a 15hp gas 
> tractor, but that's not what they said.
> 
> 
> David Roden - Akron, Ohio, USA
> 1991 Solectria Force 144vac
> 1991 Ford Escort Green/EV 128vdc
> 1970 GE Elec-trak E15 36vdc
> 1974 Avco New Idea 36vdc
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