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'Energy saver' power factoring? - Page 2

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Posted by Jim Wilkins on May 29, 2012, 11:26 am
 


A quick Variac + KAW check on a small bench grinder (no load) gave
about half the current and VA readings at 80VAC as at 120VAC, without
audibly slowing it down much. It would take me a while to set up and
test a household appliance motor. They jump when started unless
clamped down.

The KAWez measured voltage down to 45VAC, where the LCD fades out.

jsw



Posted by Mho on May 31, 2012, 4:37 pm
 
Put the KAW first.

We tested four of these (KaW) units against NBS traceable kWh standards
(0.1% max error..correctable to 0.02% CF) and they were right on the money,
surprisingly enough. They were checked at the usual kWH meter standards =
100% and 50% PF and 2/3  and 10% scale,  but harmonic response was not
testable, at that time.

Very impressive for a $0 gadget.


-------



A quick Variac + KAW check on a small bench grinder (no load) gave
about half the current and VA readings at 80VAC as at 120VAC, without
audibly slowing it down much. It would take me a while to set up and
test a household appliance motor. They jump when started unless
clamped down.

The KAWez measured voltage down to 45VAC, where the LCD fades out.

jsw



Posted by Jim Wilkins on May 31, 2012, 8:11 pm
 

They don't have to be that accurate for battery+inverter testing as
long as they give a repeatable reading proportional to remaining
capacity. The power draw of my laptop varies almost 2:1 depending on
what it's doing, so run times don't tell everything.

jsw



Posted by Jim Wilkins on May 22, 2012, 10:23 am
 

That might be worth trying with a KillAWatt and a Variac, which can
transform lower lowered voltage to higher current efficiently.

This shows how power factor improves as the load on a motor approaches
its design rating:
http://www.motorsanddrives.com/cowern/motorterms16.html

I can't think of many household motors that run lightly loaded often.
My washing machine varies between ~500W spinning empty and ~800W
agitating a full load.

Maybe the metal lathe would benefit when I make small brass parts but
it isn't a common home appliance, rather a typical highly variable
industrial load.

jsw



Posted by Jim Wilkins on May 22, 2012, 8:44 pm
 

Oops, editing error.



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