Subject: Re: VAX7000 3-phase
To: Brian Hechinger <wonko@arkham.ws>
List: port-vax
Date: 03/04/2002 19:09:50
```Brian Hechinger wrote:

> On Mon, Mar 04, 2002 at 03:06:22PM -0800, Chuck McManis wrote:
>
>>Of course something like a TEMCo phase converter could also be used. These
>>types of devices are used in lots of places (machine shops, etc) and can be
>>found used for often 1/3 to 1/2 of their list price. For a small circuit
>>(40 amp) the converter is often < \$1000. It opens up a whole new class of
>>machine for collecting ...
>>
>
> that's cool and all, but how do i convert HP to A?

That's the easy part! Use the following equations:

P = U * I  and 1 W = 1 V * A

1 HP = 550 ft*lbf/s ~ 745.6999 W

> i would need to be able to
> figure out how much HorsePower my VAXen have.  how does one do that?  is it
> based on size?  it takes three horses to pull my vax?  so it's a 3HP model? ;)

One kW are 1.341 HP, so 1 kW at 110 V are 9.09 A.
And then 1 HP at 110 V mounts to 6.72 W. There is
something about the phase issue and how you calculate
effective power (and there is where some conventions
make a difference between VA and W even though they
are the same physical unit.) But I forgot the detail.
It's got something to do with P really not being
U * I but there are integrals involved and capacitance
and inductance turn the phase differences between
U and I around, which makes for differences under
idle vs. load conditions. This was all nice and clear
to me when I did it in school but I forgot most of it
since :-(

regards
-Gunther

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