Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Thu, 18 Jul 2002 14:22:49 -0400
Message-ID: <redirect-1641238@logan.com>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
From: "Dan Schaefer" <dfs155@earthlink.net>
Subject: IVP JET Prop questions
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FWIW:

For you folks looking for a 2 HP motor to drive a compressor: a quick
calculation will tell you how much current (Amps) your electrical system
will need to supply.

1 HP equals about 750 watts. If the motor is 100% efficient - good ones
might go as high as 80 - 85% - the current draw for an average 80% efficient
1 HP motor on a 28 volt system is roughly (750/0.8) / 28 = 33.5 Amps, so
twice that for 2 HP or (approx.) 67 Amps. If the motor is 90% efficient, the
current only drops to about 59.5 Amps.

For a 12 volt system, just double the above current figures.

In addition, these are just the steady-state numbers. Most, if not all, DC
motors will draw a large inrush current for a short time when energized as
they get up to speed - particularly if starting under load - as might be the
case running a compressor. The peak and duration of the inrush is hard to
quantify as it depends on the particular motor design and the nature of the
load.

Dan Schaefer