Oops! You're right! Motors are usually 80~82 % efficient. The Navy seems to be using an efficiency of 75 %.
It should still work both ways once you get the efficiency correct, no? 368 W x 0.75 = 276 W. So, a motor drawing 3.2 A @ 155 V should be able to provide 276 W of mechanical power. Going backwards from 200 W (approx) and using a 75 % efficiency, would result in a need for 267 W of electrical power. At 115 V, that is 2.3 A. Hmmm. You said 3.2 A. Did you mean 2.3 A, and just transposed the numbers? Euric -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of James Frysinger Sent: Sunday, 2003-11-30 11:45 To: U.S. Metric Association Subject: [USMA:27713] Re: Nearly all-metric drill press On Sunday 2003 November 30 11:43, Mighty Chimp wrote: > Well, if we take 115 V x 3.2 A, we get 368 W. Motors are about 90 % > efficient, so multiplying 388 x 0.9 gives us 331 W. Go the other way with your your efficiency. Horsepower is generally used to indicate the rate of work done, not power drawn. For large motors, the Navy figures about 1 kW of power needed to drive a 1 HP motor. Jim -- James R. Frysinger Lifetime Certified Advanced Metrication Specialist Senior Member, IEEE http://www.cofc.edu/~frysingj [EMAIL PROTECTED] [EMAIL PROTECTED] Office: Physics Lab Manager, Lecturer Dept. of Physics and Astronomy University/College of Charleston 66 George Street Charleston, SC 29424 843.953.7644 (phone) 843.953.4824 (FAX) Home: 10 Captiva Row Charleston, SC 29407 843.225.0805 --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.545 / Virus Database: 339 - Release Date: 2003-11-27 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.545 / Virus Database: 339 - Release Date: 2003-11-27
