HPs vs. WATTs

[pehta]

Please, enlighten me. On this page I read:

1/3 HP Buffing Machine

* 110 volts
* 3450 rpm
* 4.2 amps
* single phase
* 60hz

which can be translated into the POWER by multiplying VOLTS and AMPS. So, 110V X 4.2A = 462 WATTs. Since 1 HP is approx. 740W , the power of the motor is 0.62 HP, which is approx. 2/3 HP and not 1/3 HP.

Is the efficiency of the motor 50% only. I think that electrical motors have efficiency around 80-90%.

So, please, help me out. What is wrong with my calculation ?

[rerod]

Not sure.. Why in the world do you need to know?

[pehta]

Not sure.. Why in the world do you need to know?

..... because I am trying to decide which buffing motor I might buy from Caswell. Every motor has, at least two relevant characteristics: power and RPM. Both are important for buffing.

So, why to buy more expensive 3/4HP motor if the cheaper one has almost the same power (2/3 HP) ?

This is the main reason why I am asking the readers of this forum to help me out.

[Rasper]

If you are going to do any serious buffing you want at least 3/4 hp. If you are going to do any really serious buffing you want more. My main buffer is 2 hp.

R

[pehta]

I am answering my own question. Few minutes ago I stumbled upon a nice site (web page) where you can learn about all you want to know regarding electric motors and then more.

Electric Motor Basics

Just in case if ( or when) the above mentioned web page disappears, I am attaching the compressed file, which contains ALL the data. Since Caswell does not allow more than 97 KB per attachment, I was forced to split the compressed file into three chunks. This post contains FIRST and the SECOND chunk and the 'step by step' instructions how to reconstruct and read the web page on your computer.

Instructions are valid for any LINUX or UNIX based machine.

A) download to your computer ALL three files:
electric_motor_part_1.zip
electric_motor_part_2.zip
electric_motor_part_3.zip

Assumption: you did download all three files into folder (aka directory) /tmp/

Open a terminal (aka xterm.konsole,gnome-terminal)
B) go to /tmp
cd /tmp

C) assemble all three files into one. The following command needs to be typed in to terminal as a ONE LINE.

cat electric_motor_part_1.zip electric_motor_part_2.zip electric_motor_part_3.zip > electric_motor.tar.bz2

D) uncompress the resulting file

tar xvfj electric_motor.tar.bz2

E) start your browser

F) type into URL field of the browser

file:///tmp/electricmotors/electricmotors.html

Enjoy

[pehta]

And the THIRD chunks is here