# Electric motors newbie questions

Discussion in 'Misc Electronics' started by MDL, Jun 21, 2007.

1. ### MDLGuest

Hello, I'm a newbie and I'd like to learn a little about electric
motors.

I've had a run-through of electric motors and I understand the basics
(how they work, that they are an inductive load, etc), but I've got a
few questions:

1. Is there an easy equation or way to find the torque that the the
motor will give out for a given load and voltage/current etc?

2. What information is understood from a motor constant and how is
this found for an arbitrary motor (say, one that I've aquired and wish
to understand but have no spec sheet for)

3. What is a blocked rotor test (besides some sort of test that is
done while blocking the rotor.. I.e. what is measured?) and what is
understood from this?

Maybe I'm just not looking in the right places, but I can't seem to
find any plain English information on this.
If someone could even point me to a good website or something I'd be
extremely thankful.

Cheers,

Matt

2. ### CharlesGuest

Actually they are a combination of inductive reactance and resistance. Some
motors can actually present capacitive reactance.
Different motors ... different strokes. Manufacturers often offer dat.
The best method is to use a dynamometer plus instruments to collect data.
Or, go to the manufacturer.
A locked rotor test measures stall torque/start torque/stall current/start
current.
Google for motor -characteristics, -theory, -dynamometers, -characteristic
curves, -efficiency, -power factor, -torque, -horsepower, -speed and so on.

3. ### Guest

use the current and voltage specs with torque , the eqution for output
is in an physics book. i have one send me the specs you have , i also
have a graphing calculator

4. ### Guest

sorry i didnot read the complete emial. the electric motor should by
manufactor requirements have a serial number on it. depending on the
size and origin of motor determines the place to get the specs , does
in manufactors name appear and is it readable?