Re: Electric motors newbie questions


"MDL" <dartkick@xxxxxxxxxxx> wrote in message
news:1182456654.986540.134530@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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:

Actually they are a combination of inductive reactance and resistance. Some
motors can actually present capacitive reactance.

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?

Different motors ... different strokes. Manufacturers often offer dat.

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 *** for)

The best method is to use a dynamometer plus instruments to collect data.
Or, go to the manufacturer.

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?

A locked rotor test measures stall torque/start torque/stall current/start
current.

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.

Google for motor -characteristics, -theory, -dynamometers, -characteristic
curves, -efficiency, -power factor, -torque, -horsepower, -speed and so on.


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