Ac Motor Control

HI,
Need basic info (theory) on ac motor drives. Could you guys tell me a
good web site to look at or a book? Input on AB 1336 would also be
useful.
Thanks,
Charles

Try RSDorans site

http://www.patchn.com/motors.htm

Cheers

VFD drives are devices that take power from the line,
convert it to DC, then convert DC to three phase AC.
Frequency of the 3-phase output can be changed at will,
usually in range 0-250Hz. Frequency vs. motor speed is
linear relation (same motor will turn twice as fast at 60Hz,
compared to 30Hz).
Now how do we control it? Some drives have analog input,
changing input from 0-10VDC can change motor speed 0-100%
for example. This type of drive is usually called
analog follower. Note that not all drives do this, but all
drives do have option to set one, two or more (usually up to
16) different frequencies that can be selected through
digital inputs using binary code.
Drive can be configured to use certain acceleration,
deceleration, braking etc. when moving from one to
another frequency.
It is up to you to choose manual push buttons or PLC outputs
to control it. Many new drives and not so many older ones come
with communication ports so paramters can be changed at will.
Note that most motors don't like to stall or run at very low
speeds for prolonged time or they burn (not enough air
circulates through the motor to keep the coils at acceptable
temperature levels).
There are also drives that can be programmed in ASM or C or
similar language to perform appropriate (sometimes complex)
action when certain input is active.
Some drives can have encoders wired directly to drive etc.
I hope this is enough to give you idea about what VFD is
all about.
1336 is AB drive so you can go to www.ab.com/manuals/
to download manuals and learn more about model you have.