At 02:06 PM 23/08/2012, you wrote:
>Fine.
>So, basically, more current in a field winding should mean higher torque?
>In serially connected winding, that happens naturally, that is, as
>load increases, current increases too, and motor turns with more
>torque, to overcome the load. What would happen if I just feed the
>field winding with a constant current?

It should work fine, but if the motor is designed for series
connection the field voltage will obviously be much lower than
the nominal motor voltage.

>As far as I understand, too strong field does not allow to reach
>higher rpm's - but I do not need them. That motor can turn as much as
>14000rpm, but I really need about 5000 or 6000 max.

With a fixed field current it should act just like a PM motor.
Reduce the field current you get more speed (ignoring losses),
but less available torque. I suppose you could reduce the current
to get higher speed low torque ranges.

As you probably know, this can cause series-wound motors to turn
too fast if operated without a load.

>Sorry, i just do not have a clear understanding how all those factors
>work together.

This might help:http://zone.ni.com/devzone/cda/ph/p/id/46


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