Re: [CAD_CAM_EDM_DRO] AC drives

hugo_cnc wrote:

>Hi all,
>
>Most of people use either steppingmotors or DC-servo, I noticed that
>the big manufactures (fadal, haas, dmg etc.) all use AC-servo. The
>benefits are more dynamic, more compact, higher peak torque. Are
>there any step and direction AC-drives out there, or is the price too
>high.
>AC-servo motors are synchroonmotors while a regular AC-motor (like
>the spindle motor) is asynchronic, right? Could it be possible to use
>a regular AC-motor as a drive motor, these motor are very cheap and
>deliver a lot of power.
>
>

DC Brushless motors are really misnamed. THEY are truly synchronous
motors. AC servo motors
are VERY similar to ordinary AC induction motors, and they ARE
asynchronous, as they have to be
for the induction principle to excite the rotor. The major differences
are in cooling provisions and
to reduce rotor inertia.

If you had a flexible (ie. programmable) AC servo drive, you could
connect a standard induction
3-phase motor. It may not perform quite as well as a proper servo
motor, but probably would
do fine. You'd need to pull out the internal fan and supply a "boxer"
fan to provide cooling.
A long, narrow motor would probably be better for the inertia situation.
You'd need to provide
an encoder with the exact characteristics needed for the servo drive.
Most of them just need an
incremental encoder with index, though.

Jon