Re: [CAD_CAM_EDM_DRO] Gecko burned - now motor types

Hi Ron,

Most servo drives are chopper drives. A chopper drive works by rapidly
switching the supply on and off. The motor 'sees' the average of the
pulses. There are two main limitations to the amount of torque you can
get out of a motor:

1) The ability of the motor to dissipate heat. If you increase the
current you increase the amount of heat generated (power = current
squared * resistance). Torque is dependent on current. Steppers have an
advantage at low speed as the windings are attached to the body which
acts as a great heatsink. DC motors have the windings on the rotor and
the cooling is very poor at low speed. At high speed air movement
carries the heat away.

2) If the magnetic field generated by the coils is too high the magnets
will become demagnetised. This is permanent and the motor becomes scrap.

Les

R Rogers wrote:

> Thank you for a very informative response. So essentially the brushes in a DC servo motor are a much more direct method in which to switch the circuits within the motor.
> Now, if we used a chopper type drive for a servo (designed for a servo obviously i.e. higher current at idle). would it greatly improve the holding torque? Just a rambling thought.
>
> Ron
>