Re: [CAD_CAM_EDM_DRO] Re: Servo motor maximum voltage rating

mariss92705@... wrote:

> Hi,
>
> I said current should be limited to the motor stall current at its
> rated voltage (rated stall current). An unlimited current a higher
> than motor rated voltage will result in a stall current that can
> demagnetize the motor.

Limiting current to continuous rated current of the motor reduces
the system performance significantly. This is not standard industry
practice. Higher end servo drives have provisions for integrating
motor dissipated power over a moderate period of time. they will
either shut down or reduce the peak current when the limit is
reached. Unlimited current at even a few volts can demagnetize
the motor. As long as the current is firmly limited to the motor's
PEAK current, the magnets will not be harmed by demagnetization.
The motor can still be cooked, however. Careful selection of
time-delay fuses can mostly cover the case of a system with
current limit set near the motor's peak current limit, when an
abnormal condition (crash) ocurrs. Generally, when a crash
ocurrs, either the CNC control detects excessive position error
and calls for E-stop, or the servo amp detects a sudden rise
in current past the fault limit, and shuts down.

Jon