Re: [CAD_CAM_EDM_DRO] Re: POWER SUPPLIES

kimvellore wrote:

> Just inquisitive, the specs of the power supply says 1% regulation so
> why add extra caps at the output?. It should have enough inside the
> supply itself to work if operated within the specs. Unless you have
> long wires to the load and have a voltage drop due to wire resistance.
> Anyone have a good explanation for it?

No, the switching-type stepper drivers draw current in sharp pulses.
Swithcing power supplies often have small capacitors inside, and can
accomodate current fluctuations of so many amps/microsecond. If the
current transient has greater slope than that, the servo regulation loop will
either become unstable, or the supply just can't keep up with such
a transient. Therefore, to keep things stable, you really need to insure
that the current transients are within reason. A modest capacitor will
assure that.

Some stepper and servo drivers also allow energy to be extracted from the
motor and returned to the power supply. Under this condition, either a
large capacitor bank or an active energy dump system needs to be
provided to absorb that energy. If not, the bus voltage will rise until
either the power suppy triggers its overvoltage protection crowbar
circuit, or the driver is destroyed.

Jon