Re: [CAD_CAM_EDM_DRO] Re: Power Supply for 4-axis CNC stepper driver

turbulatordude wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Steve Stallings"
><stevesng@n...> wrote:
>
>
>>Weedy,
>>
>>Your transformer selection is close to what I would recommend, but
>>not for the reasons you expect.
>>
>>
>
>
>
>Interesting. If the motors are 2.4 volts and 6 amps or 14.4 watts
>times 4 motors for 57.60 watts total, why is the secondary selected
>for 1,032 watts ? (43 volts times 6 amps time 4 motors ?) why not
>the 60 VDC final voltage times 6 amps times 4 motors ? (1,440 watts?)
>
>

The 14.4 W (plus some iron losses in the motor and switching losses in
the driver) is the power dissipation when standing STILL, only. When
accelerating,
the power requirement (that's not all loss, the motor's shaft is
delivering real
power) goes up dramatically. It can rise to about 60 * 7 * .66 = 277 W
per motor. Except under exceptional conditions, it is pretty hard for a
machine
to require this kind of power for very long, however. So, a power
supply that can
deliver that power (X number of motors) for only an instant will do OK.
Bulk,
unregulated power supplies are easily capable of delivering short bursts of
power above their continuous ratings.

So, the worst case load would be somewhere around 1100 W (277 * 4 axes),
but a power supply with a conservative 600 - 800 W rating should be
completely
adequate for a milling machine. If you were building a high-speed
router, it
might be better to plan for 1000 W rating, as these machines tend to really
keep the motors spinning fast.

>
>

Jon