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

turbulatordude wrote:

>>>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.
>>
>>
>
>Hi Guys,
>
>I'm back and reading thru the posts.
>
>The basis starts that the namepalte current is used to hold in
>posistion. Fine, that makes sense.
>
>Noboby argued with what Steve had said that more current is needed to
>overcome the back EMF in the coil, so I'll work with that.
>
>

OK, I'll argue. More VOLTAGE is needed to overcome the back-EMF.

>and it seems the agreement is that more power is needed as the motor
>is acelerated. This is interesting as over the years I have seen a
>lot of people ask why their steppers are missing steps. This
>certainly can be one reason.
>
>The motor we were discussing as 2.4 volts and 6 amps. and we were
>using 60 volts as the DC power supply.
>
>Jon, you mentioned that an acelerating motor can go up to 60 * 7 * .66
>
>

I'm not sure where the 7 comes from. Can you elaborate on this formula ?

Oh, I guess I was thinking of the Gecko's 7 A maximum. In this case it
would
be 60 * 6 * .66

Jon