Re: [CAD_CAM_EDM_DRO] Re: Re: Re: DC versus 3 Phase

beer@... wrote:

> I do agree that the VFD has a lot of RF hash .. A LOT.
>
> Here's how much. I initially routed the 110 v power line into my
> machine, to a power switch, and then back out to the VFD. Tied
> together with cable ties was a SHIELDED line with four wires running
> to a stepper motor.
>
> When the VFD was turned on, the stepper would "jitter"! Surprising,
> especially considering that THE STEPPERS WERE NOT POWERED ! This was
> not noise being fed back into the controller and causing spurious
> steps, it was energy induced from the 110V line into motor leads.

WOW, that is some SERIOUS EMI! Moving a stepper motor with induced
currents! (I suspect there is really a more subtle effect, including the stepper
drivers. I suspect the EMI from the VFD was building up enough voltage, through
the diodes in the stepper driver than normally prevent stepper wires from exceeding
the DC supply voltage, that it was actually partially powering the stepper driver.
Then, the stepper driver would turn on a transistor or two and dump what was
in the capacitor to the motor. But, still, that's POWERFUL EMI!)

Jon