Re: 110VDC Supply?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Kenneth Cardolino"
<kdntool@c...> wrote:

> Question for the experts. What is my best bet for deriving 110 VDC
> from 120 VAC? 77 volt secondary transformer with bridge and cap? I
> need @ 6.5 cont. amps for driving the DC spindle motor on my mill

via

> PWM.
> Thanks in advance!
> Ken

If the secondary voltage is 77VAC it will rectify out peak of about
108 VDC at the filter cap. If the number you gave is after
rectification and filtering then it will be hard to get there with
that transformer.
A lot of the spindle motors are driven from transformerless small PWM
controllers. There are always some for sale on ebay. Down side is
that they are not isolated (share same ground and neutral) but if the
conrol is fully enclosed it's considered safe. If you are looking to
control the DC output remotely for spindle speed control from the
computer then the non-isolated control can cause real problems. You
will have to opto isolate the PC signal and let the electronics on
the motor control side (PWM to voltage card) be referenced to the
motor side DC-. Make sure the case on the DC motor is not
electrically connected to either of the motor inputs.