Re: [CAD_CAM_EDM_DRO] Re: bridgeport series 1 retrofit

On Sat, 10 Jan 2004 21:56:09 -0800, you wrote:

>Guys -
>Couldn't two diodes be placed in parallel - one to drop the voltage he
>wants to drop and the other ('pointing' in the other direction) to prevent
>the buildup you speak of ?

Yes, although if you want, it's easier to place the diodes between the
bridge rectifier and the capacitor. You need less diodes and you get
the same effect. Be aware that the diode will dissipate heat, roughly
0.8 x the maximum amperage you expect watts, and will probably need to
be mounted on a heatsink like the bridge rectifier.

Harvey

>
>Myron Cherry
>
>
>----- Original Message -----
>From: "bull2003winkle" <bull2003winkle@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Saturday, January 10, 2004 12:29 PM
>Subject: [CAD_CAM_EDM_DRO] Re: bridgeport series 1 retrofit
>
>
>> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>> >
>> >
>> > Bob Japundza wrote:
>> >
>> > >Guys, thanks for the responses. Sounds like having a closed loop
>> > >feedback system the way I described might be not worth the effort.
>> > >But I do plan on installing the DRO anyway. On the power supply I
>> > >may just add some diodes in to get the voltage drop.
>> > >
>> > You can't do that. The diodes prevent any energy returned from the
>> > motors to the drives from being stored safely. The small capacitance
>> > in the drives can't contain much energy, so the voltage quickly rises
>> > to damaging levels. When large motors are decelerated, they can
>> > return energy to the drive.
>> >
>> > Jon
>>
>> Jon is right about the diodes. If you want to drop a small voltage
>> there's a better way to do it. Put a very small value resistor in
>> series between the transformer and the bridge rectifier. It has the
>> added benefit of reducing the peak current in the bridge and
>> capacitor. Even very low values will dissipate a lot of power.
>>
>> Ken
>>
>>