Re: Plasma table gear reduction

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
wrote:

>
>
> > > Les
> >
> > I don't see that as a problem. An external fan would suppliment

any

> > low speed heating problem. But then knowing to solve a problem is
> > half the battle !
>
> An external fan won't necessarily take care of that. Due to the
> I(squared) function, doubling the current results in 4X the heat
> generation. Heat transfer functions are complex, non-linear, and far
> beyond the scope of discussion here, but suffice it to say that,
> essentially, the amount of heat transferred to the outer surface of
> the motor is a function of the temperature gradient from the

armature

> to the outer case surface. The only way to keep that higher
> temperature gradient is by allowing the armature to run at an

elevated

> temperature (which it will for sure). The problem lies in the fact
> that it won't run that way for long. Large DC spindle motors, etc
> which have to be able to run heavily loaded at a fraction of their
> design speed most always incorporate positive pressure centrifugal

fan

> systems for forced air cooling of the motor internals as part of the
> motor itself. You have to be able to cool at the source of heat
> generation, because there is no direct path for conductive transfer
> (the most effective means of heat transfer) from the armature to the
> case surface.
>
> //// Discussing this servo heating issue and contemplating methods

to avoid it are redundant. It's like leaving a car in 4th gear and
discussing the unusual clutch wear. Thanks for taking the time to
discuss a very complicated subject in a surrounding of lesser
intellect. I for one appreciate it.

>
> ////Ron

Considdering that all engineering is the art of compromise, the topic
has expanded my awareness considderably.

I am still weak on motors but that is partially the learning curve.

I really appreciate everybody taking the time to explain things about
how this or that is done.

Dave