RE: [CAD_CAM_EDM_DRO] Re: dc spindle motor control.

On a side note... My understanding is that, in general, it's a real bad idea
to regulate an inductive load, such as a motor, with any kind of resistance,
such as a rheostat. Is that still the prevailing logic?

Andrey

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: Thursday, August 11, 2005 1:26 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: dc spindle motor control.

jeff35m_73068 wrote:

>I picked up a 500 watt reostat to control this manually. Is the
>lowering of field voltage goint to produce the increase in speed I
>want?
>

Theorietically, yes, but the field is designed for tens of amps at a
fraction
of a volt. And, a series-wound motor does not regulate speed
well, so it is a bad choice for a machine spindle.

> What type of control would you suggest? Do you think it
>possible the fields run off the 3rd wire from the armature?
>
>

I kind of doubt it. What is the 3rd wire connected to? A 3rd brush?
Seems highly unlikely. I'd guess your 3rd wire is a safety ground.

Jon



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