Re: [CAD_CAM_EDM_DRO] Re: VFD?

In a message dated 8/30/2005 1:27:39 AM Eastern Daylight Time,
jdelaney2@... writes:

You can over speed your motor. People routinely run at 120 hz. with
standard bearings, but the older the motor the more risky this is of
course. Heat is the enemy. Bearings that are not rated for double the
RPMs could be at risk, maybe.

Running at low speed for prolonged periods can be risky too 'cause
the fan is not spinning as fast as it should be. But you could be
cranking out as much energy.



Keep in mind that if you are going to use a VFD, it is advisable to use a
motor rated for VFD use. They are designed so they can be run at lower speeds
and with less "noise" than standard AC motors. This helps to reduce the
possible damage when running at higher frequencies and at very low ones. Your
OEMs use VFDs pretty much anywhere they need to change the speed of a motor and
even for fairly precise positioning of certain components of a machine. I
wouldn't recommend using them on mill or router axis of course. However, if
you are moving something to a certain measured position then stopping it and
leaving it there to make the cut (this is done in woodworking on tennoners,
moulders, panel saws, etc.) they work quite well. By the time you factor in
the cost of a motor with two speed and an electro-mechanical brake built into
it, the cost of the VFD is usually less and works as well or better.

Well, my two cents worth.

Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone / Fax: 770-974-5295
E-mail: cnc002@...

I furnish technical support, repair, and other related services for your
industrial woodworking machinery. My background as Senior Service Engineer for
the SCMI Group for nearly fifteen years with factory training, combines with
my extensive background in electronics, mechanics, pneumatics, electrical and
CNC machinery to offer you needed support for your machinery.


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