On Wed, 06 Jan 2010 21:32:47 -0600, Ignoramus5111
wrote:

On 2010-01-07, Larry Jaques novalidaddress@di wrote:
On Wed, 06 Jan 2010 14:15:20 -0600, the infamous Ignoramus5111
scrawled the following:

If I run a motor from a VFD at a higher than 60 Hz frequency, it would
decrease its output power. This is all fine, but I would like to see
some graphs as to how much it loses its power if I overspeed it by 2
times (such as running a 1800 RPM motor at 3600 RPM). Does anyone have
a such a graph?

Holy ****, Ig. Got flak jackets and armored viewing ports?

P.S: You're trolling, aren't you? Shameful.


Do you think that a 1800 RPM motor would self destruct at 3600 RPM?

i

A failure is possible both mechanically and electrically - Inverter
Duty motors have to handle much higher voltage spikes coming from the
inverter than they would ever see from mains power, and you can easily
flashover and short or ground the windings on an old motor. Or to put
it in simpler terms, the Magic Smoke escapes.

This is why you do not run a very expensive or irreplaceable old
motor on a VFD. Stuff like the purpose built motors that are a part
of the machine casting (old Bridgeport vertical mills, some Shapers,
etc.) that will cost you a bloody fortune to tear the motor out and
get it rebuilt, and FWIH many of the old ones are not inverter rated.

You use the VFD on inverter duty rated motors, or on something that
uses a cheap and easily replaced motor like 1 HP 56-C mount. You can
get a new motor for pennies that are inverter rated if that old one
goes kablooey.

I know it goes against the r.c.m credo, but Real Men do in fact read
the (friendly) manual first. At least a quick once-over.

-- Bruce --