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

Probably not, but I'd hate to find out the hard way. Most inverter
duty motors have a max rpm listed on the nameplate, which I like to
see to know the safe range. I've used plenty with max rpm about 4300.
No way I'd run 120 Hz on a 3600 rpm motor, though. You might look on
line at the motor manufacturer's web site for max speed data.

Also, consider that since the horsepower stays constant above 60 Hz,
the torque is dropping proportionally to the speed increase.

I was told of the aftermath of a sudden stoppage on a slow speed 2300
V. 100 hp. pump motor in a plant I worked in. Part of the plant lore.
Apparently something really big dropped into the impeller. This was
on a production scale caustic evaporator circulation pump. The motor
(3' in diameter IIRC) tore off its foundation and wrapped the pump
shaft into a corkscrew as it rolled across the ground floor of the
plant, coming to rest outside in a ditch. Since it would have dumped
the whole evaporator of hot caustic, glad I wasn't around to see it.
Throwing the armature windings would cause a similar sudden stoppage.

Pete Keillor

Pete Keillor