On Sat, 21 Feb 2009 20:12:28 -0800, Gunner Asch
wrote:

On Sat, 21 Feb 2009 17:35:25 -0800 (PST), oldjag
wrote:

On Feb 21, 12:45*pm, Gunner Asch wrote:
On Fri, 20 Feb 2009 21:05:54 -0800 (PST), oldjag

wrote:
I
purchased the optional braking resistor, but it's not clear from the
manual if this really enhances braking over DC injection,

The braking resistor sucks up the generated hysterisis currents ...IE
the load the various turning bits has when trying to stop it quickly.

Yes..its way important when trying to stop quickly.

My Gorton Mastermill, with its BIG spindle and 5 hp motor will stop in
under 1 second from *3000 rpm when I hit the stop button. *5hp PC3 VFD
and running from 220vt single phase, with a 200 watt ceramic braking
resistor @ 140 ohms.

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary
that Roosevelt would be remembered as a great president, "maybe even
alongside Washington and Lincoln," opining that Roosevelt "had every
quality that morons esteem in their heroes.""

I installed the 250 watt 60 ohm resistor as per the manual. It does
not seem to be adding to the brake torque, ie the decell time is the
same. I suspect some kind of translation error or omission in the
manual that is leaving out a parameter needed to enable the resistor
braking correctly. The resistor is not even getting warm after
several full rpm to zero stops. Guess I gota call Teco's help line
Monday. Any thoughts on exceeding the base RPM, ie. 2X on a 1800 rpm
motor?


Id not go over 2x the base RPM. Some motors can take 3 or 4x...but
they are going to be screaming!! and its got to be hard on the bearings

Check out the "Decell time" settings, often more than 2 of them, and how
the various Decel times get activated. Some need Stop, others need an
absense of Run and so forth.

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary
that Roosevelt would be remembered as a great president, "maybe even
alongside Washington and Lincoln," opining that Roosevelt "had every
quality that morons esteem in their heroes.""

Ditto on the 2X, and that's on a 4 pole motor. I've also installed
inverter duty motors with max speeds on the nameplate of only 2700
rpm, so a 90 Hz limit. Most are twice that for 180 Hz, or 5400 rpm.

I've never seen a rotor expand from overspeed and don't want to.

Pete Keillor