On 2008-09-03, Gunner Asch wrote:
On Tue, 02 Sep 2008 20:07:37 -0500, Ignoramus2176
wrote:

I wired the resistor.

At more or less the highest RPM, the mill can be stopped in 0.9
seconds. As I found out, I originally wired it for 3 seconds stopping
time. So this is an improvement (3.3 times less).

wired? Or programmed?

programmed, sorry.

I am very happy.

I wish that the VFD reduced braking efforts, if it detects
overvoltage, instead of tripping on overvoltage. This is really not
too smart on the part of the VFD, unless I missed something. If it
could do that, then the mill would stop almost instantly at low RPM,
and longer at higher RPM.

It should do that now. What vfd do you have and how much DC braking
have you programmed it for?

I have a Delta S1 VFD. Manuals are he

http://igor.chudov.com/manuals/Delta-S1-VFD/

I have not yet used DC braking, but I believe that it is for something
else (like fans in a windy tunnel or something). Maybe I am wrong, the
drive has it etc.

i

Gunner


i

On 2008-09-02, Mark Rand wrote:
On Tue, 02 Sep 2008 15:29:49 -0500, Ignoramus2176
wrote:


This is very encouraging. I think that what I will do after installing
the resistor, is try to take the stopping time as low as possible, at
highest RPM. Then I will back out just a bit. Almost instant stop, is a
very convenient thing.

i


Practically, the minimum braking time for the motor-VFD combination (with
suitable braking resistor) will be approximately twice the minimum starting
time that the VFD can drive the motor at. For the simple reason that it's
either going to be limited by motor torque or VFD capacity on the way down in
exactly the same way that it is on the way up.


regards
Mark Rand
RTFM

"I am for doing good to the poor, but I differ in opinion of the
means. I think the best way of doing good to the poor, is not
making them easy in poverty, but leading or driving them out of
it. In my youth I travelled much, and I observed in different
countries, that the more public provisions were made for the
poor the less they provided for themselves, and of course became
poorer. And, on the contrary, the less was done for them, the
more they did for themselves, and became richer." -- Benjamin
Franklin, /The Encouragement of Idleness/, 1766

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