After installing the brake resistor and messing with my 1 HP drive on
the Bridgeport...

Here's something I do not understand.

Depending on frequency and belt ratio, the drive would have a
differing minimum stopping time. No surprise here, since stopping a
motor involves dissipation of its kinetic energy, which depends on the
RPM of the whole rotating mass. The more RPM, the more energy, the
longer it takes to dissipate.

That's kind of obvious.

But my VFD only offers a fixed time braking option, I can set a "stop
time" regardless of run frequency or belt ratio.

If so... Why does my drive (as are other drives that I have seen) does
not offer a braking option that would amount to "just dissipate as
much energy as it can without causing overvoltage"?

This VFD can stop my mill, at low frequency and RPM, in a small
fraction of a second.

At higher RPM, it takes longer.

What is so difficult about writing software that would take it into
account?

The provided function to enable overvoltage protection, just does not
seem to be working.

There must be something that I am missing.
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On Tue, 02 Sep 2008 22:42:30 -0500, Ignoramus2176
wrote:

After installing the brake resistor and messing with my 1 HP drive on
the Bridgeport...

Here's something I do not understand.

Depending on frequency and belt ratio, the drive would have a
differing minimum stopping time. No surprise here, since stopping a
motor involves dissipation of its kinetic energy, which depends on the
RPM of the whole rotating mass. The more RPM, the more energy, the
longer it takes to dissipate.

That's kind of obvious.

But my VFD only offers a fixed time braking option, I can set a "stop
time" regardless of run frequency or belt ratio.

If so... Why does my drive (as are other drives that I have seen) does
not offer a braking option that would amount to "just dissipate as
much energy as it can without causing overvoltage"?

This VFD can stop my mill, at low frequency and RPM, in a small
fraction of a second.

At higher RPM, it takes longer.

What is so difficult about writing software that would take it into
account?

The provided function to enable overvoltage protection, just does not
seem to be working.

There must be something that I am missing.


No..apparently you have a "dumb" VFD

There are others out there that are far far more able.

Did yours ask what max amps your motor draw? Does it offer "autotune"?

There are VFDs..and VFDs

On the other hand..you are unlikely to be tapping at 3000 rpm either
so if it takes .5 seconds longer to stop..so what?

Dont over complicate things


Gunner

"Obama, raises taxes and kills babies. Sarah Palin - raises babies
and kills taxes." Pyotr Flipivich

On 2008-09-03, Gunner Asch wrote:
On Tue, 02 Sep 2008 22:42:30 -0500, Ignoramus2176
wrote:

After installing the brake resistor and messing with my 1 HP drive on
the Bridgeport...

Here's something I do not understand.

Depending on frequency and belt ratio, the drive would have a
differing minimum stopping time. No surprise here, since stopping a
motor involves dissipation of its kinetic energy, which depends on the
RPM of the whole rotating mass. The more RPM, the more energy, the
longer it takes to dissipate.

That's kind of obvious.

But my VFD only offers a fixed time braking option, I can set a "stop
time" regardless of run frequency or belt ratio.

If so... Why does my drive (as are other drives that I have seen) does
not offer a braking option that would amount to "just dissipate as
much energy as it can without causing overvoltage"?

This VFD can stop my mill, at low frequency and RPM, in a small
fraction of a second.

At higher RPM, it takes longer.

What is so difficult about writing software that would take it into
account?

The provided function to enable overvoltage protection, just does not
seem to be working.

There must be something that I am missing.


No..apparently you have a "dumb" VFD

There are others out there that are far far more able.

I will try to find out if there are sm,arter ones, just for the kicks
I will call drives warehouse.

Did yours ask what max amps your motor draw? Does it offer "autotune"?

I could enter that stuff, yes. But it is optional.

There are VFDs..and VFDs

On the other hand..you are unlikely to be tapping at 3000 rpm either
so if it takes .5 seconds longer to stop..so what?

Dont over complicate things

I just think that it is bad, to be sub-optimal like this.

Anyway, I know by heart by now that it is parameter 1-10 and it is
easy to change. So I can change it to be 0.3 sec for tapping and 1 sec
for everything else.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
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