So, I have a 1 HP Bridgeport on a VFD. The time has come to install a
braking resistor. I had it for a while, but wanted to install the DRO
first. With the DRO, and wiring better organized, installing brake
resistor is more pleasant.

The question is about stopping time.

Right now (without the external brake resistor), I have the mill set
to stop in 1 second. That works at most speeds, except at highest RPM
it trips on overvoltage and then coasts to stop.

Just what can I realistically expect with a brake resistor? Would you
say that I could expect to stop it in 1/2 second at all speeds?

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On Tue, 02 Sep 2008 14:46:57 -0500, Ignoramus2176
wrote:

So, I have a 1 HP Bridgeport on a VFD. The time has come to install a
braking resistor. I had it for a while, but wanted to install the DRO
first. With the DRO, and wiring better organized, installing brake
resistor is more pleasant.

The question is about stopping time.

Right now (without the external brake resistor), I have the mill set
to stop in 1 second. That works at most speeds, except at highest RPM
it trips on overvoltage and then coasts to stop.

Just what can I realistically expect with a brake resistor? Would you
say that I could expect to stop it in 1/2 second at all speeds?

Yes. I tap with my Gorton Mastermill, which has a HEAVY motor (5hp)
and a big spindle.

I can do an "invisible reverse" at speeds up to 5000 rpm. Changes
direction so fast you never see it.

I do have a 5hp VFD and a big breaking resistor. A tubular ceramic
btw.

A braking resistor is essential if you are doing braking, or fast
reverses.

I specialize in OmniTurn CNC lathes, which use a 5hp motor and can do
an invisible reverse at 4000 rpm, and they too have a big braking
resistor.

I have a 3/4hp motor on my Big Delta drill press, with an older
Hitachi VFD..no braking resistor..and it trips if I try to tap with it
at just about any speed.

Some VFDs come with a small internal resister, some with none, some
with no provisions for an external resistor

Gunner,


"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

On 2008-09-02, Gunner Asch wrote:
On Tue, 02 Sep 2008 14:46:57 -0500, Ignoramus2176
wrote:

So, I have a 1 HP Bridgeport on a VFD. The time has come to install a
braking resistor. I had it for a while, but wanted to install the DRO
first. With the DRO, and wiring better organized, installing brake
resistor is more pleasant.

The question is about stopping time.

Right now (without the external brake resistor), I have the mill set
to stop in 1 second. That works at most speeds, except at highest RPM
it trips on overvoltage and then coasts to stop.

Just what can I realistically expect with a brake resistor? Would you
say that I could expect to stop it in 1/2 second at all speeds?

Yes. I tap with my Gorton Mastermill, which has a HEAVY motor (5hp)
and a big spindle.

I can do an "invisible reverse" at speeds up to 5000 rpm. Changes
direction so fast you never see it.

I do have a 5hp VFD and a big breaking resistor. A tubular ceramic
btw.

A braking resistor is essential if you are doing braking, or fast
reverses.

I specialize in OmniTurn CNC lathes, which use a 5hp motor and can do
an invisible reverse at 4000 rpm, and they too have a big braking
resistor.

I have a 3/4hp motor on my Big Delta drill press, with an older
Hitachi VFD..no braking resistor..and it trips if I try to tap with it
at just about any speed.

Some VFDs come with a small internal resister, some with none, some
with no provisions for an external resistor

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

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've just installed the brake resistor on a 5 hp Hitachi VFD going to a four
horse spindle.

Hitachi allows two accel/decel/max speed profiles based on an input. So, I
set up #2 to have a lower max speed and very high decel. This is for CNC
tapping, it stops and reverses on a dime.

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).

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.

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

--
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.
http://improve-usenet.org/

Ignoramus2176 wrote:
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.
Some do. Instead of a fixed ramp time from 0 - set speed, some
also have a ramp rate, in Hz/sec. That would take less time at
the lower speeds. Most of these drives have SCADS of hidden
options that only become obvious on the 10th reading of the manual.

Jon

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?

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?

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

....
Ignoramus2176 wrote:
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.
Some do. Instead of a fixed ramp time from 0 - set speed, some also have
a ramp rate, in Hz/sec. That would take less time at the lower speeds.
Most of these drives have SCADS of hidden options that only become obvious
on the 10th reading of the manual.

Jon

Would you happen to know about the specific case of Hitachi VFDs? My CNC
mill would only stop from top speed in 1.4 secs or trip (9 secs. before
brake) . Takes the same 1.4 secs. from low speed.

I found one "back door", there's a second profile allowed (switched based on
an input) so I set max Hz to 30 and decel time to 0.2; I'm still working a
way to to switch for tapping.

karl

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

--
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.
http://improve-usenet.org/

Brakes are great when there is a problem afoot.
Stopping a machine eating itself up or the like is important.

I really enjoy the function in my 1/2" hammer drill. If it catches
on something - I let go of the trigger and it stops. I don't get
wrapped up in the cord and drill bit.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Ignoramus27629 wrote:
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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