Got a TECO N3 VFD to power the spindle motor for my old Hurco KMB1. I
was using a static phase converter on this machine, but the
acceleration ramp up to speed was excessive. The TECO is a 1ph in 3ph
out, and seems to work fine. I have it's I/O configured to accept the
Hurco's FWD/REV signals, and it outputs overload to the Hurco
control. Fine so far, but the braking from full RPM to zero is not as
quick as I might like.

I was hoping to not have to rely on the air operated mechanical
spindle brake, but with the N3's DC injection braking set to max., the
spindle takes ~ 3 seconds to stop without the mechanical brake. I
purchased the optional braking resistor, but it's not clear from the
manual if this really enhances braking over DC injection, or if it's
really more for situations like putting a constant drag on a play out
reel, or slowing a large inertia of some sort. Normally this machine
uses the mechanical brake for stopping at the bottom of a tapping
cycle, before reversing.

Max RPM is the other question. The motor is a 1800 rpm, but could be
dialed up to 3600 at 120 hz. This would save having to crank the vary-
speed belt drive up for smaller end mills, but if it's going to kill
the motor bearings I'm not going to try it. I did run it up to 2400
rpm for a few minutes and it seemed smooth and quiet. I'm guessing the
bearings on 1800 rpm and 3600 rpm motors are the same, and since it's
a 3ph motor there are no windings to throw. Also the Hurco control
board has an analog speed command which I could wire up. This could
be kinda nice, as the program could then control the spindle speed as
coded, instead or the present operator adjust. Setting the vary-drive
to a fixed speed, say 2500 spindle rpm @ 1800 motor rpm would allow me
to cover 500 to 5000 rpm using only the VFD. So far the VFD has not
spiked the 24 year old motor's insulation..

oldjag wrote:

Got a TECO N3 VFD to power the spindle motor for my old Hurco KMB1. I
was using a static phase converter on this machine, but the
acceleration ramp up to speed was excessive. The TECO is a 1ph in 3ph
out, and seems to work fine. I have it's I/O configured to accept the
Hurco's FWD/REV signals, and it outputs overload to the Hurco
control. Fine so far, but the braking from full RPM to zero is not as
quick as I might like.

I was hoping to not have to rely on the air operated mechanical
spindle brake, but with the N3's DC injection braking set to max., the
spindle takes ~ 3 seconds to stop without the mechanical brake. I
purchased the optional braking resistor, but it's not clear from the
manual if this really enhances braking over DC injection, or if it's
really more for situations like putting a constant drag on a play out
reel, or slowing a large inertia of some sort. Normally this machine
uses the mechanical brake for stopping at the bottom of a tapping
cycle, before reversing.


If I'm reading this right, you bought a new VFD to run your spindle motor.

You have the resistor so hook it up and try it. It is for regenerative braking where the
motor is used as a generator and the load is sinked there.

DC injection, I thought was to stop a motor that wasn't carrying a large inertial load.
Like in something like a tool changer arm or a tool magazine. At least that is where I've
seen DC injection used.

Wes

....
If I'm reading this right, you bought a new VFD to run your spindle motor.

You have the resistor so hook it up and try it. It is for regenerative braking where the
motor is used as a generator and the load is sinked there.

DC injection, I thought was to stop a motor that wasn't carrying a large inertial load.
Like in something like a tool changer arm or a tool magazine. At least that is where I've
seen DC injection used.


Just one data point. I added a brake rsistor on my Hitachi VFD spindle
for my Excello. Very similar mill. I was able to improve stop time
from 6 seconds to 0.3 seconds. That is from 3600 motor RPM.

Karl

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?

On Feb 21, 6:49*am, Karl Townsend
wrote:
...

If I'm reading this right, you bought a new VFD to run your spindle motor.

oldjag wrote:
Got a TECO N3 VFD to power the spindle motor for my old Hurco KMB1. I
was using a static phase converter on this machine, but the
acceleration ramp up to speed was excessive. The TECO is a 1ph in 3ph
out, and seems to work fine. I have it's I/O configured to accept the
Hurco's FWD/REV signals, and it outputs overload to the Hurco
control. Fine so far, but the braking from full RPM to zero is not as
quick as I might like.

I was hoping to not have to rely on the air operated mechanical
spindle brake, but with the N3's DC injection braking set to max., the
spindle takes ~ 3 seconds to stop without the mechanical brake.
The braking resistor is designed to absorb the
energy taken from the motor by the VFD. When the
VFD resuces frequency, energy is returned to the
DC bus of the VFD, and the voltage rises. When it
hits about 380 - 400 V the braking resistor is
turned on in pulses to get rid of the energy.
You can set the frequency ramp-down rate of the
VFD, and get any level of slowing you want, up to
the point that the braking resistor, when on all
the time can't absorb the energy, and then the
drive will fault on an overvoltage condition. You
need to set the slow-down time longer than when
you get the fault. I have my Bridgeport 1J set
for a 1 Sec ramp from current speed down to 10 Hz,
at which time the DC injection turns on to
complete the stop.

Jon

oldjag wrote:
....
Any thoughts on exceeding the base RPM, ie. 2X on a 1800 rpm motor?

I have an 1800 rpm motor on my lathe that I run up to 120Hz, no problem
(yet). IIRC, 120 Hz is commonly used on 1800 rpm motors. On my drill
press I run a 3600 rpm motor up to 90 Hz (5400 rpm). The construction
of 1800 & 3600 rpm motors is probably nearly identical. Implying that
an 1800 rpm motor could be run at 5400 rpm. But I don't. It would be a
good experiment. G

Bob

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.""

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

oldjag wrote:
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.
You may need to tell it that the braking resistor
has been installed. Then, you need to specify a
deceleration rate, usually some # of seconds (and
often tenths) to stop.
You may also have to specify what frequency to
switch over to DC braking.

Jon

On 2009-02-22, oldjag wrote:

[ ... ]

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.

That may be.

The resistor is not even getting warm after
several full rpm to zero stops.

Could you measure voltage on the resistor during the stops? i
would guess not.

Guess I gota call Teco's help line
Monday. Any thoughts on exceeding the base RPM, ie. 2X on a 1800 rpm
motor?

I would be a lot happier about that than on a 3600 RPM motor,
since the same rotor is used in many motors of the same size, so it is
likely built to handle 3600 RPM without problems.

Enjoy,
DoN.

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