problems with the inverter of the lathe

[squirrel]

Hi, this is the adress where you can see what my problem looks like: Tania_VB_MVI_7784.MOV

Hello everybody!

My lathe performs well for weights till approx 50 -60 kg, pretty well balanced pieces and size till 75 - 80 cm width.

Some days ago I put on my lathe a 180 cm wide plate, pretty balanced and with some glued wood on it. I need to turn a 160 cm wide ring (diameter ring 4 cm). Weight 75 - 90 kg
But:
- the lathe does not want to turn faster than 50 - 60 rpm before the system brakes down
- I can stop the lathe with my smallest gouge if I want to do that and with almost no use of any power

The lathe performs well if I put smaller items on it again and the 3 HP motor and shaft is capable to keep and turn logs till 500 - 600 kg (or it should but not in my case)


- The invertor mark Parker AC integrator - 690 + series, serial number 3650734500100300841 bs 041 fw5v6 is doing his job not well, I presume

Do you think
- it has to be reprogrammed
- I need a more simpler invertor
- it is better to have an invertor who can handle a motor of 5 HP and to use it on my 3 HP lathe
- something else?

As there are a lot of technicians among you and also engineers, your advice can be of some help, I hope.

Best regards - Squirrel

 

[squirrel]

Problems with the invertor of my lathe: CORRECTION!

Hi,

sorry the link to youtube is wrong. This is the right link

http://youtu.be/iirNnqfo3Fc


Thanks - Squirrel.

 

[Dennis J Gooding]

What is the lathe that you are using? Does it have have a step pulley arrangement to select speed/torque ranges; if so, are you using the lowest speed range?

Dennis

 

[MichaelMouse]

Note that Europe normally has 3-phase power available, thus the integrator may be set for various inputs. http://www.ssddrives.com/usa/Products/AcDrives/690-series.php

Greatest mechanical advantage, as noted from smallest sheave on motor to largest on spindle, if available. Note the overload protection in the controller itself.

Only suggestion available, without knowing the wiring and output, is to suggest you act as the starting capacitor acts on a capacitor start motor. Start the rotation by hand, then cut in the power.

 

[Bill Boehme]

My comments are marked in red within your quote below:

Hi, this is the adress where you can see what my problem looks like: Tania_VB_MVI_7784.MOV

Hello everybody!

My lathe performs well for weights till approx 50 -60 kg, pretty well balanced pieces and size till 75 - 80 cm width.

Some days ago I put on my lathe a 180 cm wide plate, pretty balanced and with some glued wood on it. I need to turn a 160 cm wide ring (diameter ring 4 cm). Weight 75 - 90 kg
But:
- the lathe does not want to turn faster than 50 - 60 rpm before the system brakes down
- I can stop the lathe with my smallest gouge if I want to do that and with almost no use of any power

The lathe performs well if I put smaller items on it again and the 3 HP motor and shaft is capable to keep and turn logs till 500 - 600 kg (or it should but not in my case)


- The invertor mark Parker AC integrator - 690 + series, serial number 3650734500100300841 bs 041 fw5v6 is doing his job not well, I presume

Do you think
- it has to be reprogrammed No, unless there was some sort of power surge or lightning strike nearby that might have damaged equipment plugged ino the power line at the time.
- I need a more simpler invertor No, your inverter is properly matched to the motor and drive transmission.
- it is better to have an invertor who can handle a motor of 5 HP and to use it on my 3 HP lathe No, the inverter and motor should be sized to work together.
- something else? Yes, after reading your above comments and then seeing your video, I have a possible cause of the problem in mind.

As there are a lot of technicians among you and also engineers, your advice can be of some help, I hope. Yes, there are several engineers who participate regularly on this forum. I am a retired engineer and my area of expertise included stability design and analysis of feedback control systems -- in other words, your lathe would fall within that category.

I have a couple questions -

• If your lathe hads more than one speed range -- in other words a low speed range and a high speed range, was the lathe in the high speed range?
  
• Does the lathe speed seem to surge faster and slower when it is having the problem with a larger turning?
  

If the answer to both of the above is yes, that is a very strong indicator that there is a control system instability caused by the object being turned having a very large moment of inertia -- in other words a large mass located a long distance from the axis of rotation. I can tell from your description and from seeing the video that the turning does have a very large moment of inertia. If you had the drive belt in the high speed range, the load being reflected back to the motor and speed sensing circuitry is creating a system response lag time that beyond the capability of the system to maintain stable operation. Speed surging would be an indicator of lack of stability control. The cure is to switch the lathe's drive belt to the low speed range. If the lathe drive belt is already in the low speed range then it is possible that the lathe manufacturer might be able to provide you with alternate "PID" parameters for stable operation and tell you how to reprogram those values into the controller. This alternate solution is a long shot and might not work satisfactorily in all cases.

Even if the answer to both of the above question is "no", it is still possible that the problem is related to instability due to the turning having a very large moment of inertia. There is a possibility that the load that you are attempting to turn can't be stabilized.

My money is on the cause of the problem being that the drive belt is set to the high speed range. Some of the better controllers have load inertia sensing capability and go into a "safe" mode of operation because an unstable system can go divergent very rapidly (in layman's terms, "go out of control and surge fast enough for the turning to start breaking apart and throwing chunks of wood").

Best regards - Squirrel

Hope this helps.

 

[squirrel]

Oefff ... a lot of things .... thank you all of you!
I'll give this notes to the people who try to help me.

My lathe is a VB36 - 3 HP. Is (normally able to turn 500 - 600 kg ).
We have 3-phase and I have and the motor of the lathe is 3 phase but it is monophase 220 v at the end - has something to do with haveing more power, I heard.
It was turning on the pulley for heavy loads (50 - 500 rpm)
I choose the ' slow starting' instead of the fast starting program.
I helped the lathe to start with my hand.
When I try to make it turn faster than aproximatively 75 - 100 rpm the lathe falls out.
At the speed where the motor does not fall out you can hear the motor: give power, give no power - give power and so on and so on - which makes it impossible to TURN. The only thing I can do is to keep a very sharp gouge against the wood without ANY touch - just a very fine cut is possible.
It is not the speed who is going fast and slow , it is power - no power and very very weak ... .

For smaller items it works perfect and a couple of days ago I put on a board with the ax on 30 cm from one side and 100 cm from the other side and the board was only 1 inch thick and it flow around - constant speed, without problem.

Don't you think that the problem will be solved if I place an invertor which can handle a 5 HP motor on the lathe who has a 3 HP motor?

Thanks - Squirrel

 

[Bill Boehme]

... My lathe is a VB36 - 3 HP. Is (normally able to turn 500 - 600 kg ).
We have 3-phase and I have and the motor of the lathe is 3 phase but it is monophase 220 v at the end - has something to do with haveing more power, I heard.
It was turning on the pulley for heavy loads (50 - 500 rpm)
I choose the ' slow starting' instead of the fast starting program.
I helped the lathe to start with my hand.
When I try to make it turn faster than aproximatively 75 - 100 rpm the lathe falls out.
At the speed where the motor does not fall out you can hear the motor: give power, give no power - give power and so on and so on - which makes it impossible to TURN. The only thing I can do is to keep a very sharp gouge against the wood without ANY touch - just a very fine cut is possible.
It is not the speed who is going fast and slow , it is power - no power and very very weak ... .

For smaller items it works perfect and a couple of days ago I put on a board with the ax on 30 cm from one side and 100 cm from the other side and the board was only 1 inch thick and it flow around - constant speed, without problem.

Don't you think that the problem will be solved if I place an invertor which can handle a 5 HP motor on the lathe who has a 3 HP motor?

Thanks - Squirrel

The additional information seems to confirm my suspicion that the problem is due to control system instability.

Single phase power is not better than three phase, but for the inverter it may not matter which you use.

A larger inverter is not the solution because the problem is the motor -- unless the inverter is undersized and operating in the variable torque mode rather than the constant torque mode.

 

[squirrel]

Hello!

if it was YOUR lathe and YOUR problem what would you do?
- first look if the inverter is not undersized and operating in the variable torque mode rather than the constant torque mode.
- second try this 'PID parameters' (what does this mean?)
- third ..... put a new motor in??? A heavier one???

question: how is it possible that so many VB36 are performing well and mine not? Just bad luck and having a motor which does not work well? Then it could be sufficient to change the motor for the same kind of motor and inverter , no?
Tobias Kaye turned the same size and much much wider pieces for years .... much heavier too ... without problem ... .

Thanks again - Squirrel.

 

[MichaelMouse]

Confused. Whence the "inverter" into this discussion? I thought you had a 3 phase (input), variable frequency (output) power supply.

Assuming the word choice to be incorrect, I would agree that your problem stems from the feedback control circuitry built into the converter. Recheck your wiring in and output settings, which you indicate is 240V variable Hz. Then look for compensation circuitry which you can tune. Should be there somewhere, because one size never fits all circumstances, and a bit of field adjustment is often the answer to problems like yours.

Since it is a SAFETY feature, I'd talk to the technicians who service the converter before I started modifying the parameters.

I wouldn't get a larger controller, though I might borrow someone else's of equal specifications to see if it would do the job.

 

[squirrel]

Michael,

in the handbook there is written that the motor is three phase and the supply voltage is 220/240 volt, 50 or 60 cycles, single phase.
I have 50 hz here in the house and 220 v as well.
My other machines run on 380 v but NOT the lathe.


Seems pretty difficult what has to be done ... I will as well, give this knowledge to some more experienced guys who try to help me ...
Don't know what it is: inverter ... motor ... both ... . But at the end there must be a solution.

Thank you - Squirrel.

 

[hockenbery]

When I get stuck I call the company that makes or sells the lathe
The companies I have dealt with have seen all the common problems
And have they taken me step by step in identifying the problem.

You have a good quality machine.
Al

 

[squirrel]

Hi,

1. the company is settled in UK and I am in Belgium: that means over the water.
2. the company is sold ...

If this was the easiest, BEST and cheapest solution: just call the company - you can be sure I would do that! But I'm afraid that for the moment it would not be of a lot of help ...

Squirrel

 

[Bill Boehme]

Confused. Whence the "inverter" into this discussion? I thought you had a 3 phase (input), variable frequency (output) power supply.

The term inverter is the broader term that covers electronic devices that convert supply power (single or three phase) into three phase power to the motor that may or may not have adjustable frequency capability. There may also be a number of other features depending on the complexity (translation: cost) of the inverter. There are also single phase output variable frequency inverters used for small air handlers where the power requirement is fractional HP and the starting torque is essentially zero. Terms like VFD are basically a subset of the larger category. I know that the term "inverter" sounds like a misapplication, but like a lot of terms, it has its roots in the evolution of devices that convert single phase to three phase.

Hello!

if it was YOUR lathe and YOUR problem what would you do?
- first look if the inverter is not undersized and operating in the variable torque mode rather than the constant torque mode.
- second try this 'PID parameters' (what does this mean?)
- third ..... put a new motor in??? A heavier one???

question: how is it possible that so many VB36 are performing well and mine not? Just bad luck and having a motor which does not work well? Then it could be sufficient to change the motor for the same kind of motor and inverter , no?
Tobias Kaye turned the same size and much much wider pieces for years .... much heavier too ... without problem ... .

Thanks again - Squirrel.

Is your inverter or motor different than those on other VB36 machines? If a company was sliding downhill, would they start using components that do not perform to the same specifications as previous machines? Probably not in this case, but it has been known to happen.

Are you saying that the company doesn't provide technical support or that you feel like the distance and language differences are the main barriers? If the latter, persistence usually pays off.

PID stands for Proportional Integral Differential. Those are the three main parameters that are adjusted to match the inverter to the motor and drive train for stable operation. The proportional gain minimizes the steady state error, the integral gain reduces errors that accumulate as a result of variations in load torque or speed, and the differential gain minimizes overshoot when the inverter is correcting for speed errors. During initial set up, these parameters are usually automatically tuned to optimum values based on the characteristics of the motor and of the composite moment of inertia consisting of the rotor, pulleys, spindle and nominal load attached to the spindle. Generally a motor can handle a load moment of inertia that is up to three times that of the rotor without any stability problem.

As I mentioned in a previous post, your controller might be going into a "safe" mode if it is sensing a load moment of inertia that is outside of its capability to safely handle.

It is possible that your controller has had some sort of reset which caused it to revert to a set of default operating parameters. This is the sort of problem that can't be effectively diagnosed by long distance unfortunately.

One other thought: Since the VB36 is a top of the line machine, it is possible that the inverter uses true speed and position feedback on the motor as opposed to lower cost schemes such as sensorless vector or volts/Hertz. If the motor has a cylindrical object mounted on the back side of the shaft, that would be an indication of a feedback device. If it malfunctions, then it would cause a problem with the speed of the motor.

There

Hi,

1. the company is settled in UK and I am in Belgium: that means over the water.
2. the company is sold ...

If this was the easiest, BEST and cheapest solution: just call the company - you can be sure I would do that! But I'm afraid that for the moment it would not be of a lot of help ...

Squirrel

That is a real problem. Surely there must be someone in Belgium who works on these types of inverters.

 

[squirrel]

Thank you all of you, very very much!
I will translate the pages and show them to some 'technical' skilled people here in Belgium.
I know it will take some time and I prefer to take the needed time and to solve it definitively than to go too fast.
Also, I'm working in France during july and august ... I'll tell you if I have solved the problem ... probably in september ... in the meanwhile, I can turn smaller pieces as it does perform well for smaller items.

Bill, You seem to live in a beautifull surrounding, beautifull and peacefull photofraphs and woodturnings too! Have a nice summer - Squirrel.

 

[MichaelMouse]

The term inverter is the broader term that covers electronic devices that convert supply power (single or three phase) into three phase power to the motor that may or may not have adjustable frequency capability.

Clever how words don't mean the same things sometimes. To me an inverter makes AC out of DC. Didn't seem to fit.

 

[Bill Boehme]

In a seemingly unimportant way I suppose that one could justify the term inverter. The AC input power gets converted to DC and then the output circuit synthesizes the approximate equivalent of three phase AC, at least as far as the motor is concerned. If you were to view the output from the "inverter" on a scope, it would not be obvious that it was an AC voltage.

 

[ray hampton]

In a seemingly unimportant way I suppose that one could justify the term inverter. The AC input power gets converted to DC and then the output circuit synthesizes the approximate equivalent of three phase AC, at least as far as the motor is concerned. If you were to view the output from the "inverter" on a scope, it would not be obvious that it was an AC voltage.

Bill, if the output from a car coil was fed to a scope, will the scope show a pulsing DC VOLTAGE or a A C voltage ? I will guess that it will show a pulsing dc voltage as high as 30,000 volts

 

[Bill Boehme]

Bill, if the output from a car coil was fed to a scope, will the scope show a pulsing DC VOLTAGE or a A C voltage ? I will guess that it will show a pulsing dc voltage as high as 30,000 volts

It would be a damped sinusoid with a small dc bias voltage.

I don't know what the spark gap breakdown voltage is, but that would be the limiting value.