Analog voltage increases when VFD is connected

[martyscncgarage]

First what kind of machine are we talking about? Pictures please
Second, does it have a transmission? Step Pulleys? What is the spindle speed range of the machine? 0 to ?
Third, POST A FRESH REPORT (F7 Utilities, F7 Create Report)
Screen shot of your Wizard Spindle page

I don't follow your post:
"To get 3000 rpm following the post, i need 108 hz.
To get 640 rpm following the post, the frequency goes down to 108 but, if the frequency is no more 118, means that I will not get the max velocity I want.
In the tests the max velocity at 108 hz is 2750rpms and the intermediate speeds does not match.
Marty, if you can, please post a video with the procedure so I can see if I am making something wrong ?"

The process is straight forward, you won't get it dead nuts.
Let's "assume" your machine's spindle speed range is 0 to 10000 rpm (no transmission, step pulley belt changing etc)
In the SPINDLE section of the Wizard, you set the minimum speed range to 0 and maximum to 10000

You must program the VFD properly. Including motor VAC, amperage, poles, control from terminals etc....
You program the VFD for a minimum frequency for 0 hz
Program the VFD for a Maximum frequency of say 120hz

Get a hand held tachometer so you can check the spindle speed
Go into MDI and do an M3 S5000
Spindle should start rotating. (is it rotating in the proper direction? If not reverse any two motor wires at the VFD)
Check the spindle speed with the hand held tachometer. What does it read? Higher or lower?
Continue increasing the spindle speed with the S word until you hit 10000 (or the high speed). Look at the VFD display, What frequency does it display? THAT is your MAX Frequency for 10K Rpm. Shut down the spindle with an M5, Program the new MAX frequency value.
Test again. Call M3S10000, your spindle should be running at 10000 rpm and your VFD display should match the frequency you programmed (or be pretty close

Now say your initial setting of 120HZ max did not get you to 10000 rpm. Increase the frequency higher until you are allowed to get to your target max RPM. Keep in mind while doing this, you are increasing the S word only to get your spindle actually turning the MAX rpm, so you can read the VFD and record the frequency that gives you the desired RPM. Its not accurate until you program the correct MAX frequency in the VFD to give you the MAX RPM.

Marty

[rflopes3]

Ok Marty, Lets answer your questions first.

My machine is a chinese machine just like the RF45, ZAY-7045...

Spindle Range is 0 to 3000 rpm

Spindle config on the Wizard is NO (rigid tapping), NO for Encoder, 3000 MAx Speed, 1 and 1 for intermediate and low range ratios (pretty default I guess)

What I mean by "following the post" is following cnckeith post about tunning the speeds.

Yes it have gears and on high range the spindle/motor ratio is 0.883 to 1, so when my motor is at 1700rpm my spindle is at 1500rpm (approx).

Now I will describe my procedure to you.

I have set my VFD to 120hz (max) and 0hz (min)

Got the spindle override at minimum and spindle on manual mode

Start the spindle, it's runnig clockwise, got my tachometer on the spindle and start to increase spindle override until I got 3000rpm on the tachometer. Check the VFD output Hz and that was 118hz. So i set my max Hz on the VFD to 118.

Put spindle override at 100% and spindle on auto and opened the MDI.

Put M3 S500 and got 675rpm (Not OK).
Put M3 S3000 and got 3010 rpm (OK)
Put M3 S1000 and got 1130 rpm (not ok)

[tblough]

And if the frequency at 10,000 RPM turns out to be (for example) 112 Hz, then 5000 RPM will occur around half that frequency, or around 66 Hz. Similarly, 1000 RPM, if you can reach that low, would occur at approximately 1/10 the maximum near 11 Hz.

Unless your VFD has span and offset adjustments for the input voltage, then you will have to pick one speed/frequency point to be "exact" and the rest will be higher or lower than the requested spindle speed.

[martyscncgarage]

And if the frequency at 10,000 RPM turns out to be (for example) 112 Hz, then 5000 RPM will occur around half that frequency, or around 66 Hz. Similarly, 1000 RPM, if you can reach that low, would occur at approximately 1/10 the maximum near 11 Hz.

Unless your VFD has span and offset adjustments for the input voltage, then you will have to pick one speed/frequency point to be "exact" and the rest will be higher or lower than the requested spindle speed.

Correct! As Tom points out, you will not have EXACT speeds across the VFD's range. You might see some VFD's have "patterns" these will vary the speeds.
I generally try to get the low end as close as I can get an not worry much about the top end, because that's where you do most of your threading.

Marty

[rflopes3]

Makes sense.

Thanks for all you guys for the help e patience.

And once more Marty, I cannot thank you enough .

[martyscncgarage]

Makes sense.

Thanks for all you guys for the help e patience.

And once more Marty, I cannot thank you enough .

WE collectively try and help each other, there are lots of users that try to help each other out. I am glad to see them active on these forums for the benefit of sharing their thoughts and ideas with other users. We are just making suggestions given the information we are provided. We respond to what we feel we are reasonably comfortable answering.

Centroid builds quality hardware and works very hard on the software. Good practice in implementing then is our (as the user's) responsibility.
So many different varienties of axis drives/motors, spindle drives, VFD's etc. its very difficult to help on them unless we have SOME direct experience with them. The manufacturer support group of those pieces of equipment is our best resource. Sometimes some parts just don't play well together.

Good luck with your build. Be sure to post a video of it cutting and pan to the CNC12 display and post in the success stories forum! That is the thanks all users can give back!

[kevincnc]

Hi again everyone, I thought I would post a little follow-up in hopes that it might help someone in the future. Here are the VFD's I tried:
1) Teco- problems described at the beginning of this thread.
2) Yaskawa- more problems described in thread, no luck fixing it.
3) Huanyang- This was an old drive that I had laying around, and spindle speed was stable with this one. That was encouraging because it made me think that it wasn't a noise problem, but just two VFD's that were bad. However it was an old V/F only drive, so not good enough for my machine. I decided to try another cheap Chinese one figuring I'd use it on something else if it didn't work.
4) Lapond SVD-PS- This drive had the problem of making the analog voltage increase when connected to the Acorn, and also not very stable. The manual suggested connecting a .022mfd capacitor across the analog signal to reduce noise. I tried that, and it just seemed to kill the voltage signal completely. Now I think that since I was running it very slow when I tried it, it may have just dropped the voltage a little and looked like it killed it.

I was able to adjust the analog voltage offset on the Lapond to make it close enough on RPM to work with rigid tapping, but not great accuracy across the range, and RPM would fluctuate up to 10 RPM depending on the day.

The good news- A .1mfd CAPACITOR FIXED BOTH PROBLEMS! Not only did it fix the stability, it made the voltage correct across the range. Here is a video showing how it looked without the capacitor. This was not nearly as bad as it would be some days.


Here is the capacitor that fixed it-

This is what it look like with the capacitor, and you can see how much it dropped the frequency. That's because the voltage was too high without the capacitor.


I will say that this drive makes the motor a little noisier than the others but has incredible low speed torque. It's much better than the others, and they are all 3HP. The only thing I don't like is that it has a little overshoot when it reaches set speed, but drops to the proper RPM pretty quickly so it doesn't seem to matter.

Thanks a bunch to you guys for the capacitor tip, in my case it worked perfectly. I didn't even have to tweak the max frequency for it to be very close at all RPM's.

Kevin

[martyscncgarage]

Interesting. Thanks for sharing the info Kevin.
Especially the bit about the capacitor.
Marty

[rflopes3]

THanks kevin. About the capacitor, I know that they are .1mf but they have a voltage specification. Is that important ? Whats the voltage specification on yours?

[kevincnc]

THanks kevin. About the capacitor, I know that they are .1mf but they have a voltage specification. Is that important ? Whats the voltage specification on yours?

That one is 50V, but I would think anything over 10 would work. I got 50 of them on amazon for $2.