Selecting a VFD for a Harrison lathe.

[Pete RimmerParticipant @peterimmer30576]

Posted by Daniel Grant on 04/01/2019 17:26:59:

Here’s a couple of pictures from the ‘manual’. Not the most thorough document I’m afraid.

Pics are illegible Daniel. Do you have a scanner? If not and if you're taking them with your phone try an app called CamScanner – it's fantastic at cleaning up documents, can output to JPG or PDF.

[SillyOldDufferModerator @sillyoldduffer]

Have you got an AT1 or an AT4? ( or even an AT2 or AT3 ) Should be a label on the back. I guess you have an AT1 which is the ordinary one, it's the AT4 model that does 220 to 380V (according to the advert).

The instructions are too blurry to read properly – can you zoom in, perhaps 4 pics?

What I can see suggests the instructions cover 4 different VFDs from the AT family, although similar not identical. Also, the current maximum looks to be defaulted to 3000mA, which may be too low for your motor.

Dave

Edited By SillyOldDuffer on 04/01/2019 20:42:55

[Daniel GrantParticipant @danielgrant15006]

The model is an AT4, but the motor has to be converted to 220v to run. Well spotted on the 3000ma max current Dave, that could well be what’s tripping it. I’ll try changing it tomorrow.

Struggling to get the images uploaded after using camscanner, I’ll try to get some clearer pictures.

[Daniel GrantParticipant @danielgrant15006]

No luck with the current limit, the preset value wasn’t actually 3,000 mA as indicated in the manual but 15,000 mA. 

Edited By Daniel Grant on 05/01/2019 10:16:38

[Daniel GrantParticipant @danielgrant15006]

Those images still aren’t really clear enough, I’ll try and sort out a link to a higher res image.

[John HaineParticipant @johnhaine32865]

What speed setting are you starting at? Try setting the speed to zero, switch on, then slowly increase? May minimise the inrush current.

[Daniel GrantParticipant @danielgrant15006]

I have tried both starting at 50Hz and 0Hz then ramping it up, if I go really slowly I can make it up to 5Hz, but any more and it brings up the "Short Circuit / Current Protection" Error. When it's running at 5Hz it sounds really unhealthy.

Below are 2 links to better copies of the document that came with the VFD.

https://drive.google.com/open?id=1xtYxfrR5KKBleoASucNfbk-hPAjYU7U0

https://drive.google.com/open?id=18n3MvYKNO6jzCumfbEpYmpHxiQDFrnMi

[Mike PooleParticipant @mikepoole82104]

What settings do you have for P21 P24 P34? What is the RPM of the motor and the FLC(full load current) at 220V?

Mike

[John HaineParticipant @johnhaine32865]

Ah. First, just to check, you have the 3 phase wires connected one to each of the vertical link bars in your photo?

Second, given it is sounding unhealthy, it is possible that actually one of the windings is connected backwards though the markings on the ends in your photo look right. 3 phase windings have mutual inductive coupling between them and it is important that all these couple in the same sense otherwise the load gets imbalanced and it might account for the high current. This has been covered in a couple of other threads here.

When you say "sounds unhealthy", what do you mean? My little 1//4 hp 3ph motor driving the Unimat makes a squeaky sound at low speed, but runs perfectly quiet once running at 100 rpm or so.

[Daniel GrantParticipant @danielgrant15006]

The motor is connected to the VFD with U,V and W going to the correct positions, the first picture was with the wires removed.

 

Mike – P21 was set to 2800, the motor is supposed to do 1420 RPM so I changed it accordingly.

P24 – 3.0 Seconds

P34 – Currently set to 10Hz/S. I haven't changed this but it is different from the 25Hz/S in the manual.

 

Below is the plate from the motor and I'm trying to work out how to share a video I took that shows it running up to 6Hz before cutting out. Hopefully you'll be able to hear what I mean.

Thanks again for all the help.

Edited By Daniel Grant on 05/01/2019 15:13:25

[Daniel GrantParticipant @danielgrant15006]

Here's a link to the video of the motor turning.

**LINK**

[John RuddParticipant @johnrudd16576]

I'd suggest trying your vfd on the drill machine you got too….would rule out a possible motor problem if the drill runs ok on the vfd….that big motor you have there sounds sick/poorly…..

[John HaineParticipant @johnhaine32865]

The motor sounds like something is binding. Can you feel anything when you rotate it by hand? May be duff bearings, or perhaps some swarf in the air gap between rotor and stator. I noticed that the data plate thoughtfully gave the bearing type (6206ZZ). If you can feel something catching when you rotate by hand, nothing to be lost by dismantling it if free.

[Pete RimmerParticipant @peterimmer30576]

Sounds like it's cogging badly. Either a parameter problem or the VFD is just faulty IMHO.

Edited By Pete Rimmer on 05/01/2019 17:20:08

[not done it yetParticipant @notdoneityet]

Or try runing it in star?

[peak4Participant @peak4]

Posted by Daniel Grant on 04/01/2019 21:52:21:

The model is an AT4, but the motor has to be converted to 220v to run. Well spotted on the 3000ma max current Dave, that could well be what’s tripping it. I’ll try changing it tomorrow.

Struggling to get the images uploaded after using camscanner, I’ll try to get some clearer pictures.

 

Well as I read it, on Page 2 of your "manual", assuming your converter really is an AT4. and not a mislabelled AT1, then the motor should be wired 380-420 in star config, not 220-240 delta.

As mentioned above, try it on the other motor, also wired as 420v star and see how it works with that.

The motor sounds very much like one of mine did when I connected it to a dodgy inverter, where one phase was faulty. Measuring the output voltage with a meter was misleading, as it showed about the same voltage on each of the phases; mine was running in delta with a 240v motor.

It was only when I put the oscilloscope across the terminals that it became obvious that I was a phase down.

Bill

Edited By peak4 on 05/01/2019 18:56:27

[Pete RimmerParticipant @peterimmer30576]

Disconnecting one phase at a time will diagnose that pretty quickly.

[SillyOldDufferModerator @sillyoldduffer]

Posted by peak4 on 05/01/2019 18:54:14:

Posted by Daniel Grant on 04/01/2019 21:52:21:

The model is an AT4, but the motor has to be converted to 220v to run. Well spotted on the 3000ma max current Dave, that could well be what’s tripping it. I’ll try changing it tomorrow.

Struggling to get the images uploaded after using camscanner, I’ll try to get some clearer pictures.

Well as I read it, on Page 2 of your "manual", assuming your converter really is an AT4. and not a mislabelled AT1, then the motor should be wired 380-420 in star config, not 220-240 delta.

As mentioned above, try it on the other motor, also wired as 420v star and see how it works with that.

The motor sounds very much like one of mine did when I connected it to a dodgy inverter, where one phase was faulty. Measuring the output voltage with a meter was misleading, as it showed about the same voltage on each of the phases; mine was running in delta with a 240v motor.

It was only when I put the oscilloscope across the terminals that it became obvious that I was a phase down.

Bill

Edited By peak4 on 05/01/2019 18:56:27

My reading is that the AT4 is like an AT1 except it produces 380V out.

I wonder if connecting a high voltage VFD to a 220V motor would produce the symptoms?

Hypothesis.

Being a box full of electronics with a brain the size of a planet, I don't think a VFD would behave anything like a real three phase supply. Connecting 380V from the national grid into a 220V motor would be obviously wrong – smoke and blown fuses make the fault easy to diagnose! I think a VFD is more subtle.

The VFD generates 380V 3-phase electronically and applies it to the motor. It's power output is limited by the electronics. Everything it does is measured and managed relative to the configuration settings, which include soft safety features intended to protect the electronics.

When a 380V output VFD is connected to a 220V motor the VFD will immediately detect that it's drawing too much current but it keeps going for a short-time because the excess might be normal starting overload. However, if the motor carries on drawing excessive current, the VFD shuts down. That seems to fit the symptoms.

I'm not at all sure how a 220V 3-phase motor would behave when fed excessive volts that are also current limited at source, varying in frequency and – perhaps – trying to follow a software defined starting routine. It seems possible that the motor would run badly for a short time before the VFD decides to cut out.

Daniel : why do you think your AT4 isn't producing 380V 3-phasel? I think the star-delta comment in the manual that implies that refers to the AT1 not the AT4. I agree with Bill – as he said, "try it on the other motor, also wired as 420v star and see how it works with that."

Motor experts: I'm out of my depth and there are safety implications, but is there any reason why a VFD couldn't be tested by wiring 100W filament light-bulbs in star or delta and using them as the load? If the bulbs glow equally, all three phases are working. I'd expect a 220V VFD to light a set of 3 bulbs fully once power is cranked up, and a 380V VFD to burn them very bright. (Wiring this up at 220V is dangerous, 380V more so.)

Dave

[not done it yetParticipant @notdoneityet]

I would not be connecting light bulbs. If one fails, the VFD might go with it (or is the common warning, of not disconnecting the VFD on the outut side, only applicable to inductive loadings?).

[John RuddParticipant @johnrudd16576]

The vfd has 'sensing elements' within the electronics to determine switching points for the windings of the motor….,hence an incandescent load is not suitable….

I would re-iterate my advice earlier, try the vfd on a known good motor to determine if the motor/vfd is at fault or try the motor on a true 3 ph supply if you can….

You need a firm starting point from which to work to 'experiment with the unknown'

[Daniel GrantParticipant @danielgrant15006]

Star connection works! I was sure I read somewhere that these low cost VFDs weren't capable of increasing the voltage, but I guess I was wrong. The link below shows it running on Star and outputting 1490rpm at 50Hz.

Thanks to all for helping me get this sorted, all I need now is a lathe to adapt the original pulley!

**LINK**

[SillyOldDufferModerator @sillyoldduffer]

Posted by Daniel Grant on 06/01/2019 18:13:04:

… I was sure I read somewhere that these low cost VFDs weren't capable of increasing the voltage …

For donkey's years that was true, step-up VFDs existed but were a bit exotic and expensive. Good to see low cost units on the market now – should save a lot of fishing about inside motor windings looking for the centre point!

Well done for sticking at it and fixing the problem.

Dave

[not done it yetParticipant @notdoneityet]

Are you sure you are not running your motor in star configuration at 230 volts? Speed is proportional to Hertz. Power is a different matter and depends on volts.

[Daniel GrantParticipant @danielgrant15006]

I could well be running star at 230v, not sure how I would be able to test the output voltage from the VFD.

All I know for sure is that it didn’t run in Delta configuration so I tested the VFD on the smaller pillar drill motor (also dual voltage, and configured in Delta) it ran the pillar drill fine. I then changed the configuration on the large motor to Star and it works.

I’m going to try to modify the pulley tomorrow and test under load tomorrow evening, if it is underpowered I’m assuming it will trip the VFD by drawing too much current? I still don’t fully comprehend what’s going on inside the motor.

[Pete RimmerParticipant @peterimmer30576]

Check your parameters P00 (max voltage) that should tell you at least if it's set too low.

Also try using the keys when the motor is running, many VFD's cycle through a bunch of read-only parameters to display stuff like frequency, current, bus voltage etc as the motor is running.

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