Thread: VFD for 3 Phase Mini 30

HELP!

OK we just got everything wired up. I ran the initial test at 5Hz as per the instructions and that worked fine. Next I stopped the machine (with run/stop button on VFD), changed the frequency to 50Hz and tried again. The machine ramped up but then gave an error OCC (Over current at steady speed). Stopped and powered off the VFD to reset the error. Now I get OCA (Over current at acceleration) whatever frequency I try to run at.

I am hoping this is not too serious, does anyone know what is up?

Cheers
Graham

UPDATE

I checked my parameters. V/F Pattern was on 60Hz so I changed it to 50Hz. (Could that have caused a problem when I ran it at 50Hz before?). My machine has 2 motors so I tried the other one (spindle moulder) that is working fine. If I isolate back to the planer/thicknesser/saw motor I still get the OCA error. Found an internet post with same error and someone suggested the possibility of a grounded phase. I presume checking connectivity between each phase and earth will isolate that problem. Will check it out. In any case it appears the VFD is OK which is good news.
Graham

Hi Graham,
I assume the planer/thicknesser/saw motor has a lot more spinning mass than the spindle moulder?
Whats F_01=?
Thats your acceleration ramp time. Try making it larger until the OCA error goes away.

Stuart

F_01 was on 5 by default. I tried 10 with no success. Dave suggested I take the belt off the motor and see if it starts with no load. Could be a bearing or just too much load. I will let you know how we go. Just a bit wierd that it started the first time, but not after that?

Cheers
Graham

Sounds like a good plan.

Whats F_05=?

Stuart

Good plan, but no joy. Removed the belt and motor spins freely by hand, but still get OCA error. F_05 was default on 4. I changed it to 1 but that was after the error had happened. I thought it should be on 1 since we are at 50Hz here, but Dave said it should be on 60Hz (F_05=4).

It seems that something has happened to the motor, since the other one works fine. It errored on OCC the first time I tried to run it at 50Hz. Is there anything I can do to test the motor?
Graham

Did it error at about the same Hz?
How long into the 10 second ramp?
I think you'll need someone with a megger tester to have a look at it.

Stuart

Hi Stu

The error comes up immediately I press Run. I just tested with my little Dick Smith multimeter. Removed all the Delta connectors and wires so I could test each coil separately. All 3 coils measure 10 ohms, No leakage between any coil to earth. Testing coil 1 to 2 shows no connectivity. Testing coil 2 to 3 shows no connectivity.Testing coil 1 to 3 does a funny thing. When I first touch the contacts, the meter flashes to around 150 ohms, then shows 1 (no connectivity). Maybe this is showing a potential problem.

Dave said I might need a megger. I don't know what that is?

Interestingly the motor that is working has been rewound while the previous owner had it. Te one with the problem is original I think.

Cheers
Graham

We are heading out of my depth.
Your multimeter tests resistance at 9V
As I understand it a megger tester does the same but in this case something around 500V(maybe a more)

Someone that knows more might be able to explain the 150ohms thing.

Might be time to take it to a motor rewinder, they will have the gear to test it.

Stuart

Yes I did some googling and it appears you need to test at higher voltages to diagnose properly. This really sucks. If only it was the other motor I could still use the machine! I guess electricians are the only people with meggers? Pity I didn't get him to test when he was here, but I thought it was probably a VFD problem since I hadn't tried the other motor at that stage. This might get expensive. I guess the motor might have been ready to go, but presumably the VFD tipped it over the edge. I think its probably cheaper to buy a new motor than rewind. I live in a remote location so that is a problem for me. I really just need to know if the motor is cactus or not.

Thanks again for your help
Graham

I'm not sure if many electricians would have a megger tester??
Only thing I can suggest now is testing coils 1 to 3 in all four possible ways. Though I dont know if it will tell me anything it might help someone else. You might find its shorted in one of the four ways? Who knows maybe if you are luckly its a wiring problem before the windings.

Isnt this the motor with the strange shaft?

Stuart

Something just dawned on me. If it is happening as soon as you hit the run button you might be in luck.

As I understand it. As the output V is related to Hz, if the VSD is erroring as soon as the run button is pressed. To me this would mean the V was something less than 10%. Now to have over current at that V and Hz would be something above 60% of the VSD's rated current. I would have thought the fault would need to be close to the end of a winding or before the windings. Now if its "close to the end" that does you no good at all. Before would be a good thing.
And of course I may have the above completely wrong. With luck someone that knows what they are talking about will show up.

Fingers crossed.

Stuart

p.s. whats F_18=?

Interesting that you say that. I was on the phone to WA Rewinds and he reckoned the weird thing happening on my ohm meter might indicate a faulty connection. I removed the junction box on the motor and got behind it to have a look. Most of the wires going to the junction box from inside the motor have cracked insulation so that I can see bare wire in places! The problem may be well before the windings if that is the issue. There doesn't appear to be much spare cable to re-terminate and I am not sure how the wires are actually terminated to the brass screw connectors. Looking on line and I am waiting to talk to the rewind guy again. I guess the whole motor may need to come to bits to install new main wiring?
Graham

OH OH!!!!

Pulled the terminal box on the faulty motor and attempted to insulate the wires for the couple of inches I could see. Wired it all up and gave it a go.

A BIG BANG from the VFD and tripped out the whole shed! Must have been a short further down the line I am guessing. The VFD now comes up with a LV error (looks like LU but presume it is LV). Manual says "Voltage too low while not operating". Detection circuit defective. Return the inverter for repair.

I think I was trying to be too clever for my own good. I guess now I will have to send it back to Dave. Do you think he will repair it under warranty?

What a saga

Graham