Variable speed spindle motor, 220V blowing fuse - Page 1
Forum section: electronics / beginners

author: KTCNC
author_rank: Newbie
timestamp: November 13, 2021, 05:45:14 am
content: Hello,Ive got a VFD + motor that suddenly started blowing the fuse its connected to the second I turn the power on, before I can start the spindle itself making me think there is a short somewhere.The fuse only blows when motor is connected to the VFD. It worked perfectly 2 weeks ago.The motor: 220V, 2.2KW, 0-400hz (0-24000rpm), 3P+groundThe VFD input: 220V, 50hz, 1P+groundThe Fuse: 220V, 50hz, 16A, 1P+groundThanks in advance

author: elekorsi
author_rank: Regular Contributor
timestamp: November 13, 2021, 07:15:15 am
content: Did you measure motor windings? Resistance between the windings and insulation resistance against the chassis? Even though it is very unusual that the fuse for the VFD power supply would blow in case of motor failure.... Usually the VFD goes into an error if the motor is faulty...What brand/model of VFD you are using?Also a quick check for the VFD power stage is to measure the diodes in the IGBTs. You can do this without opening the VFD, between the DC bus and motor outputs U,V,WSometimes the quickest way of diagnosing the VFD is to connect another good motor, with new cables of course. If it still trips, the VFD is toasted...Simple test that you can built for the VFD is with 3 incandescent light bulbs (old 230V ones) connected into delta. You then set the U/F parameters very low, something like 230V at 2Hz. Run the VFD and you can clearly see if it turns on the windings correctly. If anyome interrested i can show it...

author: KTCNC
author_rank: Newbie
timestamp: November 13, 2021, 08:09:57 am
content: Thank you for the quick response.There is continuity between the 3 phases, they all measure 1-1.2ohm. and between the chassis ans each of the phases it measures 1Mohm.The model number of the VFD is HY02D223B.unfortunatly I do not have another motor to test with

author: Kleinstein
author_rank: Super Contributor
timestamp: November 13, 2021, 08:33:46 am
content: 1 Mohms to the chassis is not a good sign. This would normally not trip the fuse, but it may trip the GFI/RCD (1 M of normal resistance would not, but the isolation failure can be nonlinear).So the question is what type of fuse blows. VFD and GFI is anyway a tricky combination.Not all motors like being driven from a cheap VFD, as there are extra voltage spikes that may damage the isolation.

author: KTCNC
author_rank: Newbie
timestamp: November 13, 2021, 08:38:34 am
content: I have a feeling I might have misunderstood the insulation testing part. I tested it using a normal Multimeter, I do not have a insulation tester / magger

author: Siwastaja
author_rank: Super Contributor
timestamp: November 13, 2021, 09:44:21 am
content: Fuse is of wrong size/rating, or VFD is broken.Check the fuse value from the VFD manual. If this is the right size, get a new VFD. If the current VFD is new, return it for repair or ask for money back.

author: elekorsi
author_rank: Regular Contributor
timestamp: November 13, 2021, 12:08:02 pm
content: Yes the insulation resistance should be measured with the insulation tester...I said earlier that it is unusual that if the motor would be bad, that the fuse would blow. But now that i see what VFD you have, i wouldn't be surprised if it's protection functions are that bad, that it would rather blow the fuse than activate the short circuit protectionNo offense, but those chinese VFDs are quite crappy...Best option would be to get a 3ph motor somewhere for the test, maybe a neighbor or friend has one. Any small 3ph motor with the 230/400V rating will do it, just set the U/F first, accordingly to the new motor. Probably 230V/50Hz. And you will need to wire it in delta if it was previously connected directly to 400V mains.But i wouldn't be surprised that both are toasted, the motor and the VFD. If the motor has a short to the ground and VFD's protection functions are not working properly, there is a high possibility that IGBTs are also gone. Did you try checking the IGBTs, as i mentioned before? DC bus to output? Should see the diodes of the IGBTs...

author: KTCNC
author_rank: Newbie
timestamp: November 13, 2021, 02:09:32 pm
content: I think I might have solved it. There was no problem with the VFD or the motor at all it seems. It looks like it was a bad connection in the cable, disconnecting the motor from ground and it all worked. The weird thing is that I have not done anything to the connector. And measuring between ground and all of the phases did not show anything out of the ordinaryIf in the future I want to upgrade my motor/VDF, do you have any suggestion on what I should look for?Thanks again for all the quick responses and suggestions

author: Siwastaja
author_rank: Super Contributor
timestamp: November 13, 2021, 06:45:38 pm
content: What do you mean by "disconnecting motor from ground"? What exactly was connected, how and where?Also what do you mean by "ground"?You may have a serious safety issue, that's why I'm asking.