# Yaskawa J7 Vfd Giving Oc Fault Without Motor Connnected



## Techie1961 (Feb 4, 2016)

I'm trying to connect a VFD that I had kicking around to control a belt sander that I'm rebuilding. I wasn't sure of the condition of the drive so connected it up and give it a spin. It powers up the display okay and I can do programming on it but when I try to put it in RUN mode, I get an OC message right away. Even without a motor attached. Some reading points me an IGBT being shot.

Anyone have any experience with these that can share their knowledge? I'm not adverse to opening this up and replacing components but don't want to mess up a drive that otherwise might be okay.


	

		
			
		

		
	
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## Chip Hacket (Feb 5, 2016)

I have used these before.  I'm afraid this doesn't look good.  With power removed make sure there are no shorts at the T lead connections.  May want to reset the parameters to factory default and try running from the keypad.  It should ramp up to frequency with no motor attached.  Verify input voltage of ~220V.  Good luck.


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## mmprestine (Feb 5, 2016)

Was the drive used prior to this?  If so, reset all the parameters back to stock and retry the tests.  There is a parameter to reset to default.


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## Techie1961 (Feb 5, 2016)

mmprestine said:


> Was the drive used prior to this?  If so, reset all the parameters back to stock and retry the tests.  There is a parameter to reset to default.



Yes it was. I was thinking though that maybe it's because it is connected only on two leads instead of three. I was of the understanding that it will run single phase but maybe there's a setting somewhere.


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## Techie1961 (Feb 6, 2016)

mmprestine said:


> Was the drive used prior to this?  If so, reset all the parameters back to stock and retry the tests.  There is a parameter to reset to default.



I can't seem to find that. There is one for clearing history though.


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## Techie1961 (Feb 6, 2016)

I tried the N01 parameter at 12 and 13 and it still gives the oc condition.


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## Chip Hacket (Feb 6, 2016)

Any luck with your VFD


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## Techie1961 (Feb 7, 2016)

Chip Hacket said:


> Any luck with your VFD



Nope! I have tried to disassemble it to look for any apparent failures and pretty much tried everything that I can think of. My experience with these is that there is usually something very visual like a capacitor laying loose inside the enclosure but not with this one.

The only thing that I can think of to try next is to hook it up to 3 phase power.


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## Steve Shannon (Feb 7, 2016)

What does the OC fault signify according to the manual?


 Steve Shannon, P.E.


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## Techie1961 (Feb 7, 2016)

Steve Shannon said:


> What does the OC fault signify according to the manual?
> 
> 
> Steve Shannon, P.E.



They all seem to be with the motor connected. I think it's likely the drive is shot but was hoping to resurrect it.


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## mksj (Feb 8, 2016)

If it was used on single phase, it may be that the capacitors went from the increased ripple. If you have a capacitor tester you could remove them and test each capacitor, more than likely more than one things fail in a cascade and probably toasted.


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## Keith Foor (Feb 16, 2016)

Gonna sound dumb maybe, but you realize this is a 3 phase input VFD right?  Did you connect it to 3 phase power or single phase?



Never mind, I didn't see where you said you were going to try connecting it to 3 phase next.


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## Techie1961 (Feb 17, 2016)

Thanks for replying. It is a 3p unit but when I contacted Yaskawa, they say that it can definitely be connected to 1p but the drive has to be derated by about 60-70%. I did try it on 3p though and it didn't work either.


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## tmarks11 (Feb 17, 2016)

What kind of motor are you connecting it to? Voltage, number of phases, hp rating, etc?  Also, recommend you take a multimeter between each phase of the motor and between each phase and the motor ground and report the resistance reading.

I am inclined to think that this could be a bad motor vs a bad VFD.



Techie1961 said:


> It powers up the display okay and I can do programming on it but when I try to put it in RUN mode, I get an OC message right away. Even without a motor attached.



Notice the "magnetic contactor open on the inverter output side" in the excerpt of the manual you posted.  What that is telling you is if you push RUN without a motor attached (which you shouldn't do), you will get the OC warning to tell you no motor is attached.


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## Techie1961 (Feb 17, 2016)

tmarks11 said:


> What kind of motor are you connecting it to? Voltage, number of phases, hp rating, etc?
> 
> 
> 
> Notice the "magnetic contactor open on the inverter output side" in the excerpt of the manual you posted.  What that is telling you is if you push RUN without a motor attached (which you shouldn't do), you will get the OC warning to tell you no motor is attached.


Interesting! I'll have to check it out again. When I talked with Yaskawa, they seemed to think that if the output was empty and there was an OC, it was definitely no good. Will let you know though. Thanks!


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## Techie1961 (Feb 18, 2016)

I tried to connect it to a known good motor. Still no good.


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