VFD Buss Overvoltage on ramp up
VFD Buss Overvoltage on ramp up
(OP)
We have a machine in the field with a Yaskawa V1000 15HP VFD installed in it. It is running a conveyor. We are controlling the speed via a 4-20mA signal to the drive which varies from 0-60Hz. We used the canned "Conveyor" setup from the menu.
Here's the problem. When the customer runs the conveyor at 50% speed (30Hz) or below, it seems fine. When they attempt to go over 50%, they get a DC Buss Overvoltage fault. We are not decelerating during the fault, so we don't think it's a regenerative problem. We had them run at 50% and then change it to 60% speed and it trips every time. The supply is constant 482V. We had a line reactor feeding the drive and it appears to have opened a leg. So, we've bypassed it for the time.
Everything I've read says regenerative problems cause overvoltage errors. But, the problem ONLY happens on the ramp up when we get past the 50% speed mark. I'm kind of stumped here. I even had them monitor the Buss voltage through the drive and it never went past the 700V range. So, something is happening faster than the drive would display. Any thoughts?
Here's the problem. When the customer runs the conveyor at 50% speed (30Hz) or below, it seems fine. When they attempt to go over 50%, they get a DC Buss Overvoltage fault. We are not decelerating during the fault, so we don't think it's a regenerative problem. We had them run at 50% and then change it to 60% speed and it trips every time. The supply is constant 482V. We had a line reactor feeding the drive and it appears to have opened a leg. So, we've bypassed it for the time.
Everything I've read says regenerative problems cause overvoltage errors. But, the problem ONLY happens on the ramp up when we get past the 50% speed mark. I'm kind of stumped here. I even had them monitor the Buss voltage through the drive and it never went past the 700V range. So, something is happening faster than the drive would display. Any thoughts?





RE: VFD Buss Overvoltage on ramp up
Try contacting Yaskawa, especially if it's still under warranty.
RE: VFD Buss Overvoltage on ramp up
RE: VFD Buss Overvoltage on ramp up
This could be a problem where there is instability in the speed control system which is causing the vfd speed to vary up and down.
This can be due to a problem in the VFD, or a mechanical resonance.
Is the VFD operating with an encoder feedback system?
Best regards,
Mark.
Mark Empson
L M Photonics Ltd
RE: VFD Buss Overvoltage on ramp up
RE: VFD Buss Overvoltage on ramp up
I have to agree with Mobius. It sounds like the VFD might have gone bad.
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RE: VFD Buss Overvoltage on ramp up
RE: VFD Buss Overvoltage on ramp up
They were installed on a stiff 600V system with no line reactors and I suspect they were damaged by surges. Replacing them fixed the problem.
RE: VFD Buss Overvoltage on ramp up
I have seen drives with a failed diode suffer from over-voltage problems. Basically, the diode switching, reactor and capacitor caused a ringing and the peak of the ringing washigh enough to trigger the over voltage trip.
If it never worked, then I'd also suspect something as simple as the belt jumping causing a momentary regeneration.
RE: VFD Buss Overvoltage on ramp up
We are going to replace the drive and see if the problem goes away. This is a new installation and I'm not sure if the conveyor had trouble from the start or not. The conveyor is brand new as well. I am working with our local dealer on site. We will be sending our own service guy next week.
RE: VFD Buss Overvoltage on ramp up
RE: VFD Buss Overvoltage on ramp up
I'll keep you updated.
RE: VFD Buss Overvoltage on ramp up
Best regards,
Mark.
Mark Empson
L M Photonics Ltd
RE: VFD Buss Overvoltage on ramp up
But we do love the fringes around here...
The belt (assuming rubber based) is stretching under the force applied by the motor against the load carried by it and acting like a "rubber band" where it's snapping back and getting pulled forward in an oscillating manner. If the snap backs get too excessive, the drive regenerates. It only gets excessive when the speed gets above 50%. Simple test, see if it happens with no load on it. If not, keep increasing load until it does.
There is a company called Conveyor Dynamics that makes a living out of the prevalence of this issue in conveyor systems. The founder is a Ph.D in wave dynamics.
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RE: VFD Buss Overvoltage on ramp up
RE: VFD Buss Overvoltage on ramp up
That's a very good theory. However, it's an incline belt, so the coasting theory seemed unlikely to us. But, it does seem probable. Unfortunately, I've not been to see the installation. But, from my experience, when you get to conveyors of this size in the recycling industry, they end up being chain driven and often metal instead of rubber. But, I can not confirm that as of yet. I've also discovered that the conveyor is brand new and manufactured by one of our other dealers. Thanks for the ideas! We'll change the drive out Wednesday or so and see if the problem goes away. I and the drive manufacturer do not think it will.