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Troubleshooting a VFD (variable frequency drive)

F

Finn Posner

Joined
Nov 1, 2008
Messages
54
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6
Location
Turnwater, Washington
Hello to all fellow woodturners. I'm hoping either you, or you know someone who can help/direct me how to solve my VFD problem.

I have a used Delta 46-745 with the 110v, 1.5hp motor. I bought it used as a backup/fixer upper. And of course as a used lathe the major problem is in the electrical side of the house. By the way I'm a civil engineer who tries to stay as far away from electricity but gets drawn back in nonetheless.

When you start the lathe the speed seems to build slowly and when you engage a tool for example in bowl turning, the speed slows and shortly the lathe quits and the power and fault lights blink. You can restart it after a few minutes of rest. I took the motor to a "motor" shop and they applied 220v, which is what the motor requires, and it seemed to turn freely. So my deduction is that the problem is in the VFD.

Any ideas how to troubleshoot Doug's VFD nameplate (resized).jpg Doug's motor nameplate (resized).jpg Doug's VFD (resized).jpg this? Should I just replace the VFD and if so what's your recommendation on brand and model, of course based on our common interest of doing it as "inexpensively" as possible.

Thanks so much - Finn Posner
 
First if you have a multi meter & can find a tech rep from delta you can likely isolate the problem.

I had an issue with a general 260. The nice guy at General walked me through settings on the controller and what we could see in the read out of the controller. It was something he could not correct so he put me in touch with the controller supplier. Their guy walked me through a couple of multimeter readings. Verdict it was fried. New controller fixed it fine.

If you are stuck with replacing things until it is fixed
You might replace the potentiometer first it is what the speed change knob attaches to.
You should be able to read some numbers on it.
Potentiometers cost from $7-$20 The controller is more like $250
Changing it requires a soldering iron and solder.
Take a photo of the threesomyou get them in the correct order on the new one.

Better to spend $20 then $250 than to spend $250 and then findoutnyouncould have fixed it for $10.

If you need a controller radwell international was a good source for me.
 
There is an older thread that discusses the same problem that you are having, but I don't know if it will be of much help: Delta 46-745 VFD Problem

I noticed that I was able to find the Baldor manual, but unfortunately I didn't post a link. Maybe there is hope that the manual is still available on the Baldor site.

Your description of the problem sounds very much like a programmed shut-down due to an over current condition or possibly a ground fault. You could try plugging it into an outlet that is on a different breaker although I don't really think that will show anything. If you have a multimeter you could check to see if there is any measurable resistance between the frame and either power lead. Since our previous discussion I have been wondering if the previous owner might have installed a new VFD, but possibly didn't program it correctly.

I think that the best course of action would be to see if the VFD manual is still available on the Baldor site so that you would be able to interpret any fault code.
 
Larry Komroff said:
Here is link to the manual. http://www.baldor.com/Shared/manuals/715p-802.pdf In looking through the manual and by your description, it appears you have Fault code 1. With the power disconnected, you might want to check all the connections and make sure a screw did not come loose. Pay careful attention to the motor connections.

Larry
Click to expand...

Larry, you are a life saver. :)

The fact that it runs until you apply a torque load seems to indicate that the inverter is working, but something is causing it to detect a fault and shut down. I would take Larry's advice on what to check.

As a "last ditch" effort if everything else checks out OK, don't rule out a problem with the motor. While I don't know what testing the motor shop did when you took the motor in to have it checked, it could be that they only hooked it up to to three phase 60 Hz power and made current measurements. That would normally be sufficient, but it wouldn't tell the whole story for a motor that has been used with an inverter. A typical failure mode for motors that wasn't designed for, but nevertheless was used in inverter duty is corona induced insulation breakdown in the field windings caused by high voltage spikes. Under normal sine wave power this breakdown might not be observed. The insulating rating on that motor is class B which is typical for general purpose motors of that age. Newer motors designed for inverter duty typically are wound with wire that has a much higher breakdown voltage rating, usually class F.
 
Just to confirm:
The motor is as single volt, 3 phase 220. Tested and works

The VFD is
- 110v in, single phase, albeit 17 amps, which is a fair bit. Check the breaker on your circuit.
- 220v out, 3 phase.

Grab a multimeter, stick it on T1, T2. You should see 220v
Now try, T2 , T3
Then T3, T1

All should be close to 220v

Changing the speed should have no effect on voltage.

Check the mechanicals on your lathe, that it all sp8ns freely. Added. Drop might be an issue causing overload.

Other than that, I agree with Bill. It sounds like overload and shutdown.
 
Very good point, Brent.

Olaf, the inverter output is pulse width modulated to effectively provide the equivalent of sine wave AC power AS FAR AS THE MOTOR IS CONCERNED, but not as far as a multimeter is concerned unless you have a multimeter specifically designed to be used for this purpose. Also, the inductance of the motor windings creates high voltage spikes that can be over a kilovolt. Even if these voltage spikes don't damage the multimeter they certainly will confuse the reading.

Actually, changing speed changes both frequency and voltage. The reason that voltage is reduced as the speed is reduced is to prevent magnetic saturation of the iron.
 
First of all please let me thank everyone who took the time to read and respond to my plea for help. And while they are not part of this forum, I also want to thank some of my electrical engineering coworkers who helped this civil engineer avoid getting fried.

So the short story is the lathe now works in all directions and speeds.
The longer story is that it took numerous phone calls and emails but I eventually bought a new KBDF-27D, 1.5;2HP, 1-Phase, 115/230V (Input), IP 20 Enclosure, Variable Frequency Drives from State Motor and Control. With shipping the drive cost just under $250. They were very patient as I asked a lot of questions. I guessed at the wiring because the old and new drive were not labeled the same, but the new drive ran albeit at only one speed. After consultation with my electrical coworker he showed me how to program the stuff I needed and now it works great. I even changed the display from Hz to the RPMs. I'm even thinking about buying a recent Craig's List ad about a Jet 1642 that also needs a new VFD!!
 
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