VFD issue

Kevin McGovern

Kevin McGovern

Joined
Jul 31, 2015
Messages
3,118
Well I had intended to put my VFD controlled disk grinder in my clean shop since the VFD is not sealed. I inadvertently left it on the bench behind me when i was grinding the other night. Now it wont run my motor. It is showing a short fault according to the status light. the power light and status lights DO work. You can also hear it click on as is normal. This is the model: KBWA 23D http://kbelectronics.com/data_sheets/kbwa.pdf

Is there any hope for this thing? It had barely any dust on the case when i realized my error. I blew it out with compressed air. I would hate for it to be scrap since it's only been used less then 3 months.
 
Not to say that isn't what happened to your motor, but I've been running an unsealed motor on my grinder for about 2 years,.. its covered in knife dust, hasn't crapped the bed yet. I know its going to happen, and I am hoping it will soon though so I can have a reason upgrade. I'd just be surprised if one night of grinding killed your motor, I could be wrong though.
 
The motor is sealed. I believe the problem is with the VFD. So I am asking if the VFD is toast, not the motor.
 
What fault light is lit ?


Hook it up to another motor for testing



Take both to a motor shop for testing.
 
kdogmcg said:
Well I had intended to put my VFD controlled disk grinder in my clean shop since the VFD is not sealed. I inadvertently left it on the bench behind me when i was grinding the other night. Now it wont run my motor. It is showing a short fault according to the status light. the power light and status lights DO work. You can also hear it click on as is normal. This is the model: KBWA 23D http://kbelectronics.com/data_sheets/kbwa.pdf
Is there any hope for this thing? It had barely any dust on the case when i realized my error. I blew it out with compressed air. I would hate for it to be scrap since it's only been used less then 3 months.
Click to expand...

check all your motor and vfd connections. check your motor with multimeter, you should see low,equal ohms between phases(5 to 10 ohms and all three should be within 1 ohm) and each phase to ground should be an open or at least 10 megohms. i would disconnect the motor at the vfd and check there, if all readings are good you have eliminated the motor and cable.
scott
 
Your indicator is showing a phase to phase short in the wires to the motor, or in the motor.

Firs, find out where the short indication is coming from. Disconnect the wires to the motor from the terminals in the VFD ( unplug the VFD power first) and see if the short light stays on. If yes, the problem is the VFD, if it goes out, the problem is the motor.

Check all wires in the indicated device. Maybe something got shorted or disconnected. Check the power wires between the VFD and motor for a short in the plug or connectors.
Next, open the VFD with the power plug unplugged and blow it out well. Look for anything that seems odd.
Blow out the motor if it is not TEFC. Non-TEFC motors can fail easily on knife grinders.
Check all fuses on the VFD and the breakers at the power panel ( I know you said there is power, but re-set them anyway.
After checking everything, connect it all back together and see if it runs right.


I just noticed the drive you linked. What motor are you running with it? That won't run any size motor that will run a grinder. I use a similar VFD to run a 1/3HP motor on a small wood lathe.

If the above checks do not resolving things, call the VFD's tech support.
 
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It is running a 1/2 HP 3 phase motor (brand new, TEFC) on a Disc sander. It was running great, and it had plenty of power for what I'm doing (flattening scales and tangs, final flattening of flat grinds, bolsters). Thanks for the advice. I installed it with proper wiring connections and I used cable glands on the junction box, but I have moved it a few times and the VFD is not hard mounted yet, so it could have pulled loose. I don't see anything out of place on the motor or the VFD end, but I will disconnect the motor lead and see if that clears the fault. thanks again.
 
Have you tried unplugging it from the power source for a few minutes?
I don't mean to sound obvious, but sometimes I overlook the simple fix.
 
Haha, just checking. My VFD, although a different model, has to be unplugged sometimes when I trip it.
 
1/2HP is the max that VFD will handle. It will only run it under any load for a few minutes at a time. Over loading the VFD will usually cause an overload signal and stop the motor, but it may cause a component failure. If the overload trip is the problem, letting things cool down and resetting the drive ( power off then on) should solve it. If a component in the power supply is failed, the VFD is a goner. Probably not the issue here, but a problem down the road.
 
Thanks for the heads up. I have never run it under load at even 75% speed. I have never bogged it down. It has an overload fault code function, but the code I'm getting is for a short. I maybe used it 4-5 times for maybe 5 minutes at a time. I hadn't used it in a while and now this. That's what is making me think it is not operation related, but dust or more likely i pulled something loose. I will report back with my findings. Thanks again.
 
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