VFD Troubleshooting - Undervoltage

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Jrmysell

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So I got my grinder set up today. I have a 1725 RPM 3 ph 2 hp 60 Hz motor and a KBAC 27-D VFD with for/stop/rev and start/stop switches with 220V. We ran a 10/3 SOOW wire from the 220 outlet from the back of our back building to where I can run the grinder. It was a 30 ft long extension that my dad wired. We tested the outlet and it works.
We wired the motor to the VFD using the low voltage specs (T1 & T7, T2 & T8, T3 & T9, and T4, T5, T6 together). The ony thing I changed from factory settings on the KBAC was changing the jumper from 110 to 220V and changing the max speed to 2x from 1x. It was already set on 60 Hz. The 220 V outlet we have is a 10-30 outlet. The wire from the VFD to the outlet is also 10/3 SOOW wire.
When I plugged it in, the power light came on to green and the status light flashed quickly between red and yellow. According to the manual it is "undervoltage". I haven't messed with it since, just unplugged it as I went to supper with my wife.
Here is a picture (not very good) of the panel on the motor. Any help would be greatly appreciated.
e5NaKly.jpg
 
How did you "test" the outlet? What voltage reading are you getting on your meter?
 
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Assuming you're getting ~220VAC, I'd double check all of your connections and make sure they're tight.
If it still doesn't work, unplug the motor from the VFD and see if it will power on.
 
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We used a DVM. We got around 110v on both legs to neutral. I don't think we did hot to hot. He googled how to check and the site we looked at said to just do that, not hot to hot. Not sure if we should have?
 
Jrmysell said:
We wired the motor to the VFD using the low voltage specs (T1 & T7, T2 & T8, T3 & T9, and T4, T5, T6 together). The ony thing I changed from factory settings on the KBAC was changing the jumper from 110 to 220V and changing the max speed to 2x from 1x.
Click to expand...

Why did you use low volts settings (110) when you are running at high volts (220)?
Is the VFD rated at 220v?
 
The motor is 220v/460v. The low setting is 220, the high is 460v. At least, that's how I understood it.
 
Ok, I see on the motor tag...
206? 220, 460

I can only assume that the 220/460 are high volts, and 206? low. You are assuming the opposite so one of us is right.
I'd jump it to high volts and double check.

That's the problem w/ China motors or electrical parts... The only way to get them right is experience or finding someone that has dealt with the same issue you are facing.

I use several PID's that are dirt cheap but the actual wiring is VERY different than the label or the instruction sheet.

I read the motor wrong 206-230/460.
I see your point.

Forget most of my post...
This will help
https://electronics.stackexchange.com/questions/183484/how-to-wire-three-phases-for-220v
 
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You tested the outlet. Now test voltage at the vfd terminals. I think you're dropping a leg in your extension cord.
 
Agreed.
This isn't a motor problem, it is a voltage supply problem.

The first thing you need to do is check the power to the unit. A 30 foot extension, plus whatever distance the power comes from the main breaker box to the "back of our building" may have too much voltage drop. If there is 110VAC on each leg, and all wires and grounds are good, then check the VFD. Copper wire is rated for up to 25 feet to keep drop below 3%. It should be 8 gauge up to 50 feet. That is normally not an issue big enough issue to cause your problem unless there is already a long run to where you are connecting at the building. Just to be sure, check the power at the building and then at the plug on the end of the extension. Both should be the same and around 110VAC.

Next - Disconnect the L1-L2-L3 at the VFD. Turn on the VFD and see if it still indicates LOW VOLTAGE. If it does, you have to check all the things that get power to the VFD.
First, check the power at each input terminal (220VAC) on the VFD. That should read 110 to ground or 220 across both legs.
Then check the power after the two fuses. If there is 110V on each leg, any incoming power problem is eliminated. If the post fuse readings are bad, check the fuses.

If all the incoming power checks are good, and you still have a low voltage indication, the VFD probably has a problem or isn't programmed right. Go to the manual and check all the programming that refers to power.

I am not sure if your VFD shuts off output when it gets a low voltage issue, but check each leg to ground on the VFD L1-L2-L3 output. If there is a voltage, they should be equal. They should read around 208 volts across any two terminals.

After reading the manual and checking the power and programming with no solution, a call to tech support will probably solve the issue. The KB guys are really good.
 
Thanks everybody. We double checked the extension outlet and it was giving off 120 from each leg. We tested continuity from the bff to the plug and realized we had the ground wired as a hot leg. We switched them in the plug and it fixed it. I started it up and it runs in reverse. We switched the 2 hot legs in the plug, still reverse, then tried switching the L2-L3 terminals in the vfd and it still runs in reverse. I planned on adding a disc grinder in the future so I ordered the vfd with a for/rev switch so I just have to leave it in reverse. But it works now. I tested it and it is night and day difference from the 1x30 I had been using. Thanks again.
 
Switching the two single phase legs will not change anything.

To reverse a 3Ph motor, just switch any two legs at the motor or the VFD ( don't worry about the 1-2-3 notation).
 
According to the manual, Jumper J1 needs to be set to the proper voltage (page 23) and if you are using two phase input, you need to connect to L1, and L2 for the input. Sooooo, you might want to check these before you do anything else.

When I kill the power on my VFD, I get a low voltage warning while it is drainjng the capacitors in it's power supply. This indicates you have low input voltage.
jim A
 
"....if you are using two phase input...."

Just a slight correction, but 220 is single phase, not two phase. It has two hot legs. (in the USA)

The transformer at the street for home power is 220 volt. It is center tapped to ground reference and any leg compared to the center tap or ground will read 110.
 
220vac has two single phase 110vac ckts referenced to neutral/ground. Each phase is 180° out of phase with each other. Call it what you want
Jim A
 
The link I provided above explains it (voltages)
Sounds like the OP has this under control.

You guys are great for replying, no doubt. Better than me.
I'm scared of electrics even tho I have a Bachelors in electronics. I do what the OP did.
Read, and learn.
 
Lol lots of speculation in this thread and misunderstanding.

Low voltage to the VFD is 110v 1ph input, high is 220v 1ph input.

Low voltage to the motor is 220v 3ph input, high is 440v 3ph input

That VFD only takes 1ph input (110-220v 1ph) and outputs 220v 3ph.

The only thing that has to be changed in the VFD is the input voltage selection jumper, J1, which only varies from 110v to 220v input. Here in the US what we refer to as 220V 1ph is technically split-phase 180deg off-set, as someone described above, where historically 2ph systems had a quarter cycle off-set of 90deg. I know in some places they refer to the half cycle off-set as 2ph also, but this is irrelevant to this thread, we can argue nomenclature over at an electrical forum. Regardless, there is no differentiation in these vfds between 1ph and 2ph power, simply put the jumper in on one post for 110v, and another for 220v

You guys would be surprised how many knifemaker's VFDs I've had to "fix" because the owner wanted to "make sure it was done right", hired an overpriced electrician, who wired the motor for "high voltage" because they couldn't figure out the above. Unfortunately, the grinder will run like that, but has no power, and can typically be stopped with one hand and little pressure grinding. In each case it's been a beginning maker, already struggling to figure out how to grind, this makes it significantly worse, and it usually takes them a year or two before they're finally are able to admit there must be something wrong. Not knowing, and having hired an electrician who must know what he's doing, makes them assume it's just how it's supposed to be.


Sounds like the OP figured it out, and it was not related to the VFD, he had it configured correctly. My concern is that someone else is going to find this thread with a similar problem, and spend a week chasing down all the wrong answers.

Finally, yes, simply switch one of the wires coming from the motor, labeled as U, V, W, in the vfd, with another to reverse the direction, changing the line inputs with 1ph power won't do anything.

Although if you had a 3ph input 3ph output VFD, this would be different.
 
Javan Christian Rhyne Dempsey
I'm currently making a 2 x 72 belt grinder and I'm having trouble wiring up my variable frequency drive it's a kbac- 48VFD hoping maybe you could help I know this is an old post but please help if you are able to see this
 
javand said:
Lol lots of speculation in this thread and misunderstanding.

Low voltage to the VFD is 110v 1ph input, high is 220v 1ph input.

Low voltage to the motor is 220v 3ph input, high is 440v 3ph input

That VFD only takes 1ph input (110-220v 1ph) and outputs 220v 3ph.

The only thing that has to be changed in the VFD is the input voltage selection jumper, J1, which only varies from 110v to 220v input. Here in the US what we refer to as 220V 1ph is technically split-phase 180deg off-set, as someone described above, where historically 2ph systems had a quarter cycle off-set of 90deg. I know in some places they refer to the half cycle off-set as 2ph also, but this is irrelevant to this thread, we can argue nomenclature over at an electrical forum. Regardless, there is no differentiation in these vfds between 1ph and 2ph power, simply put the jumper in on one post for 110v, and another for 220v

You guys would be surprised how many knifemaker's VFDs I've had to "fix" because the owner wanted to "make sure it was done right", hired an overpriced electrician, who wired the motor for "high voltage" because they couldn't figure out the above. Unfortunately, the grinder will run like that, but has no power, and can typically be stopped with one hand and little pressure grinding. In each case it's been a beginning maker, already struggling to figure out how to grind, this makes it significantly worse, and it usually takes them a year or two before they're finally are able to admit there must be something wrong. Not knowing, and having hired an electrician who must know what he's doing, makes them assume it's just how it's supposed to be.


Sounds like the OP figured it out, and it was not related to the VFD, he had it configured correctly. My concern is that someone else is going to find this thread with a similar problem, and spend a week chasing down all the wrong answers.

Finally, yes, simply switch one of the wires coming from the motor, labeled as U, V, W, in the vfd, with another to reverse the direction, changing the line inputs with 1ph power won't do anything.

Although if you had a 3ph input 3ph output VFD, this would be different.
Click to expand...

Javan Christian Rhyne Dempsey
I'm currently making a 2 x 72 belt grinder and I'm having trouble wiring up my variable frequency drive it's a kbac- 48VFD hoping maybe you could help I know this is an old post but please help if you are able to see this
 
You would be better starting a new thread, and if this thread had some info that was relevant, put a link to it i n the new thread.

Also, you need to give us all the pertinent info - input Voltage to the VFD, motor size/voltage/HP,etc.

The KBAC-48 series is a 380-480VAC 3phase input type VFD. Few people have that available unless they are in an industrial building. IIRC, they are for running big motors.
 
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