Did I screw myself by buying too big of a VFD?

I bought a Teco N3-203-CS-U. I purchased it purposefully oversized because I wanted to have some future flexibility to use it on other larger machines and it was not a ton more to go with the larger unit. I wired everything up and fired it up and it worked at the default settings.

This morning I went in and was configuring the drive's advanced settings and was trying to input the motor's parameters into the unit and ran across something strange.

I went into the advanced section of the unit and began configuring the motor:

A001 - Motor Rated Voltage - I left this as default was 230
A002 - Motor Rated Amps - I changed the config on this to be 2.2 versus the default of 8.7 and received an error. The unit would not let me save the configuration to anything under 4.5
A003 - Motor Rated HP - I set this to .5 since this is only a half horse motor but default is 3.
A004 - Motor rated hertz left at default of 60.

When I have the unit configured to .5 HP and try to run it I get an error of OVSP, Over Speed During Operation. It notes in the error section of the manual that this could be:

1. Motor load excessive or invertor capacity to small - this feels unlikely do the unit be rated much larger than the motor
2. Motor parameter error (vector mode) - a000 is set to the default of 002 so I don't think that is vector mode
3. The gain is excessive in vector mode - A000 set to 002
4. Current detection circuit fault

So I am wondering if this perhaps can't be configured to run as small of a motor as I am trying to run? Or is there simply another series of parameters with it that I am not understanding and that I need to configure to make it run with this motor.

As noted, everything works fine is I leave the motor configured as 8.7amp and 3HP but I don't want to leave it assuming there is a much larger motor running than there is.

Thoughts?

datmony said:

As noted, everything works fine is I leave the motor configured as 8.7amp and 3HP but I don't want to leave it assuming there is a much larger motor running than there is.

Thoughts?

Click to expand...

Are you worried about burning out the motor? if so there is no way around it because 4.5 amps, the minimum the drive can be set to will still burn out a 2.2 amp motor. An alternative method to prevent burn out would be installing a thermister, or thermal circuit breaker in the motor and wire it up to the vfd to turn the vfd off.

Can you rewire the motor for delta? set the motor amps to 4.5 and the volts to 132 volts. (full load amps will now be 3.8, this is less than 4.5, but I suppose 4.5 amps will no longer burn out the motor)

Vector mode by default would not surprise me.

Many larger VFD's do not allow motors about 50% smaller than their rating to be used, due to the fact that the motor FLA setting cannot be set LOW enough.

VFD needs to provide proper overcurrent protection to motor it is connected to.... Hard to control a dental drill, with a 600hp Cummins motor.. Just not that fine of control down low... Internal current sensors at bottom of their range..

Since you have over bought/sized on your VFD.. The only solution.. is to buy a big enough machine to use it on.

Asking here BEFORE purchase, can save time and bother...

I think you hit on the problem of purchasing a drive too large for the load...you can't dial down the overload protection for the small motor. There is another way to skin this cat though. Find a overload block, wire it in series with the drive motor leads and run the logic circuit through the NC O/L contacts. If the block is fitted with the proper over load heaters for your little motor, on over-current, the NC switch opens and kills the drive...just like you pushed the OFF button. You're not interrupting the output of the drive, you are giving it a simple STOP command.

Small drives and pretty reasonable..you could just buy a properly sized one and skip all the monkey motion.

Stuart

I'm working on setting up a VFD today as well. The first step I would take is to consult the parameter description in the drive literature.
MOST documentation includes the range of permissible values for each parameter.

IF values less than XX are not included in the description/instructions. then you know and can take other steps.
There is nothing wrong with fusing the output from the VFD. A broken leg will fault the drive . In fact, such fusing is shown in the set up instructions. However. The drive will not properly recognize the motor if the data is not correct. I would doubt that any "auto-tune" process would be successful.

For my own efforts today, there is a 1/3 hp motor attached to a 5 hp VFD, with motor settings set per the name plate without issue.

ETA

See page 53 of the manual
https://www.tecowestinghouse.com/Manuals/TECO N3 Instruction Manual.pdf

seems that motor data is only relevant if Vector Control is selected. Worth a check.

You have several possible work arounds.

No matter what you will need to set the max current to the minimum. This means you will then need to set the hp parameter to 1.4 hp. This will give you a reasonable level of short circuit protection but not protect the motor from over load.

You can still get overload protection by adding an overload relay into the motor circuit and using the overload signal to inhibit the VFD. This would be a rather complicated and costly addition but would give the same protection as a properly sized VFD.

The other method is to add fuses to the incoming power to the vfd sized for your motor load. For the .5hp motor running on 230V, you would need use 4A fuses with single phase input power. This is not ideal but would work.

Gleaned from reading the manual

Chapter 4 Software Index
4-7
4.2 Control Mode Selection
The N3 Series inverter has three control modes:
1. General Vector Control Mode
2. VT Vector Control Mode (Special for Fans, Blowers, Pumps).
3. V/F Control Mode
。
The user can choose these modes with the digital ke
ypad according to the application characteristics.
The factory setting is general vector control mode.
Before operation, please set the control mode and
the relative parameters of the motor in accordance
with the following flow chart. (The Vector control
mode only applies when the inverter is power matched to the motor, or varies by 1HP rating).
※
Note:
1. Use V/F Control Mode:
(1) Use one inverter to drive several motors simultaneously
(2) Motor’s nameplate is unknown
or motor’s specifications are too special, it will

cause Auto-tuning fault.

(3) Specification of inverter and motor differ more than 1 class

You could always buy a bigger motor most lathes could benefit with a bigger motor than .5 HP.
If you get a VFD rated motor it can be overclocked. I over clock my 1800 RPM motor to 4000 RPM not as much gear or belt changes.

I would check amps and voltage to all 3 hot leads with motor running, and probably hz while i'm there, then motor rpm. If its good, install an appropriate amp breaker between vfd and motor. Some of the systems I've been checking out can run more than 1 motor, so I would have to guess that you could run a smaller motor. Example, would be a lathe that also has a 3 phase coolant pump motor. You probably won't dial the coolant pump motor in with fancy settings, but amps and voltage should be fine.

atomarc said:

I think you hit on the problem of purchasing a drive too large for the load...you can't dial down the overload protection for the small motor. There is another way to skin this cat though. Find a overload block, wire it in series with the drive motor leads and run the logic circuit through the NC O/L contacts. If the block is fitted with the proper over load heaters for your little motor, on over-current, the NC switch opens and kills the drive...just like you pushed the OFF button. You're not interrupting the output of the drive, you are giving it a simple STOP command.

Small drives and pretty reasonable..you could just buy a properly sized one and skip all the monkey motion.

Stuart

Click to expand...

I will likely just buy another and then use this one for an eventual conversion on one of the mills. That was the main reason in buying one this size anyways was future flexibility..... I just did not anticipate not being able to run a small motor with it too. That still just seems odd to me....

Crossing fingers because as I noted, it still just seemed odd to me that I couldn't run a small motor and just have tons of overhead on this drive. A quick call to tech support was super helpful hopefully. There is another parameter that is the no load current setting under A130 supposedly that is likely set to high for the motor configurations I was trying to input. I will check that out tonight and see. Hopefully all will be right in the world with a quick software setup. I figured it would be that easy but just wasn't seasoned enough on these to know what parameter I might be missing. I will chime back in with results.

We are all assuming the motor is three phase.... Is it?

If you insist on vari-speed and all the bells and whistles, perhaps not.

But it should be willing to function as solid-state phase converter/inverter. Just need to get the settings correct.

SteveBausch said:

We are all assuming the motor is three phase.... Is it?

If you insist on vari-speed and all the bells and whistles, perhaps not.

But it should be willing to function as solid-state phase converter/inverter. Just need to get the settings correct.

Click to expand...

Definitely. 3 phase 1/2hp. That was what threw me for the weekend was that it just didn't make sense to me that I couldn't configure the parameters to accept the smaller motor. The guy at the Teco help line was very helpful and he even noted, "you know.... I had to learn about that setting the hard way too." He indicated that I shouldn't have any issues running any size three phase motor off of it and to just drop a call back if I hit any roadblocks.

Now if I can just get my 4pm meeting over with I can run home and configure this and see if she works. Should take all of about 5 minutes to do the settings I need. Fingers crossed....

So that did help. Motor is now recognized as a .6HP with 2.2amps FLA. For some reason when I drop it to .5 it errors out. I need to call support back again to see if there are any other settings I need to configure it or if that might be correct. That is also what auto tune finds too....