Puzzling VFD/motor interaction

As part of a modernization/rehabilitation project on a Rotex planer, I have mated a TECO JNEV-201-H1 VFD (220 volt, 1 phase input, 3 phase output, 1 HP, V/F or sensorless vector) with a Baldor M3546 motor (208 - 230 volt, 3 phase, 1 HP, 1725 RPM). Both are new and seem to function properly, indeed perfectly, with one puzzling exception -

In vector mode, on first attempted motor start after powering the VFD, frequently the motor will twitch in fractional rotations forward and backwawd while the VFD frequency display will flicker erraticaly. So far, pressing the VFD's motor On/Off button twice to remove and restore power to the motor will correct the problem and all will be well until the next time the motor is again started after the VFD has been powered down and subsequently powered back up. As far as I can tell, all parameters in the VFD are set correctly for the connected motor.

While in a purely manual mode, which this application is, this problem is no more than a minor annoyance, in a more automated situation it would be unacceptable, and I'd really like to understand whats wrong and to correct it. I would greatly appreciate any insights fellow forum members may have on this. Thanks in advance.

I have the TECO JNEV-1P5-H1 VFD and have not had any problems so far with the motor "twitching". If the Hz pot is turned all the way down it did do that but that was out of the SAFE range of the motor anyway.

The manual that comes with the unit is incomplete you will have to down load the complete one or get it off of the CD.

In vector mode there apears to be many other settings that are associated with vector mode. Does it do it when not in the vector mode?

Maybe reset the unit and start over with the setup.(F52 set to 020 will reset it)


Don

Thanks Don -
Based on limited experimentation so far, it has not done it in V/F mode. I have printed out the entire manual from tfhe CD, even had it bound at a local copy shop. Will give F52 a try and see if it improves the situation.
Steve

Could this have something to do with some sort of self-tuning action by the VFD, so it can figure out the characteristics of the motor to which it is connected?

My telemechanique will hunt a little (rocks back and fourth a couple times about 10 degrees) the first time you run it after it's been sitting turned off for a day or two. After the first spin-up it behaves perfectly no matter if you power it down or leave it idle.

Not much help, but you're not alone.

Jim Shaper said:

My telemechanique will hunt a little (rocks back and fourth a couple times about 10 degrees) the first time you run it after it's been sitting turned off for a day or two. After the first spin-up it behaves perfectly no matter if you power it down or leave it idle.

Not much help, but you're not alone.

Click to expand...

Jim Shaper,

When you say 'turned off' do you mean power to the drive has been disconnected or simply the OFF button has been pushed?

Stuart

I am wondering if Vector is of any benefit on a planer? ( I might be missing something? )

My 1.5¢
Doug S.

Just when the drive has had power disconnected for a length of time.

The way I have my vfd wired, there's a master on/off power disconnect switch and then the drive functions via logic inputs for fwd/rev via the contactors in the lathe's original control circuitry. The motor is directly wired to the vfd.

When I use the lathe, I have the DRO wired into a switched outlet that comes on with the master power switch, so I just leave it all on and turn it off at the end of the day.

rklopp -
Interesting idea - I will try to get up the courage to let it hunt long enough to see if straightens itself out, rather than continue to react with concern for imminent VFD self destruction.

Jim Shaper -
Yes, good to know that you have something similar - rocking back and forth is a good description except that the last time I observed this it actually was running very slowly backwards for the second or so it took me to respond. All testing so far has been with the motor unloaded.

Doug S -
As to the possible advantages of vector mode, I don't know either and am hoping to learn something from this project. I have 1 HP Hitachi V/F drives on both a band saw and a drill press and have been very pleased with these applications. The price was actually lower for the TECO sensorless vector VFD than for another Hitachi V/F, based on Dealers Electric and Drives Warehouse pricing, So I thought I would go for the TECO and have both V/F and vector options available.

By the way, the Rotex planer is hydraulically operated and the VFD/motor system powers the pump.

Thanks to all responders.

Steve

I had a motor do something similar when i was experimenting with the torque boost parameters on a Hitachi drive ( L22-037). I set it so I thought it would give me higher starting torque for a 17 inch lathe. I had to return it to the default parameter or the motor would just vibrate.

Not sure how the Teco unit does its motor tuning, but if it hasn't been allowed to complete the tuning cycle then rklopp may be right. Should be no harm in letting it go for a while and see what happens.

Or it could be that the motor being unloaded is "confusing" the vector alogorithm. Try loading it and see what happens.

might be pre flux

im not sure about the drive you have but i know that some vfd preflux the coils with dc. this assists with boosting the start tourqe. with a uncoupled motor and high boost you may be injecting enoght power to get the stator to move this will unset the vfd as it doesnt exspect the motor to turn thus it trys to stop the motor before boosting again. ive seen uncoupled motors jump on the bench as the shaft jerks back and forth. we teach electricains on the bench on how to program the vfds and some settings like start voltage. boost etc is best left to the drive then adjusted slowly. i would surgest recording the settings then reset to factory defaults. try the motor then slowly adjust the settings one at a time. alot of settings like boost start are not realy required to be reprogrammed until you get to machinery that is overloaded to start with. if the motor is coupled to a load then i would look at other things like forwards/backwards switch has high resistance causing it to drop in and out. turning the vfd on while the run switch is in the on position. min speed is set to zero (zero is a bad setting as it will try to run at no speed) ramp up time is way to long so motor trys to run forward and weight of load drags it backwards so vfd trys to stop the load before trying again. i hope something here helps you as its hard to see whats realy going on with out putting a meter on it and seeing what is realy going on.
p.s if all else fails v/f normall works until you can figure out the problem

J Hendrickson, J Lauffer & skirty -
Thanks for your insights. I've gone back to 60 Hz defaults except for setting F05 to potentiometer speed control (=001). Problem remains as initially stated. I am dubious about the preliminary tuning cycle theory for a couple of reasons - when the problem occurs a quick motor off/on (not VFD off/on) cycle always clears the problem, no matter how soon it is done - also when I just leave it to itself, it has never cleared on its own, even when given ten seconds or so to do so.
I'm definitely looking forward to seeing if being loaded makes a difference, but don't want to belt it up to the pump until I've got some hydraulic fluid in the system and don't want to fill the system until I'm thru fooling with piping and valving - it was enough of a mess when I drained it at the start of the project! I'll definitely post info on its response when it is loaded - probably next week.
Again, thanks to all.

This text is taken from the Siemens web pages: Has to do with similar symptom. I have no Idea regarding the TECO drive.

How can I minimise the motor instability when the motor is lightly loaded and controlled by an MM420?
Hide part numberDisplay part numberPart number:
6SE6420.. MICROMASTER 420 - 0.12KW - 11KW
6SE6440.. MICROMASTER 440 - 0.12KW - 250KW
Motor instability can occasionally occur with MM420 on motors operating with light loads; sometimes this will cause nuisance tripping such as F0002.

Usually the gain for oscillation damping (P1338) can be used however its effect is limited because the damping is only active between 5% and 70% of the rated motor frequency.
On a 50Hz supply this gives an effective range of 2.5Hz to 35Hz.

In order to make the damping effective the maximum operating frequency of the motor must be increased by recalculating the v/f curve. By increasing this to 70Hz the range that oscillation damping operates is increased to 3.5Hz to 49Hz.

By increasing the setting of P0304 and P0311 in the same ratio, the range of the damping is increased, but the V to f curve is kept the same

Value of P0304 = 400V + 40% = 560V
Value of P0311 = 1425 rpm + 40% = 1995 rpm

By limiting the Fmax (P1082) to 50Hz and making sure that P2000 = 50Hz the drive will still follow the same v/f curve with the same motor volts and frequency however P1338 is now effective from 3.5Hz to 49Hz. This should solve any oscillation problems.

Failure and Parameter description:

F0002 Over voltage
P0304 Rated motor voltage
P0311 Rated motor speed
P1338 Resonance damping gain V/f

[end quote]

Click to expand...

Cal G - Thanks for your response. The TECO drive I've got seems to lack the sophistication represented by the parameters you cite for the Siemens, or if it has them they are beyond my ability to figure out.
I have completed the project, at least thru all steps needed to make the machine fully functional, and so far find that with the motor belted to the pump (i.e. loaded) the VFD starts it correctly every time in either V/F or vector mode.
Also, I'm finding that since reasonable table motion speeds will probably never require operating below 30 Hz, the vector mode is not really needed. With this drive costing only $131.00, though, I'm just as happy to have it available.
Thanks to all for your responses.

sorry to bring a dead post back up but i have the almost same setup, teco vfd and balador motor. It does the same thing. It rocks back before starting and if stall prevention is on it get to 4hz and just jumps up and down from 3.8-4.2 hz and will never get any faster. With stall prevention off and coast to stop it acts fine.

Did you ever find the problem? Btw i am just bench testing and have not put it on the lathe yet. If this has anything to do with it.

Bugman -
My last post, above, covers my last efforts. Once I found that all was well with a load on the motor, I left it in vector mode and just made chips. Since you are bench testing, I assume that your motor/VFD is unloaded, but will probably behave properly once installed on your lathe.
Good luck
Monoblanco