LSIS (LG) VFD overload "failure" mode

So my main questions is: During a "hard" VFD overload (as stated below; not from a programmed overload detection trigger) is it common that they fault-out in a way that the motor keeps running ? It is as if the VFD fails and lets current pass, but it must still be converting to 3 phase from single...so it's not just that the IGBT's are "ON"/passing current. There is still a conversion to 3 phase.



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Back ground info, see top for the main question;

VFD Model: LSLV0022C100-1N

Inverter works well been using it via Modbus control for over a year.

I was testing how much torque a motor can provide with this VFD and noticed something.

Single phase 220vac @60Hz in, 3 phase out

I'm testing this VFD, manual VFD panel control no modbus , I create a situation where I exceed the VFD's (current) rating.
I set a jog frequency of 10 Hz, I hold the motors shaft still,I turn on the jog switch, the amps climb and then the VFD is overloaded (as expected).

Now during this, the VFD is overloaded and inoperable .(until reset)..although the freq and other readouts seem to work in real time (60 Hz). No panel buttons work except the reset button I have wired in. The VFD is in some kind of "Limbo" state as expected, the unexpected part is that the motor runs instead of power being cut to it...

During this I release the shaft. The motor is un-stalled and starts to runs at 60 Hz indicated on the VFD DRO(not the 10 Hz target speed ) the stop button will not stop the motor, but the RESET button WILL stop the motor...it does reset the VFD and let in function normally again and so stop the motor.

NOTE: Normally I do have appropriately set overload protection settings programmed in to prevent an overload that will disrupt the VFD's operation..this was just something I noted during a test.

If I understand you, you have a case where there is an overload, but the VD keeps trying to run the motor.

Yes, that mode exists.... in some VFDs.

The VFD simply limits current to a safe level for itself, and keeps driving the motor. Normally you have a programmable choice of a hard fault off, or this, or other actions.

Is that what you mean?

@ JST:

Nope, as described, say the frequency is at 10 Hz during the test. When this overload happens, the VFD controls no longer work (except reset) and the motor then runs at 60 HZ (not 10-hz anymore). (60 Hz is be "line frequency" but of course it is 3 phase out from the VFD, and single phase into the VFD...so it's not just passing "raw" line electricity in to the out=side.)

As mentioned It is a "severe"/hard overload as I have the programmable overload triggers set to where they are not preventatively activated for this test.

That is usually something that you can select in programming; what you want it to do in the case of an overload and/or stall condition. Your choices are often Trip, which is usually the factory default, or you can tell it to Current Limit, in which case it backs off on the output frequency to try to reduce the loading on the motor. This sounds like the action of a Stall, where the VFD detects that the motor is not moving, so it is current limiting. If left like that for a long time, it will probably trip.

Thanks, yes (as described in the original post) I can program all of those settings to *programmatically* create a SOFT "trip" to actually prevent the HARD fault that I am describing. The SOFT (programmed trigger will STOP the motor and display an error on the DRO , all that is good and expected.

What I am talking about is a HARD fault where where the SOFT (programmed triggers) do not prevent/protect the VFD (due to parameters that are set too high etc. In this "ultimate"/hard failure mode one would still expect the motor to STOP (no power applied) rather than run , at 60 Hz ...an increase in speed from the set frequency in this case. ALso there is NO ERROR displayed on the VFD , it just still display the real time frequency. The VFD is "in Limbo" in this state as no controls work (except hard reset) and it is not indicating that i knows of any fault/error, though clearly there was one.

All this is described in the original post, just recapping here.

OK, I was extrapolating because I have never seen the "speed up and try hard" overload case.

Agree with jraef, that should be settable. It's an odd sort of setting, though.

When I say "hard fault", I mean a fault that stops operation of the VFD and requires a reset.

When I say "soft failure", I mean something that continues to apply as much power as it can without going over current limits. That is a useful settg for many cases, since it eliminates the need to manually reset anything, and recovers as soon as the problem is removed.

What you described seems like a hybrid, where it finds an overload, times out on the accel, and then decides to go up to nominal "motor rated speed", even though it was not supposed to go that fast. I am not seeing a case where I would want that.

Is that by chance an "HVAC" type VFD? Those may have special fault modes for "smoke clearing", etc, where the VFD just has to keep working if there is any way possible to do so. Somewhat like "fire pump mode" motor controllers.