VFD Faults

Does the VFD indicate what it is "faulting out" on? Over load? Over voltage? Under voltage? Stall? You have to give us something to work with here.

Generally, things like this tend to be commissioning errors, i.e. you have programmed something incorrectly or failed to program something necessary for the application.Do you know what you are doing with VFD programming or did someone just throw this on there and expect it to work?

What is the fault error. It should say on the VFD, or a sequence of blinking lights that states in the manual.

And when does it fault?....start-up (ramp-up), after its been running, you need to give us something more.

Sorry for the limited information. I was able to further discuss the issue with the Electrician, and I will be able to test on the weekend. In my initial post I mentioned that a power source was connected, however, it happens to be an ELR (Phoenix motor starter). The ELR faults out after 5 seconds of the system running. After the ELR is reset 5 to 6 times, then it will work for 4 to 5 hours and then the fault happens again. The VFD shuts down because the ELR does not supply anymore power. Keep in mind, when the VFD is by passed the system works fine. There is not error codes on the ELR.

It is somewhat unusual to use a motor starter ahead of VFD. What features does it provide?

It is more common to use a 3 phase contactor.

Not knowing the specs of your "ELR" starter it may be it cannot handle the harmonics that the drive presents to it.

Input reactors are often used ahead of VFD's to help mitigate some of the harmonic issues.

Give us a single line of your system from the main transformer through to the motor with part numbers (or links to the parts) and we may have more than opinions to offer.

VFD =3 phase 480 V 60Hz

Motor=68Hz

To me it seems that the VFD will fall out because the frequency of the VFD and the frequency of the motor are not the same. The motor frequency should be set at 60Hz.

No sir,

VFD means Voltage/Frequency Drive, and it's also called Frequency Inverter, in the VFD you control the speed of the motor by the variable freuency and usually it ranges from 0Hz to 200Hz depending on the application and the motor windings, so that is not the problem here.

for Taki , u still didn't give us the fault code that u have either on the VFD or on the motor starter,and i agree with the people who say u don't need this starter as it can cause conflict.

No idea what "ELR" stands for.

I can guess maybe it's some sort of Electronic or Solid State Overload Relay? If so most, if not all, are unsuitable for use with VFDs, whether on the input or the output. The reason is, they typically cannot properly deal with the harmonics created by the VFD and the RMS current readings are thrown off. All modern VFDs now provide motor overload protection themselves, so if you have one ahead of it, it is redundant and unnecessary. Remove it and let the VFD do the motor protection.

Please see the link below for the ELR Motor Starter.

http://eshop.phoenixcontact.no/phoenix/treeViewClick.do;jsessionid=LGLVrQmWMMwtBBz0hYGGqJllVnwC21PBZZYjSwVMzLM2wVNxGTdP!-144951299?UID=2297060&parentUID=852411055&reloadFrame=true

Your help is appreciated with such limited information. I will get the error code on the ELR at the latest tomorrow when I am able to test.

Thanks,

I have the ELR fault codes and they are as follows: Symmetry - The two motor currents deviate by more than 20 %. OR Phase failure - One of the two measured motor currents is zero or the phase shift between the two motor currents does not equal 120°, but 180° I hope this helps, and thanks again

Don't use the ELR ahead of the VFD.

If you want backup then use a simple contactor for the VFD, then if the VFD is out of commission use the ELR.

The drive will look after itself and the motor if set up properly.

Normally a VFD should not be started and stopped via the three phase power.

Taki R,

I agree fully with the recommendations by the others. I suspect that if you were to discuss this with Phoenix Contact, they would also concur that their ELR cannot be used on the input (or the output) of a VFD. Because the VFD begins with a diode bridge to convert the incoming AC to DC, its load on the AC input line is not linear. That means that its input current waveform is not in a direct relationship to the input voltage waveform. Until the input voltage of the sine wave exceeds the DC bus voltage, negligible current is drawn. Then it turns off again when the input voltage on the sine wave drops below the DC bus voltage. Therefore, the current waveform appears more like a series of square wave pulses, with the spacing between them increasing and the pulse widths decreasing when the VFD load is lowered. If there is no filtering on the supply side of the VFD (such as with line reactors), this pulsed waveform imposes on the supply a large amount of harmonic noise, with the total harmonic distortion easily exceeding 500%. The monitoring electronics on the ELR are not programmed or designed to see this as noise; they see it as a faulted load.

I am not at all surprised that the ELR is thinking there is some sort of fault on the load. There is---a design application fault. The applied load is not what the ELR was designed to feed. Early failure of the ELR is very likely; The VFD will probably survive.

Get rid of the ELR---every function it provides can be provided directly by the VFD. If your application must have a line side contactor, provide a magnetic one not an electronic one.

Your question to this discussion board is a good one to ask. I (and the rest, I am sure), greatly appreciate your fast responses to our requests for more information. Thanks--John M.

I agree. REMOVE that ELR immediately! Using a solid state contactor like that in front of a VFD is setting up a race to see which one fails fastest, the consequences of which can be a loss of the VFD input rectifier. There is NO NEED for that device in the circuit anyway. The VFD will provide superior motor protection and is fully capable of reversing the motor on it's own. In fact, if you reverse the input phasing to the VFD it will have no effect on the motor direction anyway, the VFD is simply rectifying the incoming power. Relative phase rotation of the supply is completely irrelevant.

One of the possibilities is a loose or open link inside the motor terminal box (got the T-shirt - it's now on a well-known internet auction site) . If one of the links goes open circuit than the phase currents will go out of balance, and under those circumstances it would be quite in order for the <...VFD...> to say "Sorry - I'm not playing".