VSD (VFD) Not powering up when power is applied - Help

Howdy folks

Just wondering if there's someone out there who's had this same issue i'm having.

Customer purchased a machine with a SEW Eurodrive VSD(VFD) fitted, the machine was powered up several times this morning with no issues, this afternoon the machine was powered up everything work except VSD, checked incoming power all fine - 3 phase @ 430volts present as it should be yet unit was not powering.

Rang SEW support who told me if not powering then the drive is fried, not sure how it could be when all the other 3 phase components are working fine. So went out and purchased an ABB VSD with matched specs, checked incoming 3 phase volt before powering up the new drive - all good, powered the new drive up and nothing, unit didn't even light up on the front panel, again checked incoming volt and all was correct.

Check both manufacturers manuals but no help on this problem.

Anyone have any ideas to why this is happening?

Any help would be appreciated.

Thanks in advance

Do you have power on the DC bus?

Most drives power the control circuits from the DC bus.

Alan

Silly question, how do i check the DC bus? i normally check dc bus via display panel but cant as its not powering up, I'm actually still onsite.

Thanks for reply

I don't know about your drives but some drives have a DC+ and DC- on the main power terminal strip, otherwise take the cover off and see if you can find the DC bus capacitors, depending on the size of the drive it could be one or many capacitors but they will be large.

Alan

If you have no power on the DC bus then the SCR front end is not working.

Stupid Idea: Disconnect the cable to the motor !! and power the vfd.

Do you have the wiring diagrams for the machine?

and what about the model of the ABB drive?

Strange how these subjects seem to come up at once, this was posted earlier today. you can see the DC Bus on here.

Thank for your input so far guys.

Never had this issue before so bit of a mind bender. Just baffled why 2 drives not working at all.

Alan/Badger

No DC-/DC+ on either drive, I'll pull them apart in the morning.

nonuke

First thing i did, also removed all other cabling except mains input. Also connected the motor its was running to a DOL contactor just to test it was working, all was good.

JohncCalderWood

Ya actually i have a copy of the wiring diagram for the machine.

ABB VSD is ACS310-03E-02A6-4
SEW VSD is MC07B008-5A3-4-00

Well i've left site and in my hotel room and all the pubs are shut WORST DAY this month

What type of mains supply do you have powering the drive? If it is a resistive grounded neutral it is possible you cooked both drives.

The common denominator appears to be input power, or lack of it, or 2 failed drives for no reason.

Is the drive protected by fuses? Remove, and test them. Is it possible they're being back fed by another load,
appearing to be good? Try powering the drive/s from a different 3 phase source.

Never had this issue before so bit of a mind bender. Just baffled why 2 drives not working at all.

Click to expand...

I have seen something similar, and it also started with a SEW motor. The customer's contractor installed and burned three different $3500 VFD drives. When I was called, I went to the motor terminal box and checked the connections. I did not even have to megger the wires, as the problem was obvious. This SEW motor had screw-terminal connectors. The sloppy electrician had left whiskers on the stranded wires that were causing a short-circuit that destroyed each of the 3 replacements drives as it was turned on.

The instruction manual has special instructions for connecting the drive to floating or corner-grounded three phase power. Did you follow those instructions? If not, and you have that kind of power source, you have likely burned up the CE noise filter section in the drive and destroyed it. The CE noise filter requires a balanced-to-ground (grounded wye) power source or it has to be disconnected before powerup.

holyhobgoblin,

you say that 3 phase 430V was there ok, was that to the input terminals of the drive?
What fuses are fitted (if any) for the the 3 phase supply to the drive? Are they OK?
I once worked on a system where the drive was only powered up when an enable contactor was energised first before 3 phase was fed to the drive, then it waited for the start signal, so usually the E-stop was pushed in if the drive hadn't powered up.
Anything obvious in the circuit from the drawing?

If it was working then suddenly not, and you know for sure that you have your 3phase power at the line terminals of the drive, then it can only be that there is something about your incoming supply that is destroying the front end of these drives the instant the power hits them. That typically points to the issue raised about the fact that drives are designed to be objected to solidly grounded Wye (Star) systems, without resistance grounding, and not Delta power systems. Drives with CE filters, and even some without, have an MOV network protecting the rectifier components. If that network presents a lower resistance to ground than a grounding resistor, or in the case of a delta source, the only path to ground, it can destroy the MOVs immediately and leave the rectifier subject to the next surge. Generally that scenario doesn't happen as immediately as you are indicating though.

I would hazard to guess that you have a similar effect caused by a different issue, extreme common mode noise, in fact so severe as to present zero-cross notching of significant duration that is then causing immediate current surges through the diodes, frying them immediately. That kind of severe notching is often created by older DC power controllers, and sometimes older style AC controllers, that used what are called "GTO thyristors"; GTO stands for Gate Turn Off, meaning an SCR that can be forced into a premature off condition rather that being allowed to self commutate.

Another thing that can do that is open transition Star-Delta motor starters, especially on motors with high torque requirements at the moment of transition. What happens is that during the open transition, the brief loss of motor torque allows the motor to slow down just a bit. Then when reconnected in Delta, residual magnetism in the motor keeps it in Regen mode and the difference in speed means it is out of synch with the line frequency. So that is like trying to parallel two generators out of synch, resulting in a current spike of up to 2200% of the motor rating, which easily damages other nearby electronic components.

So in your commissioning process, the first few times you energized the machine, whatever is causing this was not connected to the line yet. But once it was, it is immediately killing your AC drives. Go through your commissioning sequence looking for that scenario. It's just a swag, but one I have unfortunately run in to more than once.

Thanks for the replies guys.

Before leaving site last night, both drives where taken to the customers other factory and powered direct from a 3 phase suuply there, but neither showed any signs of life. So drives must be dead.

The motor was checked for shorts all OK, i connect motor to a DOL contactor to test it and motor ran no problems.

Here in Australia i think most incoming supplies are TN-C-S earthing system, but is called MEN (multiple earthed neutral) instead of PEN.

I checked the earth back to the sub-board and couldn't find any issues, check between earth and each phase showed 240 volts meaning there is a earth connection back to the neutral link at the main board.

The motor is only .55kw with the VSDs being 0.75kw rated, and both can accept up to 480 volts input.

I've sent someone out to get me a single phase input instead of a 3 phase input to see if that works. Other than that i'm completely stumped.