Inverter problems

to stressed out Engineer; darrenabrown

What is happening to these inverters,

Are you getting overcurrent errors, burning out all together???

I don't know what kind of power system you have. I will tell you our scenario, we have a High resistance Grounding sytem Gounded Y Power system. Our Allenbradley drives required a jumper in the power system be removed before applying power. Could you tell me What kind of drives and power system?

I would document everything that is done anywhere in the place and compare the list each time you have to replace one. What is attached to that inverter ?

What repairs. welding near by, electrial repairs near by, anything that could run excess voltage or spike the system in some way. Also watch your input to the inverters for spikes.

Are you by chance using VFDs for any of your motors.

Some VFD have poor filtering and can cause havoc in the power lines. We often find VFD on air conditioners destroying inverters and other sensitive electronic equipment on board.

Hi SOE,

An engineer is not an Engineer if he/she is stressed out. So Buddy, get your spirits high and knock-down the problems before the problems knock u down... Give a strong try with the mind-set to predict problems before they could occur.

Running a facility without Ground / Earthing is against the safety regulations and is detrimental for human beings on the machines as well us for the machines.

Since Inverters use high frequency power switching circuits, running these without Earthing can result in misfiring of the Power devices (IGBTs, MOSFETS, B.Transistors) as well as Control Logics. Please get the Earthing done, it's not very expensive especially with Chemical earthing being around.

If possible, just let us all know which section of the Inverter Fails and what components are failing to enable us direct your investigations suitably.

Regards

Sanjeev

Thank you for your input, I have done a bit of digging this morning and have discovered that we are using the armoured cable as our earth via the glands, so we do have an earth system all be it a very poor one. I have also discovered that the inverters that are going down are Telemacanique, I am awaiting a response from our supplier regarding what damage is being caused to the drives. Once I have this I can then point you all in the right direction. Please bear with me as I have only just started work in this factory and I need to get up to speed.

Hope to hear from you soon.

Regards.

One thing to note is what kind of grid, I will assume a Y Grounded System, It is critical that all drives have the PE terminal Grounded and the Earth Terminal Grounded and checked, We had issues with some of our drives and we found that the installer did not scrape off the back plate which was painted. A very sound earth connection is needed. Also as one of the Gentlemen spoke of earlier a Ventilation system to these is critical if they are mounted in a drive cabinet. We have programmed our PLC to monitor the drives and start and stop the ventilation at the temp rises to a start point of about 100 this reduces a good amount of our drive failures, the other issues are regular PM's cleaning and connection checks.

WHAT ? A factory without earthing system ??? And you are only interested in the life of an inverter ?

PLEASE first have a GOOD (and TESTED) earthing system installed. After your personel's life is not endangered anymore, THEN let's talk about inverters, right ?

Thank you for your input, I have done a bit of digging this morning and have discovered that we are using the armoured cable as our earth via the glands, so we do have an earth system all be it a very poor one. I have also discovered that the inverters that are going down are Telemacanique, I am awaiting a response from our supplier regarding what damage is being caused to the drives. Once I have this I can then point you all in the right direction. Please bear with me as I have only just started work in this factory and I need to get up to speed.

Hope to hear from you soon.

Regards.

Hello,

first you need to have earthing sistem, it is many reasons for that , some of them is - security of people in the factory,also it is useful to made normal work of electronic circuit,PLC,inverters and itc.

You need to tell as what kind of problem you have?

First get earthing sorted out

If vfd runs motor normally then most failures I have seen have been either overheating - this may not affect unit when running but when system is powered down the unit becomes a heat soak, or long cables between the vfd and the motor without a choke.

Thank you for your input, I have done a bit of digging this morning and have discovered that we are using the armoured cable as our earth via the glands, so we do have an earth system all be it a very poor one. I have also discovered that the inverters that are going down are Telemacanique, I am awaiting a response from our supplier regarding what damage is being caused to the drives. Once I have this I can then point you all in the right direction. Please bear with me as I have only just started work in this factory and I need to get up to speed.

Hope to hear from you soon.

Regards.

How on the earth are you operating your electrical systems in your factory with out an earthing system please tell us. if except your inverters all other electrical are working OK please lets know who is your electrical designer and How your installation was certified safe by the electrical inspector who certified we need to relearn electrical engineering from these engineers

crm

Thank you for your input, I have done a bit of digging this morning and have discovered that we are using the armoured cable as our earth via the glands, so we do have an earth system all be it a very poor one. I have also discovered that the inverters that are going down are Telemacanique, I am awaiting a response from our supplier regarding what damage is being caused to the drives. Once I have this I can then point you all in the right direction. Please bear with me as I have only just started work in this factory and I need to get up to speed.

Hope to hear from you soon.

Regards.

Thank you for your input, I have done a bit of digging this morning and have discovered that we are using the armoured cable as our earth via the glands, so we do have an earth system all be it a very poor one. I have also discovered that the inverters that are going down are Telemacanique, I am awaiting a response from our supplier regarding what damage is being caused to the drives. Once I have this I can then point you all in the right direction. Please bear with me as I have only just started work in this factory and I need to get up to speed.

Hope to hear from you soon.

Regards.

I doubt that failure is connected with the poor earthing on a symmetrical supply. Inverter failure (not tripping??) is usually associated with misapplication, poor control design etc relative to the inverter design. The failure mode will give clues as to potential problems, random failure mode will point more to the equipment than the installation / use. If you can indicate what type of failure e.g. blows fuses / cb's, output transistor failure etc this will help.

Also, are there trip records that will assist in diagnosis. Other than temperature, which needs to be inside the design tolerance of the inverter, most other applications can easily be accommodated if outlined when arranging how to control the inverter so as not to cause any problems

first of all u need to get the earthing work done.that is very essential.u can opt for the isolation transformers having ratio 1:1.this would solve the problem of spikes in the supply and would provide smooth supply.

There are many potential solutions but these are 'scattergun' without assessing the primary problem and planning forward from this point - without this information we are just throwing 'bits' at the problem to try to resolve.

Obviously, good earthing is a fundamental requirement in any static control system from a safety and EMC viewpoint. I doubt (not dismiss), however, that this impacts largely on the site inverter problems experienced. Whether transformers or MOV's, chokes, new drives or control system modification are needed depends on the assessment of the problem in the first place (hence the request for more information about the 'failures').

Most problems are easier to cure than diagnose but a litle information can go a long way.

j

I would try the proper voltage MOV's across the inputs. I have worked in industrial electronics for 35+ years and have found voltage spikes are solid state electronics enemy. Nowadays most manufacturers have some protection, but I don't know what vintage yours are. A filter of sufficient current carrying capacity will help. Put MOV's at the input and output of them.

Place the MOV's across the inputs (A-B-C-A) and from each leg to ground (6 qty.) Measure the voltage to ground so the proper MOV's can be implemented there. I have seen some strange readings to ground. This could also aid in troubleshooting the problem.

The Isolation transformers are a good idea and should have electrostatic shielding, but it is an expensive option. I'd try the cheaper ideas first.

Grounds are a good start, but how do you get a good ground in a 30 story building? No ground is better than a bad ground with ground loops. A ground rod at the drive cabinet and all ground wires ran to one point is best.

I have had problems when drives are on the same circuit with large switched loads. Running a separate feed as far back as possible to the source helps much like having a filter.

Heat and contamination is also a killer, especially if it is conductive material. A Preventive Maintenance program may be in order for your factory. A Line Disturbance Analyser would aid the troubleshooting if you could rent or buy one. There are some real bargains on Ebay at times. Dranetz is one brand.