1N4007GE getting hot at 36mA current draw,

[Kimmen80]

Hello,

We have a few Siemens Sinamics G150 frequency converters here in our ship, and few of them are faulty...
I took one and found the IGBT module to be defective, after taking out the IGBT Module and fault finding it I found a SMD capacitor to be shorted and this lead to a broken rectifiyng diode (SOT-23) series diode. There is one on each each pin on the isolating coil. Some guessing online made me bet on something like this: https://docs-emea.rs-online.com/webdocs/13a4/0900766b813a4618.pdf
As I did not have spare of this diodes I took 4 of our off the shelf 1N4007GE and threw them in..
The IGBT module now works, the voltages are the same on all of the phase controlers...... BUT the 1N4007GE diodes get to hot to touch... only 36mA on 1A diodes.
The only thing I can think of is that the 24V DC-DC 18V isolating cuircut operates on very very high frequency making the 8pF capacitance in the 1N4007 coming into play. The diode I found datasheet on above only have 1pF at 1MHz. If I connect two 9V batteries in series (we dont have a proper powersupply here...) and input them thru the diodes they dont get hot at all, and the IGBT module still works.
I have no equipment to measure the switching frequenzy.

Any thoughts on this matter?

Best Regards
Kim-Andre   

[Gyro]

Welcome to the forum, 

I'm not sure what frequency and rise time that your IGBT drive module is working at, but the first thing that comes to mind is that the 1N4007 is a 'slow' diode, intended for 50-100Hz rectification etc. It could well be that the heat dissipation is coming from its slow Reverse Recovery Time. The easiest test would be to replace it with something faster (eg. UF4007) and see if it then runs cold.

[Kimmen80]

Thank you Gyro,


Yes I agree with you, there must be something with this.
The diodes are not for the 1000V main IGBT cuircut. It is the DC-DC isolator for the control cuircut.
What do you think about using this diode?    https://docs-emea.rs-online.com/webdocs/1074/0900766b810743e9.pdf     It has a reverse recovery time of 4ns compared to the 1N4007 at 2us
I dont have any fast diodes, then i would have to try and salvage some from scrap. We are at sea now

Thank you for the fast response time.

Best Regards
Kim-Andre 

[Gyro]

I dont have any fast diodes, then i would have to try and salvage some from scrap. We are at sea now

Well that could well be a first around here, a genuine rescue at sea!

The SMBD7000 certainly counts as a fast diode. The Vr of 100V and maximum forward current of 200mA (looks more like 150mA in practice) look as if they give a reasonable margin for your requirements (18V, 36mA).

Good luck. 

 Chris

P.S. Double check that the pin-out matches what you worked out when fitting the 4007s - I can't see that from here.

[Kimmen80]

Thank you Chris,

I will give it a go I will update the thread when I have gotten the components and tried. This will probably be about 2 months from now as I am not able to get the components until I go home on my trip off.
I see you are from the UK, we are working at the windfarms outside your shore at the moment

 

Best Regards
Kim-Andre

[Gyro]

Hi Kim-Andre,

Hey, I'm near the South coast, you might not be that far away! 

Yes, please do come back and tell us how it goes, It's always be nice to know how these things turn out.

You now know something else to add to your ship's stores. 

Best Regards,

Chris

[Kimmen80]

Hello Chris,

yes the store is growing, too bad it is always a different type or rated component that say goodbye.
After I came on-board the El-workshop looks more and more like a electronic service shop than the old boring change of el-motor bearing setup.
It's to bad that the "not working throw away" mentality normally rules.
This one converter cost 5800 EUR and they have changed 2-3 of them previously, and as far as I can see the culprit on all of them is ONE ceramic capacitor fail... less than 1 EUR in spare parts    .

On the other converter with same problem there is another channel that is faulty, but I have not been able to take it out and check yet. If it is the same capacitor, but on different phase. I will have to change all of them to be sure it will be a lasting repair.

I did not notice your comment about the pinout on the diode, but it's correct. There is a total of 6 DC-DC supplies on the card one for each 1/2 period on each phase. so I had a few to compare to. The temporary fix gives identical total power draw compared to the others so I am pretty confident this will solve the problem.

I just wish I had better tools for this sort of repairs. I only got a generic temp controlled iron and a fluke... lol, that makes varnish covered SMD electronic repair a bit of a hassle. Don't even got solder wick! but it is on the way already 

We sailed from Great Yarmouth few days ago, and now we are east of Leeds at Hornsea field.

  Again thank you and enjoy the weekend.
Kim-Andre 

[Kimmen80]

Hello,

Update.
It has been a while since I started this post, and I was supposed to come back with info regarding the repair.
The qonverters are still working as they should after replacing the diodes and caps after more than 6 months. We also had one failed with burned driver Mosfet, I ordered similar mosfet with better specs, and this is also working.
Thank you all for the help I got on this matter. 

Best Regards.
Kim-Andre 

[CJay]

Does that mean you're working for Gamesa?

[Gyro]

Hey, Kim-Andre, welcome back!

Thanks for the update, good to hear that it was a lasting repair.  I hope you've had chance to order a selection of useful bits since you were last around, you can only carry marine salvage so far. 

Chris.


P.S. As far as I'm aware, you're still our only rescue at sea!

[Kimmen80]

Does that mean you're working for Gamesa?

Hello CJay,
No I'm not working for Siemens, but we got a lot of Siemens equipment onboard.
At the moment the ship is in Nigeria. Working with not so "clean" energy...

Best Regards
Kim-Andre 

[CJay]

Shame, I was gonna look you up in the directory