IRFP7430 vs IRFP7430Pbf - 7430 Failure

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nh19926
Level 1
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First reply posted First like given First question asked

My home inverter died.... has been running fine for 7 months, then some of my IRFP7430 went bad and fried.  I am looking for a replacement but only find IRFP7430-Pbf.  The ones I am using in my home inverter are N-Channel Strong IRFET's.

Take a look at my pics... do not understand what happened after 7 months of use.  Looking for a drop-in replacement and possibly a better quality IRFET without any redesign.

Help is appreciated.

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Shivam_P
Moderator
Moderator
Moderator
100 replies posted 250 sign-ins 50 solutions authored

Dear @nh19926 ,

The comments from @cynic_bandera makes sense regarding the possible causes behind the failure of the FETs.

Nevertheless, The FETs IRFP7430 and IRFP7430Pbf have same electrical specifications, They just differ in the Orderable Part Numbers.

Hence IRFP7430Pbf could be used as a replacement for the IRFP7430 from the electrical specs point of view.

Regards

Shivam

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cynic_bandera
Employee
Employee
10 questions asked 50 solutions authored 25 likes received

I suppose your invertor is 12V input voltage. The issue in my opinion connected with a wrong design.  I see the source bonding melting and thermal management issue. I see many companies make bad engineering, thermal, mechanics and physics are extremely important (reliability)! I'm an old stile and conservative engineer (reliability is number one). My comments:

1. One TO247 can handle up to 75A (look at an International Rectifier 20 years ago article) ! They try to take 110A current. It leads to the failure... In this case the right engineering solution would be more MOSFET paralleling and current distribution. 

2. Thermal management. One thermal isolator has roughly 2.5K/W thermal resistance. One MOSFET dissipates about 45W so 112°C overheating...The solution is to increase number of MOSFETs, using better thermal interface with lower thermal resistance.

I suppose If you change the MOSFETs it will happen again and again...

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Shivam_P
Moderator
Moderator
Moderator
100 replies posted 250 sign-ins 50 solutions authored

Dear @nh19926 ,

The comments from @cynic_bandera makes sense regarding the possible causes behind the failure of the FETs.

Nevertheless, The FETs IRFP7430 and IRFP7430Pbf have same electrical specifications, They just differ in the Orderable Part Numbers.

Hence IRFP7430Pbf could be used as a replacement for the IRFP7430 from the electrical specs point of view.

Regards

Shivam

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