# Snubber part is heating and transformer is giving audible noise

#### mohan.n2293

Joined Jan 23, 2017
60
Hi Guys ,

We designed a power supply for 3phase ,but the issue here is we are facing huge noise in the transformer and snubber part is getting heat even with the input voltage 200V AC.

One issue i found is when i measure my transformer leakage inductance(using LCR meter by shorting all secondary at a common point)i got 56uH but as per the PI recommendation leakage inductance should be 30uH.

Please find the attachment for schematic ,drain to source voltage and transformer design details.

Mod edit: moved from duplicate post. One per question, please.

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#### mohan.n2293

Joined Jan 23, 2017
60
Hi All,

I have designed a power supply in which at lower loads transformer will be in normal condition as load increases snubber will starts heating and transformer gets more heat.

Please provide suggestions to solve the issue.

#### Janis59

Joined Aug 21, 2017
1,383
1)Check the shift between HL and LL sides of bridge. Sometimes the sys controller may be designed for some 100 or 300 kHz works very badly on slower circs like 10...30 kHz, providing unsatisfactoru dt. Then at smaller power it LOOKS fine but the system is balancing on sharp edge of burning down Your 900 Amp igbts. As I have success to repeat this many times, I may tell that You will cach the moment with ears, and network fuses of say 5 Amps will not be demolished inspite there were flow thousands and thousands to coock a transistor brick
2)Check the braiding for all the signal forming circs. The kiloamperes per microsecond generates a dU=di/dt fantasmagoric teravolt spikes what be sensed in tens of meters afar, but if at design You have been not enough thought how to make a circ insensitive about those spikes by briding, metal boxes, orthogonal placing, groundworks position digging etc etc, then symptoms may be exactly similar to those You tell.
3) look at India journals one month before today was the article on my surname on 100 kW power supply, probably some ideas may be useful.