This inverter bobbin shuts down welding current , can it be fixed ?

[EEstyleZ90]

Trying to fix this inverter ring transformer :

 

[MrAl]

Hi,

What do you mean by 'fix', what is wrong with it?

 

[ahsrabrifat]

You did not mention what is the problem with this transformer. However, this video may help.

 

[EEstyleZ90]

Hi,

What do you mean by 'fix', what is wrong with it?

i suspect it is shorted , and shuts down output current and voltage , everything else in the electronic welding inverter have been replaced !


so maybe i can rewind it ?!

 

[EEstyleZ90]

You did not mention what is the problem with this transformer. However, this video may help.

it is switch mode not linear and after fixing a broke leg i suspect it is drawing too muck output current , resulting in low current and low voltage.

also the current indicator keeps getting down to zero after turn on ! like from 250 A gradually down to zero , also voltage is always low at 1.8 v dc , should be 60 v dc .

 

[MrAl]

i suspect it is shorted , and shuts down output current and voltage , everything else in the electronic welding inverter have been replaced !


so maybe i can rewind it ?!

Oh wow. Well then it depends where the short is inside the windings.
Sometimes the short is near the outside because something physical may have struct the outside, but if it is deep inside then all the later windings have to be removed and the short repaired, or possibly rewind the whole thing. It could be tricky. You have to make sure to wind it the same way with the same type of wire(s) and with the same number of turns.

I once fixed a microwave oven MOTOR that way. Inside the motor windings were open so no current flow. I was lucky though as I took the windings off one by one, it was not long before I got to the defect. There were so little windings removed that I did not bother to replace the windings I took off, just used the new wire end as the connection point for the power. It worked for years after that.

Could your windings have an open section instead of a short?
Also, can you be absolutely sure it is the transformer and not something else heating up?

 

[EEstyleZ90]

Oh wow. Well then it depends where the short is inside the windings.
Sometimes the short is near the outside because something physical may have struct the outside, but if it is deep inside then all the later windings have to be removed and the short repaired, or possibly rewind the whole thing. It could be tricky. You have to make sure to wind it the same way with the same type of wire(s) and with the same number of turns.

I once fixed a microwave oven MOTOR that way. Inside the motor windings were open so no current flow. I was lucky though as I took the windings off one by one, it was not long before I got to the defect. There were so little windings removed that I did not bother to replace the windings I took off, just used the new wire end as the connection point for the power. It worked for years after that.

Could your windings have an open section instead of a short?
Also, can you be absolutely sure it is the transformer and not something else heating up?

I checked electrolytic capacitors 400v 470 uF, replaced oscillator UC3846N , checked all semiconductors , checked switching signal with oscilloscope everything fine, also checked small current trasformer attached to the suspected faulty transformer. .

but when i was checking this transformer , one of the winding legs was cut off , soldered it back but it still shuts down the output current as i said , so i need eather replace or rewind the transformer .

it is also very difficult to unsolder it from the PCB , the legs are thick .

May call it a day and ask the owner to take it back.

 

[ChrisP58]

Trying to fix this inverter ring transformer :

Is the transformer shown here your part? Or is it a similar picture you found online?

 

[EEstyleZ90]

Is the transformer shown here your part? Or is it a similar picture you found online?

Its just similar

 

[MrAl]

I checked electrolytic capacitors 400v 470 uF, replaced oscillator UC3846N , checked all semiconductors , checked switching signal with oscilloscope everything fine, also checked small current trasformer attached to the suspected faulty transformer. .

but when i was checking this transformer , one of the winding legs was cut off , soldered it back but it still shuts down the output current as i said , so i need eather replace or rewind the transformer .

it is also very difficult to unsolder it from the PCB , the legs are thick .

May call it a day and ask the owner to take it back.

Hello again,

Oh then if you can't get it off the board then there is no chance of fixing it, unless it is just a solder joint or something simple like that.

I will say though that it would be rare for the transformer to go bad unless the design was faulty from the beginning. I worked in this industry and have seen transformers actually melt. The insulation inside melts and drips off and the converter shuts down. That only happens when the design is not right though.

This makes me wonder how long you have had this converter and how long did you run it before a problem came up?

These devices are simple in theory but in practice there are a lot of intricacies to consider. If you can return it for a refund or whatever that could be the best option.

 

[EEstyleZ90]

Hello again,

Oh then if you can't get it off the board then there is no chance of fixing it, unless it is just a solder joint or something simple like that.

I will say though that it would be rare for the transformer to go bad unless the design was faulty from the beginning. I worked in this industry and have seen transformers actually melt. The insulation inside melts and drips off and the converter shuts down. That only happens when the design is not right though.

This makes me wonder how long you have had this converter and how long did you run it before a problem came up?

These devices are simple in theory but in practice there are a lot of intricacies to consider. If you can return it for a refund or whatever that could be the best option.

Hi , it's not mine , a client brought it for repair.

So what could be the problem after fixing the leg.
Is there a troubleshooting procedure to follow ?

I will repair it just for knowledge purposes.

 

[MrAl]

Hi , it's not mine , a client brought it for repair.

So what could be the problem after fixing the leg.
Is there a troubleshooting procedure to follow ?

I will repair it just for knowledge purposes.

Well then it would come under a general repair procedure. That would mean checking the power supplies first, then signals, then power components, then the transformer. To test a transformer, you have to run it up and measure current and voltage.

A trick that is often used for troubleshooting converters is to power the low voltage section with an external power supply, then for the main power buss that gets powered normally, except the input voltage is raised slowly. That slow increase in input voltages allows testing usually before anything goes badly wrong (fuse blow, breaker trip, transistor burns up, etc.).

I'm not aware of anything you had fixed in the past but it would be similar to that, except for the gradual increase in input voltage test outlined above.

Nigel Goodwin still does a lot of repair work maybe you can ask him for some tips too.

 

[Tony Stewart]

If you cut the tracks or remove with solder sucker, or wire fine braid, can you measure the isolation and winding resistance with a CC power supply? If the insulation is broken on the magnet wire, that's a problem that requires replacement.