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Registered Member #1811
Joined: Sat Nov 15 2008, 11:52AM
Location:
Posts: 14
Hello guys, I have been given an inverter to fix for a friend. Its a 500W TOHDA inverter. I know they are a pain t fix but im having a go. It stopped working randomly while connected to a new and charged battery with a 150W load on and apparently it was not even hot when it failed. Its blowing fuses when connected to a 12v supply. I checked its mosfets diodes etc to see they are working... Im not really expecting an answer for all this but i decided to check the transformers (it has 2) i desoldered one and im measuring it. The outputs or such they may be are short circuits(when i subtract the 0.6 ohms of my multimeter leads) and the input is 1.5ohms (say 1 ohm if i minus the leads) Is there something wrong here or am i just a newb? Thanks for any help guys
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
This is to be expected, a transformer is just several coils of wire wrapped around some kind of core--so to your ohmmeter they will appear to have a very low resistance. When the inverter drives it at a high frequiency the inductance of the transformer prevents everything from exploding.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
If it blows fuses on switch on then check the main switching traansistor(s) - probably short-circuit...now find what else failed - I'd replace the switcher ic and any small electrolytics nearby, check for burned resistors etc. - good luck.
Registered Member #1811
Joined: Sat Nov 15 2008, 11:52AM
Location:
Posts: 14
Hmmmm thanks for your info guys.. It does not have transistiors it has 4xIRF3250 and 4xIRF740 N channel mosfets which i desoldered one of each group, checked and they are ok. Should i just order a driver IC, replace it and hope for the best? :D (unless anythings wrong with the resistors or zener diodes)
Registered Member #1614
Joined: Wed Jul 30 2008, 03:08PM
Location: Argentina
Posts: 52
an option is to energize the control board with the 12V batt disconected then check mosfets gate waveforms ( frecuency, dead time , etc)with a oscilloscope . the 12V side could be too, may be an antiparallel diode or a capacitor.
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Inverter transformer question
