Hi
I have a 300W inverter that I use for a desktop computer with LCD monitor (not CRT...) and a router and few insignificant loads. The inverter has an overload protection (and overheat and short-circuit protections).
I use it with a 12V 200Ah battery. A 20A charger charges the battery when there is electricity. I installed a relay inside the inverter and wired it as a contactor so when electricity is off the computer (+ router...) they switch to the inverter output..
Everything was working fine till few days ago when something happened when I was outside home but the inverter was ON as always, the inverter failed to start. I tested it and repaired it successfully after replacing about 20 components (power MOSFETs, BJT transistors, diodes, resistors, photocoupler -317 ...)
I didn't used the same MOSFETs but I chose suitable replacements on hand.
Usually, I compare most important parameters to choose I good replacement, but this time while I'm using "vrt-dvd 2009" and looking to transistor FTP18N06 which is used in the inverter and was bad, that software says IRF540 is a good replacement so I used it in place of FTP18N06.
Today the inverter stopped to work. I found that 2 from 4 IRF540 transistors are damaged. I looked for both FTP18N06 and IRF540 parameters and found Id of FTP18N06 is 59A while that of IRF540 is only 30A. Off-course this means that the IRF540 is not a good replacement.
This time I used IRF2807 which has a much higher Vdss and Id and Power dissipation, and much lower Rds(on). One thing I'm not sure about is about the switching speed. These MOSFETs are on the 12V side. There are other MOSFETs on the 220VAC side which have Vdss=500V (FQP13N50C), I replaced them the next time with IRF840. I found one of them shorted this time and replaced it.
No after I replaced the bad components, the inverter is failing to start. The big high voltage capacitor has no voltage across, the rectifying diodes are ok. and the high frequency (ferrite) transformer is ok, and the signals on the gates of the MOSFETs are oscillating at 30KHz (I thought they usually oscillate at a frequency between 50KHz to 100KHz).
The only thing I doubt with is the IRF2807's Gates' and switching characteristics.
Any help or idea is greatly appreciated.
Regards,
Hazim
I have a 300W inverter that I use for a desktop computer with LCD monitor (not CRT...) and a router and few insignificant loads. The inverter has an overload protection (and overheat and short-circuit protections).
I use it with a 12V 200Ah battery. A 20A charger charges the battery when there is electricity. I installed a relay inside the inverter and wired it as a contactor so when electricity is off the computer (+ router...) they switch to the inverter output..
Everything was working fine till few days ago when something happened when I was outside home but the inverter was ON as always, the inverter failed to start. I tested it and repaired it successfully after replacing about 20 components (power MOSFETs, BJT transistors, diodes, resistors, photocoupler -317 ...)
I didn't used the same MOSFETs but I chose suitable replacements on hand.
Usually, I compare most important parameters to choose I good replacement, but this time while I'm using "vrt-dvd 2009" and looking to transistor FTP18N06 which is used in the inverter and was bad, that software says IRF540 is a good replacement so I used it in place of FTP18N06.
Today the inverter stopped to work. I found that 2 from 4 IRF540 transistors are damaged. I looked for both FTP18N06 and IRF540 parameters and found Id of FTP18N06 is 59A while that of IRF540 is only 30A. Off-course this means that the IRF540 is not a good replacement.
This time I used IRF2807 which has a much higher Vdss and Id and Power dissipation, and much lower Rds(on). One thing I'm not sure about is about the switching speed. These MOSFETs are on the 12V side. There are other MOSFETs on the 220VAC side which have Vdss=500V (FQP13N50C), I replaced them the next time with IRF840. I found one of them shorted this time and replaced it.
No after I replaced the bad components, the inverter is failing to start. The big high voltage capacitor has no voltage across, the rectifying diodes are ok. and the high frequency (ferrite) transformer is ok, and the signals on the gates of the MOSFETs are oscillating at 30KHz (I thought they usually oscillate at a frequency between 50KHz to 100KHz).
The only thing I doubt with is the IRF2807's Gates' and switching characteristics.
Any help or idea is greatly appreciated.
Regards,
Hazim