Further info on the inverter board I bought
(see post
http://www.anotherpower.com/board/index.php/topic,1116.msg12138.html#msg12138)
The EGS002 board is configured to NOT soft start (JP6 is shorted) and the dead time is set to 500ns with JP3 and JP8 shorted as supplied
by the inverter board manufacturer.
I already had two EGS002 boards purchased from ebay 6 or 12 months ago. These 2 boards are identical in function.
I immediately swapped one of the ebay boards for that which came with the inverter board to see if I have 2 spares or not and it worked perfectly.
The ebay boards came with soft start enabled and some other dead time setting than 500ns.
The "standby switch" as shown on the aliexpress product page is in fact the inverter "on/off" switch. This is handy to have.
By the way, no instructions or documentation came with the inverter board. So I saved the aliexpress page to pdf.
I captured a couple of screens from the DSO when first switching on the inverter output with the soft start disabled.
(again using the 50VA desklamp load on the secondary)
These may help us understand why a soft start is to be preferred when driving a large toriod.
Look at the high voltage change rate - it must place large strains on the FETs when you attach a large load on the secondary and do a hard start.
Blue is secondary voltage (approx 240V RMS, using a high voltage differential probe)
Yellow is DC supply current, AC coupled
Purple is a gate drive for the PWM low leg (it needs to be referenced to the DC supply's 0 volts - only got one diff. probe alas)
Light Blue is primary current via a current transformer.
first shows a short period where I enabled the inverter output. Already the DC bus caps on the board were fully charged.
I think the DC input draws a large ripple content. Maybe in the finished project I might find some big-ass low ESR bulk caps to be placed just before the board's DC supply terminals. I recall reading how lead acid batteries do not like loads with large ripple content.
next is a close up of the PWM when switching off. It seems to me that there is some soft stop effect going on.
I now show the hard start up. I think this may be where we can easily blow these nice big FETs to tiny pieces if we are not careful.
Last is the entire event showing hard start, run under constant load and stop.
I intend to do a higher power test this weekend. I think I will change it to use a soft start from now on.
I hope this is interesting for you here. If not, tell me and I will just stick to the build of the inverter system.