ATMEGA16/32 based single microcontroller inverter with battery charger

Hi santoshaxl,
The transformer is rated at 800W power and is a standard transformer used for 800W inverters over here. I don't know about the details as I got it wound by an acquaintance who is an expert in making such transformers. The primary voltage is 12-0-12, secondary voltage is 0-140-280.
This inverter has short circuit protection. It uses the fact that during a short circuit, DC bus voltage significantly decreases. The microcontroller senses that and indicates short circuit.
Reverse voltage protection isn't provided as it's connected to the battery 24/7.

Tahmid.

Tahmid said:

Hi santoshaxl,
The transformer is rated at 800W power and is a standard transformer used for 800W inverters over here. I don't know about the details as I got it wound by an acquaintance who is an expert in making such transformers. The primary voltage is 12-0-12, secondary voltage is 0-140-280.
This inverter has short circuit protection. It uses the fact that during a short circuit, DC bus voltage significantly decreases. The microcontroller senses that and indicates short circuit.
Reverse voltage protection isn't provided as it's connected to the battery 24/7.

Tahmid.

Click to expand...

hi Tahmid
ur transformer is rated at 800W power or 800VA power & transformer core size ?

hi Tahmid ,
thanks i got but didn't get core size ?

Hi,
sahu,
It's rated at 800W.
santoshaxl,
I'm not sure about core size, but I'll see if I can find out.

Tahmid said:

Hi,
sahu,
It's rated at 800W.
santoshaxl,
I'm not sure about core size, but I'll see if I can find out.

Click to expand...

800watt means 1000VA if ifeancy is 80% ,if ifeancy is 90% then o\p =889W. i'm right ?
how much current with full load ?

Hi,
Yes, that's 800W of output power. At 90% efficiency, 800W = 889VA
I haven't really measured current at full load, but as a rough guide, I can run an 80W ceiling fan, 40W fluorescent lamp and PC (around 200-300W) for about 2 hours with a 70Ah battery before the unit signals low battery.

Tahmid.

hi Tahmid
can you give me the current consumption when the inverter with no load condition ?

Hi,
It's around 1.4A. I've noticed that efficiency goes up, the more load you apply.

Tahmid.

hi Tahmid
Do you know how to reduce that current consumption in no load condition ? any idea?

Hi,
Yes, one way is to sense the current consumption and shut down when there is no load. But that has its own problems. I don't think 1.4A is bad for an 800W inverter. It's mainly due to the transformer. A smaller transformer would consume less as I saw.

santoshaxl said:

hi Tahmid
Do you know how to reduce that current consumption in no load condition ? any idea?

Click to expand...

use The primary voltage is 13-0-13, secondary voltage is 0-140-250.
its prectical,i'm useing it.
try it sure........

sahu said:

use The primary voltage is 13-0-13, secondary voltage is 0-140-250.
its prectical,i'm useing it.
try it sure........

Click to expand...

as per Tahmid actual calculation the voltage is 10.3-0-10.3(10-0-10) primary , 0-120v-240v sec, if you keep 12v or 13v you can't control the output volt since the cutoff is 10.5v

Hi,
Yes. If you have 10.5v, the output would become (250/13)*10.5 = 202v, not 220 or 230v but maybe acceptable. That's why I used 280v at secondary.

Tahmid.

hi, Tahmid,
what is the minimum volt need to start charging ( 140v?)

i am using 12-0-12v , 0-140-240v transformer if no output regulation
and 9.5-0-9.5v , 0-140-240v transformer if output regulation
i keep m cutoff at 10v

Hi,
That can be changed with coding. Right now, it's set at around 150-160v.

Hello Tahmid,

I just want to know the battery type & rating of the battery. How are you charging the battery?
The other quetions is what is i/p voltage range for ur project? I mean what voltage ur project works.

Regards
Chanchal Chauhan

---------- Post added at 13:27 ---------- Previous post was at 13:23 ----------

Have u tested battery charging life time ? How many days continous u have tested ur project.

Regards
Chanchal chauhan

hi Tahmid
yes i think battery charging protocol is also most important part / did you use constant current charging,constant voltage,trickle charging etc .In sukam they use five step battery charging procedure .could you kindly elaborate battery charging system used in this inverter?

Hi,
Yes, the battery charging part. My one isn't as complicated. It's a simple charger that doesn't charge the battery to absolutely full charge, but maximum charge so that it can provide optimum backup and good battery life.
The battery is charged at around 16A when near full discharged and charge current slowly decreases to about 10A when battery is near 13.5v, when battery charging is completely terminated to prevent gassing or oxidizing of the plates.
The battery charging is phase angle control based and the charging is stopped every 13 seconds when battery voltage is checked. Then charging is resumed again. I initially implemented trickle charging but later discarded it as I found it unnecessary in this case, because whenever battery voltage falls charging is again resumed for a few minutes to make sure battery is fully charged, or at least apparently fully charged.
I've had the test unit running for 8 months, but the final version as shown in the pictures has been running for about 6 months. The battery has never become hot. Moreover, it was about a year old when I started using this inverter. The battery hasn't inflated yet and provides good backup. I don't even have to replace the water frequently, so that shows that the water isn't vaporizing.
I'm using a 12v 70Ah battery. As mentioned earlier, I can run a 40W fluorescent lamp, 80W ceiling fan and computer (around 250W when not at 100% load) for about 2 hours before the unit indicates low battery. From there it takes about 6-7 hours to fully charge the battery and the charging termination to become stable. Usually after running the inverter with 80W fan and 40W lamp, it takes an hour to get it to full charge.
The unit is designed for 150-250v.

The charging current changes with battery rating. The values mentioned are for 70A battery with initial charging current set manually.

Tahmid.

.

---------- Post added at 16:02 ---------- Previous post was at 15:14 ----------

sahu said:

hi Tahmid
ur transformer is rated at 800W power or 800VA power & transformer core size ?

Click to expand...

Re: ATMEGA16/32 based single microcontroller inverter with battery charger
Transformer Wattages depend upon core size and quality(kind) of core.
I remember an old type of core,s formula,
(CORE SECTION AREA*5.6)*SQUARE=WATTAGE Of transformer.
for example babon size of a transformer is 2*2 inch.
We can say core section area is 2*2=4 inch.
Now we can calculate wattage according to formula as above,
4*5.6=22.4*22.4=501.76 watts
But small transformers have 85% efficiency(efficiency also depend upon core,s quality).
We also can measure core size,although a transformer is completed.
As a transformer consist of many laminated foils,
These foils we insert in plastic or fiber babon from both sides one by one.
Now measure complete bundle of these foils of a assembled transformer.
one dimesion is cleared,
For second dimension measure complete length of foil from top.
And divide it by3.
If length of foil is 6 inch,you can say core size is 2 inch.
Now question that this inverter is 800va or 800 watt.
We need to measure amps of battery during inverter mode.
Increase out put load gradually till output voltage remain 230.
when output volts decrease from 230,stop increasing load.
Measure battery volts and amps,multiply them=your inverter,s max wattage.

what's the ideal trans ratio of CT for stabilizers ?