1.5KVA POWER INVERTER FOR HOUSEHOLD EQUIPMENT.

The inverter doesn't "stand by" at all. If you want power when there is no utility power available, you need a UPS (Uninterruptible Power Source), which is a converter, inverter and battery backup source. Standby time is dependent upon how much battery storage capability you buy. You can bu a 1.5kVA unit with 6 minutes, or you can buy one with 6 days capacity.

"Domestic" means nothing without a context of where you are located.

Inverters can be had over-the-counter at caravan and marine equipment outlets, as well as a myriad of internet sources. There is no need to design.

Equipment on standby represents an uninterruptible power supply. These can be had from top-of-the-range computer equipment suppliers, as well as a further selection of internet sources. There is no need to design one of these either.

With the purchase comes the manufacturer's warranty, which is more valuable than the time spent in designing the above from scratch.