The type and characteristics of backup loads decide the power capacity of the FHP system and whether the loads can work normally. FHP capacity configuration requires the starting current of home loads ＜ LRA value of FHP system.
Typical home loads fall into two categories:
• Surge load (large starting current), starting current is about 3 to 7 times the rated current when running.
• Pure resistive load (small starting current), starting current ≤ 1 time the rated current. For example, take an FHP system with rated power of 5kW is installed. When the grid power supply fails, there is no sunlight, the generator is not running, and the FHP is in backup mode. When a 3-ton air conditioner turns on, the inrush current from the FHP system will go up to 84A (4 times larger than the rated working current of FHP system). Since fixed-frequency air conditioners can have a long starting period, it may very well trigger the overcurrent protection of the FHP system, which would cause the home loads to lose power.