AC200 cooling fans

I have just received my AC200max. Under load (150w) only the fan at the ac/dc input end comes on and is not that quite. Is this correct and does the second fan only come on under higher loads?

@BFJ , The two fans of AC200MAX are intelligently adjusted according to the power. Only one rotation is not broken, when the power with load is greater than 1500W both fans will start.
I hope the above will help.