a.In the MPPT form,the process chip is constantly calculating the solar panels output power .It will adjust the motor speed to the best output form to make sure ther water pump can continuous running.The MPPT solar power use ratio is about 90%.The advantage is the pump can continuou running if the solar panels output power is not enough .But the disadvantage is the solar panels out put power change will be 3 seconds delay.

b.When the speed switch is in 100% speed form (Full speed),the solar panels output power is reach the initial power of the pump system continuous running(the MIN.work power),and the pump is in the MAX output power .The advantage is fast reaction to the solar panels and offer the MAX output power to the motor.The disadvantage is the soalr panels output power is less than the initial power of the pump system , the pump start to working will reduce the solar panels output voltage less than the MIN.,the pump will stop working.

c.When the solar panels power is not enough,we suggest to use MPPT form,If enough ,we suggest to use the Full speed.