Solar panels provide a DC current, however, so an inverter, or Variable Frequency Drive (VFD), is necessary for conversion. While running, a water pump will need different amounts of power depending on the amount of water available for pumping and the amount of water needed. A VFD changes the frequency and voltage of the AC current to compensate for the motor’s variable workload. By using an AC variable speed controller called a Variable Frequency Drive (VFD) , the pump motor will have the proper voltage and current. The trick is to supply DC from the PV array directly into the DC bus inside the VFD.

As the sun rises and PV voltage and current increase, the VFD will accept the input and when the power is high enough, it will start the pump. The PV array must be large enough to provide enough power to start the pump with including the head of water. This is a 2HP VFD which can be used to drive existing water pumps or new solar water pumps (AC based) of upto 2HP. VFD acts as a bridge between the submersed water pump and the solar panels used to power them. VFD is a standard model which is configurable with all makes of water pumps available in India. It has a LCD display as well.