With the release of the new FREQROL Solar Pumping VFD inverter drives series, being the FR-E700-E12 and FR-D700-E12 series’, some information is required in terms of the comparison with the standard FREQROL inverter drives series.

This article will provide some clarity on the differences.

Standard VFD vs Solar VFD

What are the differences between a standard inverter drives and the solar inverter drives?

What does the solar drive offer extra?

This series of drives were designed to make intelligent decisions, being applied to fluid reticulation systems at a remote location, taking the external process variables and conditions into account. (these are configurable by the user via inverter parameterization). This field is known as solar pumping.

Intelligent optimization and independent remote decision making are the factors of this game.

The following is applicable;


Also known as the Output current detection Function.

It is a function that allows the VFD to either stop or continue operation when the inverter changes to a dry run state. This state is identified when zero current is detected.


This function enables the inverter to operate automatically without waiting for the user to turn on its switch.

This function is dependent on the status of the inverter’s DC bus voltage.

The time frame for the automatic operation starts can be adjusted, based on the level of the minimum operating voltage due to unstable power supply.


The inverter has the capability to monitor fluid reticulation flow rate from the pump, based on the motor shaft rotational velocity. This allows the inverter to monitor the flow rate.


This function enables the inverter to operate at the maximum possible output frequency, based on the load characteristics for pump operation, when the DC bus voltage is low.

DC Bus Undervoltage?

 Energy can not be created out of nothing.

When the inverter detects a DC bus Undervoltage level (when the DC bus voltage drops to a certain predefined level), the inverter stops safely, and displays “UV” error message.

Restrictions compared to Standard inverters
  • In the case of the FR-E700-E12 series, built-in options are not to be used.
  • Automatic restart after instantaneous power failure functions is not available.
  • Main circuit capacitor life measurement functions are not available.
  • Offline auto-tuning will not be completed properly if the DC bus voltage is equal or lower than the valve determined by (even if the motor operation is possible)