How do you size a VFD? Darwin Motion

Posted on 17th Nov 2023

Darwin Motion Drive

Sizing a Variable Frequency Drive (VFD) involves determining the appropriate capacity or rating of the drive for a particular motor or system. Darwin Motion VFD & Servo Drive Manufacturer share the general steps to size a VFD:

Determine Motor Power (HP or kW):

Identify the power rating of the motor in horsepower (HP) or kilowatts (kW). This information is usually available on the motor nameplate.

Consider Motor Load:

Consider the type of load the motor is driving. Different loads (e.g., centrifugal pumps, fans, conveyors) have different characteristics, and this can affect the selection of the VFD.

Determine Voltage and Frequency:

Verify the voltage and frequency of the power supply. VFDs are designed for specific voltage and frequency ranges.

Calculate Motor Current:

Calculate the full-load current (FLC) of the motor. You can use the formula:

IFL=Pmotor3×Vline-to-line×Power factorIFL​=3

​×Vline-to-line​×Power factorPmotor​​
where PmotorPmotor​ is the motor power, Vline-to-lineVline-to-line​ is the line-to-line voltage, and the power factor is usually provided on the motor nameplate.

Consider Overload Conditions:

Take into account any overload conditions or applications that may require extra torque or power.

Select an Oversized VFD:

It's common to select a VFD with a rating higher than the calculated motor current. This provides a safety margin and ensures the VFD can handle variations in load and potential future upgrades.

Check Compatibility:

Ensure that the selected VFD is compatible with the motor type and load characteristics. Different VFDs are designed for specific types of loads.

Consider Additional Features:

Evaluate the features offered by different VFD models, such as communication protocols, advanced control options, braking capabilities, and protection features.

Environmental Conditions:

Consider the ambient temperature and environmental conditions where the VFD will be installed. Some VFDs may require additional cooling or derating in certain conditions.

Consult Manufacturer's Guidelines:

Always refer to the manufacturer's guidelines and specifications for both the motor and the VFD. They often provide specific recommendations for pairing their products.Darwin Motion offers Micro Drive- Matrix 900, DR Matrix 350 / Solar Drive, High Frequency Drive - DR Matrix 500, High Performance Drive - DR Matrix 680, Regenerative Drive - DR Matrix 880

Keep in mind that these are general guidelines, and the specific requirements may vary based on the application and manufacturer. If in doubt, it's advisable to consult with the VFD manufacturer or a qualified electrical engineer for a more accurate sizing recommendation.