How to select a VFD for your motor

A variable-frequency drive (VFD) is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. A variable frequency drive is a specific type of adjustable-speed drive. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, microdrives or inverter drives. Since the voltage is varied along with frequency, these are sometimes also called VVVF (variable voltage variable frequency) drives.

To select a VFD,  you need to know below data,  which you can read on the nameplate,  of your motor.

The VFD specification should meet, at least meet the above data of your motor. Normally we suggest a class bigger.

Please see an example below:

To make sure you select the right model of VFD, we shall pay attention to the loading type and rated current.

Normally we call the water pumps and fans light duty loading, hoisting and crane heavy duty loading, and mostly we call normal duty. the difference between them mainly are light duty loading dose not need large torque from the motor, but heavy loading need large torque at low speed especially the hoisting machine needs large torque all the time.

• For light duty loading,  we advice you choose P5/V8/M,  so the 37kw 380V inverter with model P5-37T4,  whose rated current is 75A. if your motor is 75A,  a grade large will better.
 
• For heavy duty loading,  we advice G7/G11/V5 series,  the 37kw inverter with G7-37T4,  whose rated current is also 75A,  but can output large torque at low frequency.
 
• Normal duty you can choose 303/V8 series,  37kw inverter 303-37T4,  whose rated current also be 75Amps.

Commonly we advice one grade larger while choosing the VFD, or at least you make sure the rated current of your motor is smaller than rated current of the VFD.

Please note that the current of your motor is the key point in selecting a VFD.

More question, please contact with our technical and send us the filled data sheet above.. GANDO provides free consultant related to our products.