A customer has asked us about VFD some time ago. This is Delta's VFD007M21A. Since we don't have a product from this brand, we recommended Eaton's DG1-324D8EB-C20C to it. Here I introduce Variable Frequency Driver and soft starters, and their differences.

What is VFD?

A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. VFD is suitable for a wide range of multi-pump and fan applications. The six mainstream brands of VFD are ABB, Allen Bradley, Schneider, Toshiba, and Hitachi.

What is a soft starter?

A motor soft starter is a device used with AC electrical motors to temporarily reduce the load and torque in the powertrain and electric current surge of the motor during start-up. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network, extending the lifespan of the system.

What is the difference between VFD and Soft Starter?

Soft starters are often used in motors that are vulnerable to large inrush currents, while VFD can control and change the speed of the motor. VFD and soft starters are usually used with PLC or AC motors. The functions of VFD and soft starter are basically the same. VFD is dominant in speed control, and soft starters are advantageous in size and price. The VFD can change the speed of the motor, while the soft starter only controls the starting and stopping of the motor.

How to choose VFD or Soft Starter?

If your application has high inrush current requirements but does not require speed control, then you can choose a soft starter directly. If you have speed control needs, you can choose VFD. Soft starters are usually smaller in size than VFDs. If the soft starter is installed now, and the need for speed control is determined later, the VFD can directly replace the soft starter, vice versa.