This article describes applications of variable frequency drives(VFDs). A variable frequency drive (VFD) or inverter is a controller for electric motors commonly used in electromechanical drive systems. Its main function is to regulate the speed and torque of the induction motor, varying the motor input frequency and controlling the corresponding voltage or current changes depending on the topology.
Variable frequency drives are being widely used, and their common applications are well-known and easy to implement on-site. But, the design of specific applications that solve specific problems is no longer so simple.
When we understand the load requirements, using a VFD for a specific application is not a mystery.
In industries where industrial frequency drives are especially important, a few applications of an industrial frequency drive are presented below.
- Process control (pressure and flow regulation)
- Elevators and hoists
- Motors and converters for winches
- Pumping
- Compressors, blowers, and pressurizers
- Cranes
- Cooling towers
- Reduction of potentially explosive atmospheres
VFDs are great energy-saving devices and give good returns on investment. VFDs are nowadays used in every industry because of the ease of process control and energy savings.
Applications of Variable Frequency Drives in Industries
VFDs are widely used in the following industries.
| Industry/Application | Textile Industry | Paper Industry | Wood Industry | Food and Beverage Industry | Automotive Industry | Chemical Industry | Metallurgy Industry |
| Bobbin Winder | Feeders | Saws | Conveyors | Conveyors | Centrifugal Pumps | Injectors | |
| Texturing Machines | Folders | Material Conveyors | Agitators | Wind Tunnels | Crunchers | Stitch Seam Welding Machines | |
| Weaver’s Loom | Assembling Machine | Oven Conveyors | Dough Machines | Deburring Equipment | Dosing Conveyors | Metal Finishing Treatment | |
| Knitters | Printing Press | Washers | Mixers | Grinders | Packaging Machines | Plastic Covering Machines | |
| Presser Frames | Ink Pumps | Grinders | Crunchers | Fans | Agitators | Press and Cutting Machines | |
| Carding Machines | Cutting Machines | Transfer Cars | Screw Pumps | Ventilating | Container Handling | Steel Rolling Machines | |
| Beam Wrappers | Packaging Machines | Chip Conveyors | Transporters for Freezing Tunnels | Pumps | Mixers | Wire Drawing Machines | |
| Conveyors | Glue Pumps | Pumps | Fans | Hoists | Granulators | Fans | |
| Washers | Unwinding Machines | Fans | Cutting Process | Parts Positioning | Dosing and Metering Pumps | Pumps | |
| Twister and Doubler | Cutting Machines | Ventilating | Wrapping Pumps | Shears | Fans | Conveyors | |
| Extruder | Conveyors | Labeling | Welders | Crushers | |||
| Mixers | Coating Machines | Capping Machines | Pressers | ||||
| Gear Pumps | Winding / Unwinding Rollers | Filling Machines | Feeders | ||||
| Dryers | Dryers | Boring / Cutting Machines | |||||
| Transporters | Centrifugal Pumps | Transfer Lines | |||||
| Ironer | Crushers | Tool Changers | |||||
| Dry Cleaning | |||||||
| Washing Machines | |||||||
| Cutting Machines | |||||||
| Screw Pumps | |||||||
| Bag Handling Machines | |||||||
| Scrappers | |||||||
| Printing Machines | |||||||
| Flocking Machines | |||||||
| Sewing Machines | |||||||
| Picking Machines |
Now, we will discuss the major applications of VFDs.
Applications of industrial frequency Drives
Process control (Pressure, flow regulation)
There is also potential for improved control in many process industries by using VFD/pump combinations. PID algorithm in frequency drives eliminates the use of PLC and can control process pressure and flow regulation as done with a control valve. The speed control of the induction motor can achieve flow control, and energy saving is an added benefit.
Elevators and hoists
The level of security required by elevators makes the installation of an industrial frequency inverter almost mandatory. The speed of the elevator motor can be controlled precisely, and the motor runs smoother with VFD.
Jerking problems due to excessive acceleration or deceleration are almost eliminated with the use of VFD, and the entire mechanism becomes silent and cushioned.
The start and stops of the elevator are more frequent, and it experiences stress at the start if operated on DOL. The VFD reduces the stress on the motor at the start, so VFDs are used in elevator applications.
Motors and converters for winches
The marine industry needs VFDs. These drives are specific ones. Some Direct Torque Control (DTC) programs offer the advantage of removing the necessary motor encoders or load cells. This is how another benefit is obtained: these components are reduced, and maintenance is saved. In addition to working with winches, the converters also work with anchors, moorings, trailers, and gate ramps.
Pumping
Through a VFD, upon starting a pump, it initially applies a low voltage at a low frequency to the motor, hence avoiding high inrush currents. The VFD then increases the applied voltage and frequency at a controlled rate to speed up the charge without drawing too much current. This starting method allows a pump to develop rated torque while drawing rated currents.
The water, oil, and gas industries widely use VFDs for pumping applications. In the extraction processes, high-powered motors are used, and the operation must be smooth and optimal.
Compressors, blowers, and pressurizers
Compressors perform various functions, from powering pneumatic tools on assembly lines to refrigeration and air conditioning. The main application of the converters in these appliances is to reduce their maintenance, and, most importantly, it is used for enormous energy savings.
Optimizing compressor and motor performance can reduce stress on the mechanical and electrical components of the compressor system, thereby reducing wear and tear to avoid failures.
Applications of Variable Frequency Drives in Cranes
For businesses that depend on the handling and movement of materials, it is necessary to have control of- precision, reliability, speed, and safety. With an industrial frequency inverter and a PLC system, it is achieved.
Frequency drive is widely used in crane control for optimum operations. Many special functions are available. It has a wide range of advantages, including reducing load sway and more precise control of movement, etc.
Cooling towers
For cooling towers, a direct drive motor and speed converter are helpful in order to maintain a constant pressure and temperature of the water for cooling a stream of boiler water by partial vaporization through the exchange of latent heat of dry and cold air that circulates through a cooling tower.
Thus, the drive shaft, gearbox, and induction motor can be replaced in industrial refrigeration. The fact of having fewer parts is, again, an advantage for the maintenance of the system. Risks are also minimized.
Reduction of potentially explosive atmospheres
The mixture of explosive vapors, gases, particles, or dust with air forms explosive atmospheres. Depending on the substance, it will take more or less to create it. Some elements seem innocuous but, in large quantities can pose a health problem and turn an area into a dangerous one.
Certain considerations must be taken when choosing the industrial frequency inverter as well as the motor in which it will be coupled to maximize its safety—for example, isolation.