Variable frequency drives in mechanical engineering: practical explanations of applications and use cases
VFDs have long been more than just "speed controllers" in mechanical engineering. They are a process tool that turns a rigid mains supply into a variably controllable motor supply – and thus turns "on/off" into a movement that can be specifically adapted to the product, process, and environment. Technically speaking, a VFD converts the constant mains voltage and mains frequency into a variable system of voltage and frequency. This allows the speed and direction of rotation of a motor to be changed in a targeted manner.
What does this mean in practice? You gain more control over the machine, reduce energy consumption where it matters most, and increase process stability – especially with changing loads or demanding environmental conditions. In this article, we highlight the most important applications in mechanical engineering and give you clear guidance on when a VFD is the right solution.
Why VFDs are so often the best choice
As soon as a process does not require permanent "full load," potential arises. This is because a VFD allows you to regulate the motor speed according to demand – and thus often also the energy consumption. This is particularly evident in pump applications: reducing the flow rate by just 10% with a VFD can already lead to an energy reduction of more than 25%. This is why VFDs are becoming the standard solution in many machine designs when energy efficiency, operating costs, and sustainability are crucial factors.
At the same time, drives improve operating quality: smooth ramps during start-up and shutdown reduce mechanical stress. The process runs more smoothly and is reproducible.
The most important applications
Conveyor technology: Controlled dynamics for material flow and cycle operation
In conveyor technology, it is not so much the "maximum value" that counts, but rather controllability: controlled start-up, defined speeds, clean load changes. This applies to roller conveyors as well as conveyor belts or corner transfer units.
A drive ensures reproducible motion sequences, reduces jolts, and relieves mechanical components. Especially in clocked lines or with changing product weights, this stabilizes the material flow – and thus the overall equipment effectiveness.
Winding machines: Gentle on materials and reproducible quality
Winding applications are a classic use case because the spool diameter changes during the process, but the web tension must remain constant.
In practice, the aim is to avoid material damage and achieve reproducible winding. The drive enables stable control of the speed/torque specifications – and thus supports process reliability under changing operating conditions (unwinding/winding, roll change, acceleration/braking).
Pumps: Efficiency and process control in one step
Pumps are a prime example of sensible speed control. Historically, many pumps ran directly from the mains, but the drive enables the motor speed to be adjusted to actual demand. This reduces energy consumption, makes operation more consistent, and eliminates the need for throttling or bypass systems, which often result in energy losses. At the same time, mechanical stress is reduced, which improves service life and availability.
Typical pump applications in mechanical engineering include process and cooling circuits, circulation pumps in plant modules, and pump skids. The combination of control quality and efficiency is a major advantage, especially in applications where flow and pressure vary.
Fans and blowers: Stable air flow, less energy, robust function
Fan and blower applications also benefit from VFDs – both in HVAC-related machine environments and in process-critical air systems. Typical integrated functions for this include PID control, "flying restart," and "power loss ride through." In the case of high-inertia fans, speed reduction can be used for energy recovery to save energy and installation costs (e.g., for brake resistors).
For mechanical engineering, this means that air volumes can be controlled cleanly, operation remains stable, and you get additional diagnostic and process functions that go beyond pure motor operation.
Control cabinet or decentralized? The architecture follows the application
In practice, a key question often arises: Should the drive be located in the control cabinet – or decentralized close to the motor or machine module? Both approaches have their merits. The decisive factors are space, environment, installation effort, and the desired modularity.
Lenze VFDs cover this range of solutions: from ultra-compact control cabinet designs to robust decentralized concepts.
The protec and motec are ideal for decentralized applications. These drives are designed in protection class IP66. The i650 motec, for example, is available for wall and motor mounting, thus offering an optimal decentralized drive solution. It features an integrated Logic PLC based on CODESYS (IEC 61131-3) as well as table positioning for autonomous axes and machine modules. It has four IO-Link ports with limited master functionality and an integrated energy recovery unit, eliminating the need for a brake resistor.