Full control and optimised operation with frequency converters

Lower energy consumption and more precise control of speed and torque are just some of the advantages of using a frequency converter to control an electric motor.


For many types of application, precise control of speed and torque are decisive in everyday operation. Exact speed control can, for example, be necessary to adapt a conveyor belt to the rest of the process, and the ability to adjust the output of a pump in relation to the need can save a considerable amount of energy. At the same time, being able to precisely control speed can improve the working environment by dampening noise and vibrations and reducing mechanical stress on the motor.

A frequency converter, also called VFD (Variable Frequency Drive) will often be the optimal solution for regulating the speed of an application driven by an electric motor. The frequency converter transforms the alternating current from the electricity network to direct current and then back to alternative current with a frequency and voltage that makes the motor run at the desired torque and number of revolutions.

Energy savings of up to almost 50%

By using a frequency converter, you will typically achieve better, more efficient control than with hydraulic or mechanical regulation. Instead of having the motor run at full power and using tools such as dampers, valves or gearing to control speed and torque, a motor connected to a frequency converter consumes exactly the amount of energy the process requires. In certain types of application, such as centrifugal ventilators and pumps, this can provide an energy saving of almost 50%.

For example, it is more energy efficient to control a centrifugal pump by adjusting the motor’s revolutions via a frequency converter than using valves to regulate the quantity of liquid. At the same time, this reduces wear and tear, and the converter can also soften the starting and stopping process as an alternative to a soft starter,” says Claus Balle Thomsen, Product Manager, Hoyer Drives & Controls.

Connecting link to intelligent management

Another significant advantage of frequency converters is that they can be adapted to collect data such as temperature and vibrations from the motor via sensors. These can be used to monitor the condition of the motor and pave the way for more intelligent management of the applications and preventive maintenance. This also makes it possible to monitor operation via a cloud solution and, in some cases, troubleshoot without being physically present at the plant.

“It’s possible to see data like operating hours and energy readings on your laptop, which can be used to diagnose worn equipment via increasing power consumption, for instance. In this way, it is possible to prevent the breakdown of an application that needs to be serviced earlier than planned and postpone service on applications that are running fine. The converter can also change the motor’s rotational direction, thereby freeing up a jammed pump if something gets stuck in the pump housing. All these functions can help improve uptime at customers’ facilities,” Claus Balle Thomsen explains.

Take care of noise sources

A frequency converter can be either be fitted together with the motor (see video) or connected via a cable. During installation, it is important to be aware of a variety of different issues. A frequency converter can generate different types of interference, acoustic noise, harmonic reactions on the network and EMC noise, etc., also called electromagnetic compatibility, which can also affect radio equipment and data transfers.

“Interference from a frequency converter should be limited via filters and screened cables so that the installation can comply with EMC requirements. For this reason, professional advice should always be sought when selecting frequency converters. For example, a service switch for mechanical maintenance can be built into the converter to avoid a typical EMC fault source and, at the same time, save on installation costs. On Hoyer’s part, we can provide guidance on correctly screening and supplying the motor with the proper EMC adapters so that it is ready to be correctly connected to the frequency converter,” Claus Balle Thomsen says.

Drives & Controls

Establishing Hoyer Drives & Controls enables Hoyer to provide one combined solution that covers both motor and frequency converter.