For many types of applications, precise control of speed and torque are decisive in everyday operation. Exact control of speed 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 can provide a considerable energy saving. At the same time, being able to 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 grid to direct current and then back to alternating current with a controlled frequency and voltage that makes the motor run at the desired torque and number of revolutions.
Energy savings of up to 50 percent
By using a frequency converter, you will typically achieve better and more effective control than with hydraulic or mechanical regulation. Instead of having the motor run at full power and using equipment such as , 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 applications, such as centrifugal fans and pumps, this can provide an energy saving of almost 50 percent.
“It is, for example, more energy efficient to control a centrifugal pump by adjusting the motor’s revolutions via a frequency converter than using valves to regulate the volume of liquid. At the same time, this causes less wear and tear, and the converter can also lead to softer start and stop as an alternative to a soft starter,” says Claus Balle Thomsen, Product Manager for Hoyer Drives & Controls.
Connecting link to intelligent control
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 control 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 in the production.
“It is possible to get info like operating hours and energy readings on your laptop, which can, for example, be used to diagnose worn equipment via increasing power consumption. In this way, it is possible to prevent breakdown of an application that needs to be serviced earlier than planned and defer the service of applications that are in good conditions. The converter can also change the motor’s direction of rotation and thereby release a jammed pump if something has become stuck in the pump housing. All these functions can help improve the uptime,” Claus Balle Thomsen explains.
Attend to sources of noise
A frequency converter can either be integrated 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, among other things, generate different types of interference, acoustic noise, harmonic disturbance on the grid and EMC noise, also called electromagnetic compatibility, which can 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 the EMC requirements. For this reason, professional advice should always be sought when selecting frequency converters. A service switch for mechanical maintenance may, for example, be built into the converter as to avoid a typical EMC fault source and, at the same time, achieve savings on installation costs. From Hoyer’s side, we can provide guidance on correct screening and supply the motor with the proper EMC filters so it is ready to be connected correctly together with the frequency converter,” says Claus Balle Thomsen.
Hoyer Drives & Controls – facts
- With the establishment of Hoyer Drives & Controls, Hoyer Motors is now able to provide a total solution that covers both motor and frequency converter.
- Combined motor and VFD solutions from 0.37-1800 kW are offered.
- The focus is on OEM solutions, where the VFD is either integrated with the motor, supplied as a separate stand-alone unit with high protection classes (IP) or cabinet mounted.
- Hoyer Motors is working with leading manufacturers of frequency converters, such as Schneider Electric, Kostal Inveor and Danfoss Drives. Segment-specific solutions are offered.
Find out more about Hoyer Drives & Controls here.