“If my motor operation looks normal, why would I use frequency inverters?” Good question!
As some of us are informed, frequency inverters are used in any operation in which there is mechanical equipment powered by motors. The inverters provide extremely precise electrical motor control, so that motor speeds can be ramped up and down, and maintained, at speeds required. Thus, it utilizes only the energy required, rather than having a motor run at constant speed and utilizing an excess of energy.
Since motors consume almost all of the energy produced, the control of motors, based on demands of loads, increases in importance, as energy supplies become ever more strained. Additionally, end users of motors can realize 25 – 70% energy savings via use of motor controllers.
Among the most successful strategies managers have at their disposal for controlling electrical energy use and minimizing utility costs is the use of frequency inverters. Incorporating frequency inverters into applications such as fans, pumps, and cooling towers can reduce energy use.
Here 5 beneficial functions of a frequency inverter:
1. Controls starting current — When a normal powered (AC) motor is started “across the line,” it takes much time to gain power to start the motor and load. This power activates the motor windings and produce heat, which will eventually reduce the endurance of the motor. A frequency inverter starts a motor at zero frequency and voltage. As the rate and voltage “build,” it “magnetizes” the motor windings, which typically takes 50-70% of the motor full-load current. Additional current above this level is dependent upon the connected load, the acceleration rate and the speed being accelerated, too. The substantially reduced starting current extends the life of the AC motor, when compared to starting across the line. The customer payback is less wear and tear on the motor (motor rewinds), and extended motor life.
2. Controls acceleration — A frequency inverter starts at zero speed and accelerates smoothly on a customer-adjustable ramp. On the other hand, an AC motor started across the line is a tremendous mechanical shock both for the motor and connected load. This shock will, over time, increase the wear and tear on the connected load, as well as the AC motor. Some applications, such as bottling lines, cannot be started with motors across the line (with product on the bottling line), but must be started empty to prevent breakage.
3. Adjusts operating speed — Use of a frequency inverter enables improving of a process, making changes in a process, allows starting at reduced speed, and allows remote adjustment of speed by programmable controller or process controller.
4. Controls motor “stopping” — Just as important as controlled acceleration, controlled stopping can be important to reduce mechanical wear and tear because of the shocks to the process or loss of product due to breakage.
5. Saves energy – Frequency Inverters operate only with the necessary power, rather than having the motor function at fixed speed and utilizing a surplus energy. Using a fixed speed motor would require some type of mechanical regulating device, such as a vane or damper; but the fact remains that the motor would still be running full load and full speed (full power). Energy savings can be sufficient to pay back the capitalized cost in a matter of a couple of years or less, depending on the size of the motor.
Developments in frequency inverter technology are putting even more power in the hands of maintenance and engineering managers, who are taking a closer look at the life-cycle costs and potential benefits of this device for their facilities. Thus, it is a great advantage to use frequency inverters in enhancing all motor powered operations.