Variable Speed Drives Supplier: Know the Engineering Behind These Products

March 24, 2023

With the rising demand in industry to reduce energy consumption, the variable speed drive (VSD, also known as variable frequency drive, VFD) has emerged as a vital tool for doing this in ordinary industrial applications. Let’s look at where motor control technology used to be and where it is now.

Motors have been an established element of the daily operation and manufacture of products, from the original AC versions to today’s contemporary plants. Before VSDs, AC motors were controlled by connecting the motor to an electrical AC source. To regulate the speed of the motor, a mechanical system was used to take the rotational motion and modify the output based on the requirements of the manufacturing machine. This arrangement is frequently referred to as a gearbox.

About Variable Speed Drive Products

The first VSD was born as knowledge and understanding of power electronics expanded, and the technology linked with it evolved. It was considerably different from the VSDs used in modern factories today, but there were some essential parallels. They work similarly, albeit with analogue control rather than the digital operation we see today.

Fast expansion in the world of microprocessors fuelled great technical improvement in the VSD, propelling it past the analogue period and into the new digital world, resulting in a device that can not only drive a motor but also have its intelligence. VSDs have since improved, become quicker, and smaller, allowing them to be employed in various industries and applications.

How Variable Speed Drives Function

Inside the power electronics of the VSD, we will examine three main components separately: the input bridge, the DC Link, and the output bridge. The alternating current source enters the input bridge, where a diode bridge rectifier transforms the alternating current into a direct current. The current is then normally smoothed by a DC capacitor bank; however, if the drive is rated beyond 2.2 kW, an inductor is used to smooth the supply current. After that, the DC voltage is stored within the DC Link before entering the output stage, which has three pairs of insulated gate bi-junction transistors (IGBTs). Older versions would have needed MOSFETs or thyristors to achieve the same result. The output stage then switches on and off the IGBTs, which ‘chops’ the current to the right frequency. This is accomplished by a procedure known as Pulse Width Modulation (PWM). Because the PWM generates a triangle waveform with a sinusoidal nature, the motor will continue to drive normally because it only sees the sine wave.

How Variable Speed Drives (Vsds) Save Money

Consider a DOL motor with speed control regulated by a gearbox. The motor will continually operate at full speed, consuming the greatest power. Consider replacing the gearbox with a variable speed drive (VSD) to adjust the speed of the motor. The motor will not have to operate at maximum speed, and the gearbox will slow the system. Rather, the variable speed drive may change the frequency or speed of the motor by modifying the PWM inside the VSD’s output stage. This implies less power will be drawn from the electrical supply, resulting in increased efficiency and cheaper expenses. A 15 kW motor may often save up to 5,700 kWh when compared to utilising the motor without a VSD. Considering that motors account for 65% to 70% of total power utilised in industry, it’s easy to understand how adding VSDs into these motors may result in significant savings.

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