Mastering the Mechanics: A Comprehensive Guide to Variable Speed Drive Controls


Understanding variable speed drives (VSDs) is crucial in many ways. A solid understanding of VSDs enables you to make intelligent decisions about their use and potential benefits. Energy efficiency, cost savings, improved process control, and reduced environmental impact are just a few reasons why (VSDs) are crucial for you and your business and everyone. 

This blog article will dive into the mechanics of Variable Speed Drives, from their workings to the different types of VSDs, their benefits, real-world applications, and smart tips for choosing the right VSD.

Let's dive in!

What is a Variable Speed Drive?

Variable Speed Drives control the energy flow from the power source to the motor. They help regulate the speed of an electric motor by varying the voltage and frequency of the power supplied to the motor, allowing precise adjustment based on what is required by the process.

Using VSDs is critical in industries like manufacturing to ensure accurate and reliable control over their machinery, allowing safe and disaster-free operations. They are often used in various applications, such as conveyors, elevators, and pumps.

How does Variable Speed Drive Work?

A rectifier converts the electrical power that goes into the drive from alternating current (AC) to direct current (DC). The DC power then goes into capacitors that help smooth out the electrical waveform, creating a clean power supply for the next step. From there, the power flows to the inverter, which converts the DC power back to AC power. This output AC power then goes to the motor.

Using VSDs, your business can save considerable money through reduced energy use, maintenance costs, and decreased scrap waste.

Variable Speed Drive Diagram

Types of Variable Speed Drives

Three main types of variable speed drives are DC, Eddy Current, and AC Motor drives. All these types come with an electric motor and a speed control unit. While older variable speed drives used mechanical parts that resulted in failure over time, modern drives used solid-state electronic components.

DC Motor Drives: 

DC drives, also known as DC Motor Speed Control Systems, control motor speed through armature voltage or field current. However, most systems today have been replaced with AC motors and variable-speed drives due to their lower cost and higher efficiency.

Eddy Current Motor Drives: 

An eddy current drive uses a fixed-speed motor and a clutch with adjustable rotors to regulate speed. However, they are less efficient than other drives and are becoming obsolete. Few manufacturing facilities continue to use them, and repairs are often expensive or impossible.

AC Motor Drives: 

AC variable speed drives (VSDs), Variable Frequency Drives (VSDs), inverters, and more are used in various industrial applications such as pumps, compressors, lathes, and production lines. By retrofitting older DC motor speed control systems with AC variable frequency drive systems, significant energy efficiency improvement opportunities can be achieved in industrial manufacturing.

Manufacturers are upgrading to AC variable speed drive systems due to their reduced cost, smaller physical size, and improved performance. This technology helps businesses save money on their power bills, increase quality control, decrease production downtime, and improve efficiency.

Benefits of Using Variable Speed Drives

Variable speed drives (VSDs) can bring numerous benefits to businesses. Let's take a closer look at them:

Save Energy and Money: 

VSDs can significantly increase energy efficiency in many applications. Traditional motors run at a constant speed, even when the output required is lower, causing unnecessary energy waste, especially when the load varies. VSDs adjust the motor speed to match the demand. They can reduce energy consumption by up to 50%, leading to substantial cost savings on energy bills.

Reduce Maintenance and Waste:

VSDs can reduce maintenance costs and waste. Running motors constantly at full speed can wear them out quickly, resulting in costly repairs or replacements. VSDs allow motors to run only at the necessary speeds, reducing wear and tear on motors and extending their lifespan. They also improve process control and efficiency, which can reduce waste.

Benefit the Environment:

The energy savings provided by VSDs have a positive environmental impact. Energy production is one of the largest sources of greenhouse gas emissions, so anything that reduces energy consumption can help to mitigate climate change. By reducing energy use, VSDs can help decrease greenhouse gas emissions and contribute to sustainability goals. Moreover, VSDs can help minimize the environmental impact of industrial processes by reducing waste.

Applications of Variable Speed Drives

Examples of Industries Where VSDs are Used

Variable Speed Drives (VSDs) find applications across different industries and areas. Some industries that use VSDs are manufacturing, oil, and power plants. In manufacturing, VSDs are commonly used to control the speed of machinery and equipment such as lathes, extruders, and mixers. VSDs are also used in various applications like pumps and compressors in the oil industry. In thermal power plants, VSDs find usage in a variety of applications. VSDs are also used in irrigation systems to control pump speed and ensure the right amount of water is delivered. 

Real-World Examples of VSD Usage

Real-world examples of VSD usage include pump systems, where VSDs help adjust the speed of the pump based on demand, resulting in significant energy savings. Fan systems also use VSDs to adjust fan speed based on need, reducing energy consumption and noise emissions. Conveyor systems use VSDs to adjust the speed of the conveyor belt based on the load, improving efficiency and reducing wear and tear.

Choosing the Right Variable Speed Drive

When selecting a variable frequency drive (VFD), it is crucial to choose the appropriate one to avoid potential issues. 

Operating Conditions

The VFD should withstand conditions such as temperature, cooling air supply, gas, moisture, and dust. Therefore, it is vital to choose a drive with enclosures and protective features suitable for these conditions.

Base Speed

The VFD's base speed should be determined based on the required motor speeds from minimum to maximum. Choosing a drive that can handle this speed range is essential, and the allowed amount of speed variation is also a consideration. Depending on the application, necessary speed regulation, such as constant speed at all torque values or tolerating variations, will vary.

Motor Torque

When selecting a VFD, the starting, peak, and running torques of the motor should be considered. The motor torque available to the driven machine must exceed what the machine requires from start to full speed. The required acceleration time is also a factor to consider, which is directly proportional to the total inertia and inversely proportional to the available torque.

Load Type and Duty Cycle

Load type and duty cycle are also important factors to consider when selecting the appropriate drive. The choice of drive can be affected by whether the load is stable, variable, follows a repetitive variation cycle or has pulsating torques. The duty cycle is expressed as the ratio of on-time to the cycle period.

Temperature and Performace Elements

It is essential to consider temperature, as operating self-ventilated motors at reduced speeds may increase above-normal temperature. Finally, if the application requires performance elements such as torque control or quick speed response, a flux vector or closed-loop vector drive may be necessary instead of a volts-per-hertz drive.


Save Money, Reduce Waste, and Improve Energy Efficiency with Variable Speed Drives. Choose the Right VSD and Transform Your Business. Explore Our Collection of VSDs Today.

Variable Speed Drives (VSDs) are essential devices that regulate the speed of electric motors by changing the voltage and frequency of the power supplied to the motor. This allows adjustments to be made according to your process's requirements. VSDs offer many benefits to businesses in different industries, including energy efficiency, cost savings, improved process control, and reduced environmental impact.

In this article, we have covered the mechanics of VSDs, different types of VSDs, their benefits, real-world applications, and tips for choosing the right VSD. AC Motor Drives are the most efficient and cost-effective VSDs widely used in various industrial applications.

When selecting a VSD, it's essential to consider various factors, such as operating conditions, base speed, motor torque, load type and duty cycle, temperature, and performance elements. Choosing the right VSD can help avoid potential issues and ensure that the VSD can withstand conditions such as temperature, cooling air supply, gas, moisture, and dust.

At Industrial Electrical Warehouse, we provide various top-brand Variable Speed Drives. We deliver worldwide, with free shipping for standard shipping regardless of quantity and amount of orders. Our VSD collection is designed to meet various industrial applications, ensuring you can find the right VSD that meets your business's needs.

Product Recommendations: 

Allen Bradley PowerFlex 4 Inverter Drive 1-Phase In 230VAC 22A-A2P3N114


SEW EURODRIVE Movitrac A Inverter 400V 3 Phase 16A 10HP MC07A075-5A3-4-00


Omron MX2 Inverter Drive 2.2kW 3-Phase In 480VAC 0.1 to 400Hz Out 3G3MX2-A4022-V1

VSDs offer a reliable and cost-effective solution to improve energy efficiency, reduce maintenance costs and waste, or benefit the environment. We invite you to explore our collection of VSDs and take advantage of their many benefits.


What is a variable speed drive? (n.d.-b). Drives.

Chamberlin, R. (2012, June 11). Types of Variable Speed Drives. Precision Electric.

How to select a variable frequency drive. (n.d.). Eaton.

Variable speed drives

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