Inverter Drives

An inverter drive is a variable speed drive that allows users to adjust the speed or output of an electric motor. It is also called an adjustable speed drive, adjustable frequency drive, frequency converter, inverter drive motor, inverter motor, and power converter. Inverter drives allow AC power to be converted to DC, providing the user with precise control. They are also ideal for helping to reduce waste or loss of electrical energy in a range of applications. Inverter drives are available in both single-phase and three-phase configurations.

What is the Difference Between VSDs (Variable Speed Drives) and VFDs (Variable Frequency Drives)?

Variable Speed Drives (VSDs) and Variable Frequency Drives (VFDs) are both essential technologies used to control the speed of electric motors, but they operate on different principles and are suited for different applications.

Variable Speed Drives (VSDs)

VSDs encompass a broad category of devices that can adjust the speed of both AC and DC motors. They achieve variable speed control through various methods, which may include:

• Mechanical Means: Some VSDs utilise mechanical components such as clutches or belts to modify the output speed. While this method can be effective, it may lead to energy wastage if the motor runs at full speed even when lower speeds are required.
• Electronic Control: Many modern VSDs employ electronic methods to control motor speed, similar to VFDs. This allows for more precise adjustments and improved efficiency. VSDs with electronic control are sometimes referred to as adjustable speed drives.

VSDs are versatile and can be used in a variety of applications, including those requiring constant torque and variable torque, making them suitable for diverse industrial environments.

Variable Frequency Drives (VFDs)

VFDs, also known as AC inverter drives, are a specific type of VSD designed exclusively for controlling the speed of AC motors. They operate by varying the frequency and voltage supplied to the motor, which allows for:

• Precise Speed Control: By manipulating the voltage and frequency applied to the motor's stator, VFDs can provide smooth acceleration and deceleration, enhancing operational efficiency.
• Energy Savings: VFDs enable motors to run at optimal speeds based on load requirements, significantly reducing energy consumption compared to systems that run at full speed continuously.
• Operational Flexibility: VFDs allow for seamless speed adjustments during start-up, operation, and stopping phases, contributing to smoother overall performance.

How Do Inverter Frequency Drives Work?

Inverter drives are controlled by inputting specific frequencies or parameters into the device. This allows for greater control over your machinery and operations with more precision. These inputs can usually be adjusted via a keypad or digital display. Some models can also be controlled remotely through networked connections. Once the inputs are set, the inverter drive then converts the incoming AC power to DC, using advanced switching techniques to create a variable frequency and voltage AC output.

Inverter drives are situated between an electrical supply and a motor, with the inverter allowing the power to be regulated to suit the application. By controlling the frequency, the inverter effectively controls the speed of the motor. Additionally, inverter drives can also manage the motor's starting and stopping characteristics, leading to smoother operation and reduced wear and tear.

Types of Inverter Drives

Inverter drives come in various types, each with distinct characteristics suited to different applications and motor control needs:

Scalar Drives

Scalar drives, also known as V/f drives, are a simple and cost-effective type of inverter drive that controls the motor speed by adjusting the voltage and frequency in a linear relationship. They are suitable for applications that don't require precise speed or torque control.

Vector Drives

Vector drives offer more sophisticated control over motor speed and torque, providing precise control and high efficiency, even at low speeds. They achieve this by controlling the motor's magnetic field vector, enabling dynamic performance and responsiveness. There are two main types of vector drives:

Voltage Source Inverter

Voltage source inverters (VSI) are the most common type of vector drive, generating a three-phase AC output voltage with variable frequency and amplitude. They offer excellent speed and torque control, making them suitable for a wide range of applications.

Current Source Inverter

Current source inverters (CSI) regulate the output current instead of voltage. While less common, they offer certain advantages in specific applications, such as high-power drives for large motors and regenerative braking systems.

Single-Phase Inverter Drives

Single-phase inverter drives are designed for applications requiring lower power levels. They are typically used in smaller devices like fans and small pumps, making them ideal for residential or light commercial use.

Three-Phase Inverter Drives

Variable frequency drives for three-phase motors are used in industrial settings where higher power is necessary. They provide better efficiency and performance for larger motors, making them suitable for demanding applications that require precise control over speed and torque.

IP Rated Inverter Drives

Inverter drives come with various Ingress Protection (IP) ratings to ensure they can operate effectively in different environmental conditions. Higher IP ratings indicate better protection against dust and moisture, making them suitable for harsh industrial environments.

Features and Benefits of Adjustable Frequency Drives

Adjustable frequency drives are versatile solutions for various applications. Here are some of their advantageous features:

• Versatile Applications: From controlling small appliances like desk fans to managing high-torque machinery, inverter motors offer flexibility for diverse needs.
• User-Friendly Operation: Digital LED input screens provide intuitive parameter setting, input, and real-time monitoring for ease of use.
• Space-Saving Design: Compact and sleek designs ensure convenient installation in various environments, even with limited space.
• Effortless Installation: Simplified setup and connection processes minimise downtime and ensure quick integration into existing systems.
• Enhanced Safety: Built-in emergency stop functions provide immediate protection against unexpected events, prioritising operator safety.
• Energy Efficiency: By optimising motor speed and performance, adjustable frequency drives help reduce energy consumption in industrial settings and homes, leading to significant savings and lower operational costs.

Applications of Inverter Frequency Drives

Inverter drives are used in a wide range of industrial applications, such as:

HVAC Systems

Inverter drives are extensively used in heating, ventilation, and air conditioning (HVAC) systems to control the speed of fans and pumps. By adjusting motor speed based on demand, they help maintain precise temperature and airflow control, improve energy efficiency, and reduce noise levels.

Manufacturing and Automation

Inverter drives are essential in manufacturing and automation, powering conveyor belts, robotic arms, and other machinery. They provide accurate speed control, smooth acceleration and deceleration, and energy savings, enhancing overall production efficiency.

Water and Wastewater Treatment

In water and wastewater treatment plants, inverter drives control pumps and motors used for pumping, aeration, and filtration processes. By adjusting motor speed based on demand, they ensure efficient and reliable operation while minimising energy consumption and contributing to water conservation efforts in industries reliant on water resources.

Mining and Material Handling

Inverter drives play a critical role in mining and material handling operations, powering conveyor systems, crushers, and other heavy machinery. Their ability to handle varying loads and provide precise speed control improves productivity, reduces equipment wear and tear, and enhances safety.

The Leading Supplier and Manufacturer of Inverter Drives

RS is a trusted supplier, distributor and manufacturer of inverter motors, featuring industry-trusted brands like Siemens, Schneider Electric, our own RS PRO line and more. From variable frequency drives for 3 phase motors to thermocouple sensors and signal barriers, we offer a comprehensive selection of automation solutions at competitive prices.

Order your inverter motor online today and enjoy next-day delivery or self-collection at your local branch. For more details on our ordering process, delivery services and delivery fees, please refer to our Ordering Page and Delivery Page.