Why a Variable Frequency Drive VFD is required for your HVAC System.

How an inverter is fundamental for climate control.

Since the HVAC systems are required to work continuously in any condition, the constant control of the fans guarantees the circulation of the air with no interruptions. The Variable Frequency Drive is the specific motor drive used to regulate the action of the fans in the HVAC systems, and, in this article, we will explain what it is, its role and all the benefits coming from its application.

What a variable frequency drive is.

A Variable Frequency Drive is a system that includes a motor that is able to send inputs to generate mechanical force. This inverter is often mentioned by its abbreviation VFD and is known with different names, such as adjustable frequency drive and adjustable speed drive, variable speed drive, AC drive, micro drive, inverter, drive.

What is variable frequency drive used for? The application of the variable frequency drive in HVAC systems.

A variable frequency drive is applied on small to large solutions. Users prefer VFD because reliable, efficient, and easy to find on the market. In this article, we will focus on its ability to manage fans in HVAC and AHU systems. 

Variable Frequency Drive parts: AC motor, controller, operator interface.

A VDF is composed of three different parts:

AC Motor: most of the inverters are equipped with a three-phase induction motor. 

Controller: this part converts the electricity into motion.

Operator interface: it is the interface available for the user to monitor and manage the operating speed.

How a variable frequency drive works

The process of a VFD follows different steps: the drive holds the AC voltage and frequency into the rectifier bridge with the scope of converting the voltage to DC. The converted DC voltage is filtered with the use of a capacitor bank and related inductors. In the following step, the DC voltage is inverted back to AC and sent the voltage to the motor with the requested frequency.

Why use a VFD to control fan rather than a damper

In HVAC systems, a fan motion is controlled with either a damper or an inverter. The latter is usually preferred for its energy efficiency and to deliver the same work.

How a variable frequency drive saves more energy than a damper to control a fan

When a damper is in use to control a fan, the input power decreases when there is a reduction in flow rate in an HVAC system. Different situation with Variable Frequency Drive, as the input power reduces far more when the flow rate decreases.

What is the difference between VSD and VFD?

Following the complete Dosupply's article posted on their blog, VSD and VDF have a few relevant differences that make them deliver a different type of service to be applied under different conditions.

a Variable Frequency Drive is able to handle the speed at the start-up, when the motor interrupts its work and when it is in action. The VSD, the Variable Speed Control is used to keep a specific speed. 

Also, the use of torque differs between VFD and VSD. The Variable Frequency Drive provides different levels of speed, meanwhile, a Variable Speed Drive manages a stable and constant speed.

In terms of energy efficiency, The VFD inverter requires a lower amount of energy than a VSD to control an HVAC system or AHU system and is able to connect to more than a motor. 

What is the advantage of using a variable frequency drive? When to use variable frequency drive

An Inverter is capable to control, in an AHU system or HVAC system, the speed of a fan at different levels. It is a tool that is more efficient than a VFD and a Damper as it requires less energy to work. 

The ABB drives for HVAC: the ACH580 series of inverters

The manufacturer ABB, a leader in the technology and HVAC industry, released their version of the HVAC drive, the ACH580-01, a solution that aims to provide complete climate control in environments such as industrial, commercial and offices. The ACH580-01 series of inverters are devices easy to use and set up. As with most VDF, this solution can be integrated with any type of motor. It is designed to meet all the needs a commercial or industrial environment has. This solution is able to handle different types of fluids, either air or water. This device prioritises the control of pressurization to provide fresh air and interrupt is the flow when required. The management of dampers is the core activity, the user easily defines their degree of aperture. The ACH580-01 focuses on a series of checks to make sure that all the parts of the AHU system, such as sensors and dampers, work as expected. 

The Danfoss Air handling drives

Another option is the range of Danfoss air handling drives, or inverters, designed for ceal rooms, HVAC and AHU systems to supply clean air. The Danfoss inverters offers a continous service, capable to work even in case of failure of one of its parts. These air handling inverters help reducing the energy costs when controlling a fan or a pump. The monitoration features are smooth and let the user keep the track of the fans' activity. A software feature is available to manage the efficiency. 

Conclusion

In this article, we have provided an overview of what an Variable Frequency Drive is, how it works and the applications in an HVAC system and an AHU unit. All the types of inverters here mentioned are available in their specific category, the main brands in we stock are Danfoss and ABB.

If you want to add anything relevant related to the topic or your direct experience, feel free to leave a message, we would like to hear from you.

If you need any additional info and details do not hesitate to contact us at support@i-acs.co.uk