How to Save Energy with Variable Frequency Drives

According to the Energy Information Administration, industrial motor systems consume around 25% of the electricity used throughout the United States — making motors the largest source of electricity use in the country. Unfortunately, when used on an industrial level, these essential machines can soak up resources, eat away at budgets, and even potentially damage the environment.

As the prices (both financial and environmental) of energy consumption continue to rise, the need for more energy-efficient solutions in motor control grows with them. In an effort to reduce energy-related losses, many businesses and engineers are turning to variable frequency drives — an innovative alternative to other throttling devices, such as fixed speed controllers, valves, and dampers.

Following, we will discuss how you can use variable frequency drive (VFD) solutions to control machine capacity, operating performance, and energy usage on a significant scale.

Step 1: Understand the Function of a Variable Frequency Drive

To save energy using a variable frequency drive (VFD), it’s important to first understand what it is, and what it can do. In the industry the VFD goes by various names, including adjustable speed drive, variable speed drive, inverter drive — but the underlying processes are the same.

At their core, VFDs perform a similar function to the motors they control, by converting raw energy into usable power. VFDs convert the alternating current (AC) in motors into direct current (DC); then convert DC back to AC, in such a way that it drives the motor at optimum speed.

The opportunity to control the amount of energy a motor uses — combined with the cost of electronics — has made VFDs increasingly popular amongst industries seeking meaningful savings. Of course, the amount of energy a VFD will save depends on each motor’s application. Imagine a 50 horsepower fan motor that operates 24 hours a day. You likely don’t need to run that unit at full capacity for the entire day. With the help of a VFD, you can run the unit at full capacity for only a couple of hours, and at 50% capacity during other times — quickly amounting to significant energy savings.

Step 2: Consume Only the Power You Need

A VFD allows you to consume the exact amount of energy you need, without waste. Most basic motors are unable to change their speed; their design allows them to rotate at a single, set frequency according to the supply voltage, and presence of magnetic poles within the system. It can be challenging to find a motor that offers the correct speed for a designated application. In fact, many motors are oversized on purpose, to ensure they can deal with worst-case-scenario peak loads. This presents a problem, as these fixed-speed systems are running at full capacity during all hours, even though most of the time their full capacity isn’t needed.

With a VFD, you can choose to run the motor at the energy consumption level it needs — matching the power used to existing work requirements. Rather than running at peak levels all of the time, you use energy as, and only when, you need it.

Step 3: Recover Energy with Regenerative Converters

Some VFDs save additional energy by allowing you to make the most of excess power in the system.  In applications where the process may cause regenerative loading, rather than dump the excess energy into a resistor grid for the energy to be burned off, VFDs that have been fitted with regenerative converters can recycle this excess power back into the power line.

A regenerative converter in a VFD replaces the resistor network, and dynamic braking transistor; absorbing excess energy from the system, and returning it to the AC power source. While in some cases this process may reduce overall motor efficiency, it can also lead to improved system energy efficiency, and the chance for better profits.

Step 4: Save Energy Indirectly

Often, equipment controlled with VFD solutions lasts longer, and experiences less downtime. This is because you’re providing a better environment for your motor to work; protecting it from issues such as phase problems, under-voltage, over-voltage, and electro-thermal overloads. Plus, VFDs can be set up for soft-starting and soft stopping of the load; meaning instead of subjecting the driven load to an instant shock, you can allow for smooth performance — greatly reducing wear on bearings, gears, and belts.

The Value of Variable Frequency Drives

With industrial electric motors at the core of many businesses — and using about a quarter of our nation’s electricity — it’s essential to find innovative ways to keep our motors running, while reducing and optimizing energy usage. VFDs offer one of the best ways to reduce energy waste in the industry today; but they do more than simply lower your energy costs. Companies who operate their motors at the most efficient speed for any given application are likely to experience fewer mistakes, meaning that production levels increase, and revenue thrives.

Do you use VFDs in your motor operations? Let us know in the comments below!

How to Save Energy with Variable Frequency Drives was last modified: July 20th, 2017 by admin

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Jerry is the owner of Sloan Electromechanical and is active in all aspects of the company. He is passionate about doing the work RIGHT and proposing the best product solution, hence the Sloan team is focused on aligning company values with client values. Please post your questions or comments and Jerry will respond. For a faster or confidential response, please contact Jerry directly 619-515-9691 or LinkedIn
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