Buying Guide: Variable frequency drives

Want to reduce energy and maintenance costs? Consider how VFDs can help motor-driven equipment like pumps and fans work more efficiently.

In every organization, there are usually energy-saving opportunities around several corners. For the fans, blowers, pumps and other motor-driven equipment that operate in organizations of all types, a simple technology can make a big difference: variable frequency drives (VFDs).

What are variable frequency drives?

VFDs are a type of variable speed drive. They control the frequency and a range of other parameters, including voltage and current of power supplied to an electric motor, to drive and change speed based on what the equipment’s process demands.
 
The technology behind VFDs is actually all around us, for example, controlling heating and cooling functions in our home furnaces and fridges. Or, think about old washing machines that would shake and make noise on the spin cycle. Today’s modern washers adjust their speed based on the load amount and electronic settings, often reducing speed to accomplish the same task as a super-fast spin cycle.
 
Well, VFDs work in a similar way but often for equipment on a much larger scale.
 
VFDs adjust a piece of equipment’s speed to ultimately do the same job, using less energy. In the case of a pump, think of it this way. If you’ve been on a beach and tried walking into the water, it’s pretty easy. But try running and it’s a lot harder – the water’s resistance increases once you speed up. So, even though you’re going faster, you’re using up significantly more power and energy to get as far as you would if you’d just walked in.  

Opportunities for VFDs

VFDs have a variety of applications across commercial and industrial spaces ranging from small devices and heating, ventilation and air conditioning (HVAC) systems, to large equipment, such as compressors, blowers, and water pumps in water treatment plants.
 
They also have applications across industries, from mines to schools to office buildings. In any place where there are pumps and fans, there are likely opportunities for VFDs to save energy.
 
Installing and getting the most out of VFDs requires the help of a qualified contractor who can look at your facility’s operational requirements, electrical system, power quality, and more to find the right VFD for your needs. Your contractor can also help you apply for incentive programs to save on your upgrade costs and get more out of your energy-saving investment.

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How VFDs improve efficiency

Ultimately, using VFDs to optimize motor controls can reduce energy consumption in a facility by as much as 70 per cent, or even more.¹
 
They can do this in several ways. For example, they can reduce the power required to start up certain motors. That means potentially less wear and tear in motors and electrical equipment, which can save costs for facilities that need to start motors during peak periods, when energy rates are higher.
 
VFDs also help better control operating speed and acceleration, which may help equipment with conveyor belts move more smoothly and efficiently.²
 
Businesses of all types are reaping the benefits of VFDs. Chesswood Arena used them to help maintain peak ice conditions in its Toronto rink – part of a series of retrofits that ultimately helped it save thousands of dollars in electricity costs.
 
Teknion, an office design and furniture manufacturer, also uses VFDs in one of its plants. In this case, the company added high-efficiency motors with VFDs to a dust collection system. As more production areas go online, the fan speed increases. Then, during periods of downtime or maintenance, it slows – a system that helps it save money, every year.
 
VFDs have several benefits beyond energy efficiency, too. With VFDs, you can potentially curb the costs of maintaining – and even replacing – equipment. Think back to that old washing machine and how often you’d have to fix it, compared to a new model with adjustable spin speeds. VFDs can have a similar impact for your equipment. They can also reduce equipment noise and vibration, potentially making for a better working environment for your team.

What to ask your contractor

To know whether VFDs will work for you, you’ll first need to understand your load requirements. VFDs are best for applications where the load requirement varies, so look to areas of the business where that’s the case. Look for areas that may have higher maintenance costs or where equipment has failed. Those may be the equipment that would benefit most from VFDs.
 
Talk to your contractor about your operations – what your motors, pumps and fans are doing – but also what you’re trying to achieve, beyond energy savings alone. For example, you may want to increase production. Or, comfort might be a bigger priority, so you may want to look at VFDs for your heating, ventilation and air conditioning first.
 
Your contractor can also help you ensure that your equipment is as efficient as it could be. Oftentimes, adjusting speed by adjusting sheaves, replacing a belt or upgrading to a higher-efficiency motor is a cost-effective way to improve energy efficiency levels before adding a VFD. You should also check that equipment such as fans and motors are the right size for the task. As a facility’s needs change over time, the original equipment may not even be right for the space anymore.
 
Finally, ask about controls for your VFDs. In some cases, you may want controls integrated into an overall building management system.
 
Whatever your operation type, if you have pumps or fans on site, a conversation with a qualified contractor about VFDs will be well worth your time.

References

¹ Unitronics – What is a VFD - Variable Frequency Drive?
² Control Engineering – VFDs: six benefits, energy efficiency