8 Things You Need to Know About Retrofitting Motors

3. Consider downsizing

Sometimes the most efficient option simply requires downsizing. Oversized motors run below their nameplate efficiency and lead to high, needless consumption of electricity.

“A lot of motors were sized when the facility was initially designed, and they’re too large,” says Glenn Andler, general manager of VitaBuilders, a professional millwright and agricultural operations services provider in Fall River, WI.

Andler explains that in the past, larger-than-necessary motors were commonly used to compensate for low efficiency levels.

“Before motor efficiency was mandated, they could be as low as 70% to 85%,” says Andler. “Many people installed large motors to get more power because electricity was inexpensive and people weren’t as concerned about energy conservation. But today, motor and drive efficiencies are much tighter, so you should always appropriately match the motor size to the equipment and application.”

Vande Hoef suggests contacting your utility company to conduct an energy audit and track how much energy a motor actually consumes. If it uses less than it was designed to, replacing it with a smaller, more efficient motor will typically produce a quick payback.

The MotorMaster+ tool can also help size a motor for a particular piece of equipment or application. Even so, Doug Post, president of Interstates Engineering, Inc., recommends contacting an engineer before any motor retrofitting project.

“Programs such as MotorMaster+ are helpful, but to a layman, it still might be difficult to correctly size a motor,” says Post. “I’d advise working with an experienced engineering or process firm because they might know, for example, that a 25-hp motor can efficiently handle a given application, even if a 40-hp was recommended elsewhere. The resulting savings over the long haul would easily pay for the consulting fee.”

4. Choose the right drive

In addition to helping right-size a motor, a process engineer may recommend a specific drive for an application. One option is a Variable Frequency Drive (VFD), which controls the speed of an electric motor by adjusting the frequency of the electrical power it supplies.

“Installing a VFD saves energy in applications where the motor should run at varied speeds at different times, or not at all,” says Vande Hoef. “For example, in a pipeline without a VFD, the motor runs at the same speed and consumes essentially the same amount of energy whether it is 30% or 100% full of fluid. Installing a VFD allows you to slow the motor to 30% speed, and saves money by consuming less energy.”

Installing a VFD also gives operators the option to put equipment in idle mode.

“With a grain elevator, one of the core functions is receiving, but all of the equipment from the dump pits to the conveyors to the bucket elevators, only needs to run while it’s receiving grain,” Vande Hoef points out. “Yet in most cases that equipment stays on continuously. With a VFD you can put the equipment into idle until a truck drives up to dump. Then it can be turned on with a button or automated with motion sensors. After the grain is conveyed and distributed to its destination, the equipment would drop back into idle and conserve energy.”

However, some grain operations do require constantly running motors for certain applications. Rexnord Industries, Milwaukee, WI, the manufacturer of Falk® gear drives, has developed a high-efficiency gear drive suitable for many applications in the feed and grain industry.

“The Falk V-Class™ gear drive incorporates unique cooling devices that are simple, maintenance-friendly and breakthrough in the ability to dissipate heat,” says Craig Franz, product service specialist, Rexnord Industries.

Jason Quackenbush, marketing manager, engineered drives for Rexnord Industries, explains the technology behind the Falk V-Class’ DuraPlate™ system.