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Controlling and protecting our pump and fan motors: Modern solutions for today’s applications

End users, too, have become more sophisticated, demanding information and protection in a timely manner.


Photo: © VIEWFOTO STUDIO / Adobe Stock

October 22, 2021 – Darrell Ouellette has been with Eaton Industries (Canada) for 16 years as a technology application specialist. Based in Alberta, his specialty is finding solutions for controlling motors—a lot of which are used in pump or fan applications.

“I support the company’s industrial control product lines, both pre- and post-sales,” he tells me. “And it can be challenging, because the world is evolving at such a rapid pace.”

After some quick research, I learned motors—in some form or other—have been with us for roughly 200 years. But, as technology becomes more complex, I reached out to Darrell to learn more about how motors have evolved over the years, specifically with regard to control and protection solutions in pump and fan applications—two very important loads.

“Motors, pumps, and fans have been around a long time as primary loads. Decades ago, motors were controlled by what we call a full voltage starter,” Darrell explains. “So they would have an electrical contactor which would apply the power to the motor for starting and, when you take the power away by opening the contactor, the motor stops.”

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That basic On/Off control technology still exists, Darrell says. Where motor protection is concerned, the market employed a thermal overload to prevent the motor from operating beyond its thermal design characteristics.

“Thermal overload devices monitored the current going to the motor to calculate whether the motor was being thermally overloaded,” Darrell said. Basically, when the thermal calculation reached a certain setpoint, it would break the control circuit and stop the motor. “This technology, too, is employed today.”

When did things change?

Both full voltage and thermal overload technologies sound pretty straightforward, so what is it that’s driving sophisticated control and protection solutions in the market? Have the motors themselves become very complex, or have end user requirements and desires changed?

“Yes,” says Darrell, smiling. “All of the above.”

Motor control solutions have evolved into things like reduced voltage starting, “which are devices used for soft-starting and, possibly, soft-stopping motors—primarily in mechanical [pump and fan] applications”.

“Another evolution of motor control is using variable frequency drives. VFDs are used where you need speed control for various processes,” Darrell says, adding. “And you find a lot of these in a fan and pump applications, too. So a lot of it has to do with process control and protecting assets, which include the motor and the process being served by that motor.”

End users, too, have become more sophisticated, demanding information and protection in a timely manner.

“They wanted more features,” Darrell says. “If we look back at thermal overloads, those devices simply monitored the current going to the motor. There are certain power quality issues that can happen with a motor that may not be detected by a thermal overload, or may not be detected quickly.”

Darrell points to the issue of phase loss, as an example. “Yes, thermal overloads will eventually detect a phase loss, because current going to the motor will rise, but it would take a long time by today’s standards for anyone to know a phase loss condition is occurring. In that time, your process may have been damaged.”

So a lot of what’s driving modern control and protection strategies is the desire for timely information, which naturally leads to timely intervention when problems either occur, or are on the horizon… not to mention other bells and whistles, like current- or voltage-based monitoring.

Control and protection as insurance

“So the old methods of protecting motors are quite relevant today. There are still a lot of thermal overloads being used in the industry,” Darrell reminds me.

Historically though, he notes, there was always a gap—something missing—with thermal overloads and motor protection. “As we advanced into solid-state and digital, we got into motor protection relays, which were very large, full of features, and monitored everything”.

Unfortunately, these motor protection relays were typically only used on very large, very critical (i.e. very expensive) motors.

“So there was certainly a gap between the expensive solution and the low-end thermal overload solution, and the market wanted to see more features in a smaller protection solution that’s also cost-effective,” Darrell says. “Today, technologies have evolved to microprocessor-based control and protection, and industrial networking, to give customers products that are simple but still have a bunch of features they desire for adequate control and protection.”

Ultimately, this translates into timely motor protection.

“Pumps and fans are typically meant to go in one direction,” Darrell says, “If, for whatever reason, the utility phasing got switched [phase reversal], you would want your assets protected. Today’s control and protection solutions are capable of detecting phase reversals quickly.”

“Let’s look at a water pumping application, which is suitably protected by a thermal overload, but where customers have desired something more advanced,” Darrell explains. “What happens when the pump runs out of water? If we’re running just on the old thermal overload, it wouldn’t really know that we’ve run out of water because the motor is not thermally overloaded. But then the pump runs dry and you’ve damaged your pump.”

With the ability to monitor that motor, the end user can determine the normal operating current when water is pumping. When the current moves too far outside that setpoint (e.g. not drawing enough current), it may mean the pump has run dry. Rather than continue to run the pump to failure, an alarm can notify personnel that something is not right, and it may be prudent to shut down that pump.

“Maybe that pump is serving a condo complex. Without advanced motor protection—with monitoring and notification—your pump could run to failure, which leads to a time-consuming and costly repair, and very angry tenants.”

Just as pumps push liquids, fans push air. These systems are usually controlled by a central building management system, “and customers now want to know whether a particular fan is actually doing anything”. When it isn’t, a building’s entire ventilation system can become unbalanced.

Market options for everyone

Darrell explains there are a lot of other features available on the market today for motor control and protection, but a popular overall trend is industrial networks, where assets (like motors) can not only be started/stopped remotely, but monitored over time.

“Everybody is looking for more data to make decisions,” Darrell says. “This allows end users to trend motor data, which gives them an indication of motor condition, and helps ensure their processes are operating optimally.”

Naturally, this kind of information benefits the end user’s maintenance strategy.

“We’ve evolved thermal overloads to solid-state overloads, to what we would call motor management—control and protection, all in one. Even this is evolving, as we have begun decentralizing control so that it is employed right at the motor itself.”

“Let’s say we have a plant with a lot of motor starters in it, and there’s a power outage,” Darrell continues. “When the power comes back, we may not want all those motors to start at the same time. Historically, we could have staggered the starts in the PLC [programmable logic controller] or the DCS [distributed control system]. Nowadays, with motor management relays, we can take that control away from the PLC or DCS and leave it up to the particular motor for optimal control and protection.”

But the innovation doesn’t stop there.

“Customers are also looking for solutions that are modular, so they can buy the solution with features they need right now for their particular application, but leave room down the road to expand.”

And those additional features could be just about anything, from temperature monitoring to timers to custom control logic.

These solutions have also come down in size, such that they are no longer huge, expensive devices. They can fit quite nicely into motor control centres or in enclosed control, says Darrell. “So, space-wise, technology has evolved to the point where we can get pretty advanced protection in a small package.”

“It boils down to what the customer wants… what they expect out of a motor control and protection solution,” Darrell summarizes. “They can get started with cost-effective basics, then add features over time. Sure, the overall cost will go up, but the additional features will lead to potential savings that outweigh that cost.”


This feature—plus more great content—appears in the October 2021 edition of Electrical Business Magazine. Even more back issues are located in our Digital Archive.



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